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Sulfate is a critical component of schwertmannite. However, the sulfate content of schwertmannite decreases with the increase in AMD-polluted river pH value, and its impact on the surface properties and Cr(VI) adsorption of schwertmannite remains unclear. To address this issue, different methods, including batch adsorption, N 2 physisorption, scanning electron microscopy (SEM), potentiometric titration, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) in combination with two-dimensional correlation spectroscopy (2D-COS) analysis, and surface complexation modeling (SCM) were employed. Our results showed that sulfate existed as both non-protonated bidentate-binuclear complexes and non-protonated outer-sphere complexes in schwertmannite. The surface morphology and particle size of schwertmannite were unaffected by the sulfate content. However, a decrease in sulfate content resulted in a drop in the negative charge on the surface of schwertmannite, which is conducive to particle aggregation. An increase in pH, on the other hand, raised the negative charge and encouraged the dispersion of the particles. And then, reducing the sulfate content of schwertmannite led to a decrease in acid-base buffer and Cr(VI) adsorption capacity of schwertmannite. The adsorption process of Cr(VI) by schwertmannite can be divided into two stages. In the first stage, Cr(VI) was adsorbed primarily through anion exchange reactions with the sulfate; however, the contribution of surface complexation gradually increased as the initial sulfate content decreased because of a reduced likelihood of anion exchange and an increase in the specific surface area of schwertmannite. Additionally, the behavior of sulfate and Cr(VI) in this stage could be predicted based on the initial sulfate content of schwertmannite. In the second stage, surface complexation with hydroxyl sites became the predominant mechanism of adsorption, which still exhibited great potential at higher Cr(VI) concentrations. Finally, the aforementioned hypothesis was used to establish a CD-MUSIC model, and the fitting results demonstrated that the density and Cr(VI) adsorption capacity of the sulfate site dropped as the sulfate content decreased, while the hydroxyl site was less impacted. The findings have provided insights into further understanding the properties of schwertmannite and its adsorption of Cr(VI). [ABSTRACT FROM AUTHOR]

The sulfur–iodine (S–I) thermochemical cycle for hydrogen production can be widely applied. The solubility of I 2 in complex and non-ideal HI–H 2 O–I 2 (HI x) ternary systems is critical for the phase separation behaviour and Bunsen reactor design. A new apparatus was established to measure the I 2 solubility using potentiometric titration. Fifty-two experimental data points of the I 2 solubility in the HI–H 2 O system were obtained at temperatures ranging from 293 K to 353 K, and the molar fraction of HI ranged from 7.69% to 15.74%. A new solubility model of I 2 in the HI–H 2 O system was developed using the solid-liquid phase equilibrium theory and a local composition model suitable for electrolyte systems (ELECNRTL). The complex effect of I 2 and I− promoting the dissolution of I 2 in the HI x system was also verified, in which the short-range interaction was dominant over the long-range interaction. The parameters of the model were determined by using the experimental data obtained in this work, where the average relative deviation (ARD) of the model was 2.73%. The model was also simultaneously validated using available experimental data, with which the calculated results were in agreement. This model satisfies the application requirements of the engineering design. • A high precision I 2 solubility measurement system for HI x solution system is established. • The I 2 solubility in HI x system is measured in the range of T = 293–353 K and x HI = 7.69–15.74%. • A high accuracy solubility model is established. • The change of internal forces in the HI x system is analysed. [ABSTRACT FROM AUTHOR]

A wearable bioelectronic ion sensing device has been proposed based on the mixed electronic-ionic conductors of tungsten bronzes. The sensor features no requirement of organic ion selective membranes (ISM) for the ion recognition. This ISM-free characteristic offers the possibility for the next generation of solid ion sensor for biological applications. [Display omitted] Noninvasive and continuous monitoring of electrolytes in biofluids based on wearable biotechnology provides extensive health-related physiological information. The state-of-the-art wearable bioelectronic ion sensors depend on the organic ionophore-based solid-contact structure of potentiometric ion-selective electrodes. This structure contains two functional sensing layers, i.e., a solid contact (ion-to-electron signal transduction) and an ionophore-containing ion-selective membrane (ISM, ion recognition). However, the potential drift, biotoxicity, and expensive organic ionophores complicate practical wearable applications. These challenges intrinsically originate from the ISM. Herein, an ISM-free wearable ion sensor based on mixed electronic-ionic conductors of tungsten bronzes is reported. These materials can serve as a bifunctional sensing layer for simultaneous ion-to-electron transduction through the redox reaction of W6+/5+ and ion recognition through crystal ion exchange. The K- and Na-adjusted WO 3 disclosed Nernstian responses toward NH 4 + and H+, respectively. The selectivity is comparable to or even better than organic ionophores, such as ammonia ionophore of nonactin. Further, the on-body monitoring of sweat ammonia and pH was realized using an integrated ISM-free flexible sensor. Therefore, this work offers an ISM-free concept and emphasizes the importance of developing next-generation ISM-free wearable bioelectronic ion sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • New potentiometric uranium (VI) carbon paste electrodes were fabricated using phosphine sulfides as ionophores. • The electrodes have Nernstian response with fast response time. • The electrodes showed a high selectivity for uranium (VI) ions over a large number of possible co-existing inorganic interferences. • Uranium (VI) determination in petroleum water samples was successfully performed. Two different phosphine sulfide derivatives have been explored as electroactive materials to modify carbon paste electrodes for the accurate detection of uranyl(II) ions. The optimized electrodes based on triphenylphosphine sulfide (L1) and triisobutylphosphine sulfide (L2) responded linearly towards uranyl(II) ions within the range of 1.0 × 10-7 – 1.0 × 10-1 M. Good sensitivity (29.32 ± 0.53 and 27.99 ± 0.61 mV per decade) and detection capability up to 7.9 × 10-8 and 1.0 × 10-7 M uranyl(II) were observed for L1- and L2-based electrodes, respectively. The effect of solution temperature on uranyl(II) determination was studied within 10–60 °C. Selectivity studies showed that the electrodes are capable to discriminate uranyl(II) ions over a large number of possible co-existing inorganic interferents. Moreover, they exhibited speedy response, thermal and long-term stability, and significant reusability. Petroleum water samples spiked with uranyl(II) ions were analyzed utilizing the developed electrodes where good recovery and accuracy were achieved, demonstrating the real-life applicability of the developed electrodes. [ABSTRACT FROM AUTHOR]

Clay minerals and cyanobacteria occur ubiquitously in nature, and both independently influence trace metal cycling due to their high specific surface areas and reactivity. Although the surface reactivity of each is well-studied, the reactivity of clay-cyanobacterial aggregates has received less attention. Here, we performed potentiometric acid-base titrations and Cd adsorption experiments on various concentrations of clay-cyanobacterial aggregates using three clay minerals (kaolinite, illite, and montmorillonite) and two model planktonic cyanobacteria, the freshwater species Synechocystis sp. PCC 6803 and marine species Synechococcus sp. PCC 7002. A component additivity surface complexation modeling (CA-SCM) approach was applied to study the impacts of the aggregation processes on the total surface reactivity. Results demonstrate that the CA-SCM approach effectively predicted the acid-base titration and Cd adsorption behaviors of aggregates at low aggregate concentrations (up to 2.5 g of clay/L for acid-base titration and 0.1 g of clay/L for Cd adsorption), indicating the additivity of the reactivity for the two components. However, at higher aggregate concentrations (25 g of clay/L for acid-base titration and 10 g of clay/L for Cd adsorption), the CA-SCM approach overestimates the acid-base titration and Cd adsorption behaviors for the aggregates, indicating significant surface site blockage during aggregation. Our SEM images show that both cyanobacterial species were covered by layered clay minerals at the surfaces and formed relatively larger aggregates at high aggregate concentrations than at low aggregate concentrations. Based on the combined results, we propose that the interaction between clays and cyanobacteria is relatively weak at low aggregate concentrations (e.g., <10 g of aggregate/L), but that significant obstruction of surface adsorption sites occurs at high aggregate concentrations (e.g., >10 g of aggregate/L), possibly due to the encrustation of bacteria by clay minerals. The implication of this work is that where turbid rivers discharge into estuaries or deltas with high primary phytoplankton productivity, aggregation (or flocculation) processes will cause the depression of surface reactivity of the aggregates and lead to a decrease in metal-binding capacity. Therefore, depending on whether the trace elements are nutrients (e.g., phosphorous) or potentially toxic (e.g., cadmium), this process has the potential to impact the marine biosphere. To ground truth this hypothesis, we further analyzed the correlation between total organic carbon (TOC) content and trace metal compositions in a compiled shale database and the results show clear negative correlation between Cd concentration and the concentration of TOC, Al and Si. Although this offers only an indirect assessment of the role of clay-plankton aggregation, as a first-order test it does indeed show that the aggregation between clay minerals and phytoplanktonic bacteria in estuaries is an essential factor that influences trace-elemental cycling. [ABSTRACT FROM AUTHOR]

The ratio of sodium to calcium (Na/Ca) in foraminiferal calcite has been proposed as a proxy for salinity, yet relatively little is known about the incorporation of sodium into the shells of foraminifera. Ongoing debates include the location of Na in the calcite crystal lattice, the possibility that at least some Na might be complexed with organics, and the influence of spines/spine bases. We present new Na/Ca measurements, determined using both solution and laser ablation ICP-MS, of the planktonic foraminifera Globigerinoides ruber (white) from plankton tows and sediment traps spanning a wide salinity range (32.5–40.7 salinity units), laboratory cultures under varying carbonate chemistry, and globally-distributed core-top samples. Our results show that Na/Ca in recently living foraminifera measured by laser ablation ICP-MS is elevated by up to 5 mmol/mol (∼85%) relative to the same samples measured by solution ICP-MS (the same comparison for Mg/Ca shows excellent agreement between the techniques). Na/Ca in recently living foraminifera measured by laser ablation ICP-MS displays a significant relationship with salinity above ∼36 salinity units with a slope of ∼0.7 mmol/mol/salinity unit; however, only a weak relationship is observed between salinity and Na/Ca measured by solution ICP-MS. We propose that Na is incorporated in at least two discrete phases; a primary phase within the CaCO 3 mineral, and a (or likely multiple) secondary phase(s). Possibilities for these secondary phases include residual metastable CaCO 3 , fluid inclusions, high Na/Ca spine bases, and organics. These secondary phases contribute to spatially-resolved analyses (i.e. laser ablation ICP-MS) of recently living foraminifera but are removed by crushing/oxidative cleaning for solution ICP-MS, and during early diagenesis, as evidenced by the agreement between laser analysis of coretop samples and Na/Ca measured by solution. The amount of one of these secondary phases, or the amount of Na within this phase, appears to vary as a function of salinity, and is likely the principal driver of the previously observed steep Na/Ca-salinity relationship in recently living foraminifera analysed by laser ablation. Overall, we find salinity, temperature, carbonate chemistry, and bottom water saturation state (Ω calcite) all have a significant but relatively weak effect on Na/Ca in the primary calcite phase. As such, Na/Ca in planktonic foraminifera recovered from sediment cores is unlikely to find widespread utility as a salinity proxy. [ABSTRACT FROM AUTHOR]

Selective detection of nitric oxide (NO) is a challenge for automotive exhaust monitoring systems due to the instability of sensing architectures operating under extreme environments. Herein, yttria-stabilized zirconia (YSZ) solid-electrolyte-based electrochemical gas sensor was developed using double perovskite electrodes (DPO) for selective detection of NO. The La 2 MMnO 6 (M: Co, Cu, Zn) phases were synthesized by sol-gel processing of constituent salts and characterized for physicochemical and sensing properties to investigate the impact of transition metal cations present in octahedral environments on charge transport properties. The La 2 ZnMnO 6 with a predominant Zn2+–Mn4+ charge ordering excelled in the sensing characteristics with high sensitivity (33 mV/decade for 3–80 ppm NO concentration), fast response/recovery time (52/42 s) and significant NO selectivity at 500 °C. The sensing behavior of double perovskites was comprehensively explored and found to abide by the mixed-potential model. Moreover, stable sensing properties over a period of three weeks indicate the here-described sensors to be potentially competitive for onboard exhaust monitoring in automobiles. • Double perovskite oxide (DPO) electrodes for nitric oxide (NO) sensor. • La 2 ZnMnO 6 DPO shows sensitivity of 33 mV/decade for 3–80 ppm NO concentration. • Response/recovery time of 52/42 s and verified stability over 3 weeks. • Sensing mechanism explained by the mixed-potential model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Depletion factor, f d : analyte fraction stripped from electrode at constant current. • Full depletion only corresponds to the limiting case f d = 1. • f d can be computed from electrode radius, transition time and diffusion coefficient. • To obtain accurate charges for Zn/In with HMDE drop 1, use transition times >5 s. • Practically, total depletion is reached with the rotating disc electrode. Several electroanalytical techniques (such as Absence of Gradients and Nernstian Equilibrium Stripping, AGNES) need to quantify the amount of reduced analyte (M0) pre-concentrated in a mercury electrode. Among the used means for this quantification, Stripping ChronoPotentiometry, SCP, also known as Potentiometric Stripping Analysis (PSA), yields the time (τ) during which a constant total stripping current can progressively empty M0 from the electrode. The depletion factor (f d) is defined as the fraction of the total analyte that is depleted while the attainment of the constant total stripping current is possible. Full depletion only corresponds to the limiting case f d = 1. For (hemi)spherical electrodes, an analytical expression for f d is derived, which depends on the transition time τ, the electrode radius and the diffusion coefficient (but not explicitly on the total stripping current or the total charge). The theoretical expectations have been experimentally checked here with the Hanging Mercury Drop Electrode (HMDE) and the Thin Mercury Film Rotating Disc Electrode (TMF-RDE) for zinc and indium as analyte metals. In the case of the smallest drop in HMDE, for accurate total charge determinations, it is recommended to work with transition times longer than 5 s. In HMDE drops, the direct use of short transition times as analytical signals directly proportional to the free metal ion concentrations (in AGNES) might be inaccurate. Computing the charge with the depletion factor would be essential in such cases. [ABSTRACT FROM AUTHOR]

Bacterial cell surface amine binding sites can form strong complexes with both toxic metal cations and anionic contaminants, thereby affecting the behavior of these contaminants in both natural and engineered systems. In this study, a novel approach was developed to measure the concentration of total amine sites on bacterial cell surfaces by combining selective site-blocking, potentiometric titrations and surface complexation modeling. Our controls show that the amine blocker sulfo-N-hydroxysulfosuccinimide acetate (SNHS) selectively reacts with primary and secondary amine sites but does not react with other binding sites on the bacterial cell surface. Amine site concentrations on bacterial cell surfaces, therefore, can be measured as the difference between the total site concentrations of un-blocked and SNHS-blocked bacterial samples. We measured amine site concentrations on Bacillus subtilis and Pseudomonas putida of 52 ± 5 and 78 ± 6 μmol/g, respectively, which account for 24% and 32% of the total binding sites on each bacterial surface. Our results suggest that amine sites can be present in relatively high concentrations on bacterial surfaces, and further studies that are focused on the role of cell surface amine sites on the transport and bioavailability of toxic metal cations and anionic contaminants are crucial. [ABSTRACT FROM AUTHOR]

Quantification of trace amounts of iron is of great importance in various fields. In the industrial sector, it is crucial to monitor the release of iron out of corrosion, pickling treatment, and steel manufacturing to address potential environmental and economic challenges. In biological systems, despite its indispensability, it is essential to maintain iron concentration below a specific threshold. Electrochemical (EC) methods provide significant analytical capabilities due to their simplicity, ease of use, and cost-effectiveness. This review focuses on the fundamental principles of EC methods for iron detection, including potentiometry, amperometry, coulometry, voltammetry, and electrochemical impedance spectroscopy (EIS). It further explains the process of obtaining calibration curves, and subsequently, determining the concentration of unknown ions. Additionally, technical notes are presented on selecting the initial signal value, reducing the duration of tests, excluding non-faradaic signals, and extending the linear region with the lowest detection limit. These notes are supported by key findings from relevant case studies. [Display omitted] • Electrochemical methods for the analysis of iron cations are investigated. • The methods are assessed for their capability to detect low concentrations of iron. • Theories on the conversion of output signal to cation concentration are presented. • Details about plots of E-i, E-t, i-t, and calibration graphs are presented. • Technical notes on how to enhance sensitivity and selectivity towards iron are explored. [ABSTRACT FROM AUTHOR]

• Direct measurements provided insights into autoprotolysis and ionization thermodynamics in protic ionic liquids. • A notable finding: Brønsted acidity of Tf 2 NH is stronger than TfOH by 2 pH units. • An entropic factor causes the difference in Brønsted acidity between Tf 2 NH and TfOH. • The constituent cations and anions of protic ionic liquids govern the ionization thermodynamics. Bis(trifluoromethanesulfonyl)amide (Tf 2 N−) and triflate (TfO−) are commonly used anions of protic ionic liquids (PILs). They are the conjugate anions of strong acids, Tf 2 NH and TfOH, whose Brønsted acidities crucially influence the performance of the PILs. In this study, the Brønsted acidity of Tf 2 NH and TfOH was compared directly through potentiometric titrations carried out in the ionic liquids of ternary ammonium salts. As a result, Tf 2 NH exhibits stronger Brønsted acidity than TfOH by approximately 2 pH units. Furthermore, calorimetric titrations revealed that this difference originates from differences in their entropy states. This suggests that the solvation state, rather than the properties in their isolated state, has a more significant impact on the acidities of Tf 2 NH and TfOH. Besides, ionization thermodynamics turned out to be governed by both the constituent cations and anions of the PILs. Therefore, once the acid-base natures of the constituent ions are characterized, the overall acid-base behavior of the PIL may become predictable. [ABSTRACT FROM AUTHOR]

Binder free spinel Co >0.5 Mn 0.1-0.3 O 0.1-0.4 @rGO composite electrode films were fabricated via galvanostatic electrochemical deposition technique over α-Fe(110) as current collector for hybrid supercapattery. Self-designed, n-MOSFET embedded ATMega328P microcontroller assisted modules were deployed to record the chronopotentiometric as well as galvanostatic charging-discharging analysis for specific capacitance (C s) measurements. Partial, exchange as well as limiting current densities(i L) and cathodic current efficiency were estimated. Electrochemical signature was analyzed from cyclic voltammetry data. Morphology and chemical nature of the composites were scrutinized with scanning electron microscopy, X-ray photoelectron, FT-IR and Raman spectra. Indigenously designed computer simulation programs coded in Python were used to optimize the deposition parameters and to analyze the crystalline structure from XRD data. The unit cell length for the FCC crystal with an octahedral geometry was ∼ 4.28 Å. An in-depth analysis of potentiodynamic polarization as well as electrochemical impedance spectral data were carried out to scrutinize the corrosion resistance and capacitance characteristics of the composites in KOH. From the Tafel constants, E corr , I corr , R u , R CT and Z W data, it was accentuated that rGO incorporated composite films offer enhanced corrosion protection for Fe(110) substrates than their individual counterparts along with augmented specific capacitance. Estimated C s was about 1166 F.g−1 at a scan-rate of 10 mV.s−1. Impact of time-constant (τ) and current density over C s was analyzed via GCD technique and was about 1458.73 F.g−1 at 2 τ and at 0.5 A.g−1. And the corresponding specific energy and power density were about 183.23 W.h.kg−1 and 237.75 W.kg−1 respectively. These composite electrode films impregnated with rGO not only improved the specific capacitance but also imparts the sacrificial corrosion resistance over the α-Fe(110) as current collector in presence of OH−as electrolyte and can serve as a sustainable electrode material for supercapatteries. [ABSTRACT FROM AUTHOR]

Direct ammonia-fed fuel cells (DAFCs) are well known for sustainable energy production. However, the issue is a certain amount of unreacted NH 3 fuel is obtained at the outlet. Thus, real-time monitoring and quantification are of utmost importance, nevertheless, this is troublesome due to the harsh thermodynamic conditions. This work aims to develop a mixed-potential sensing electrode for the detection of NH 3 under reducing conditions (H 2 atmosphere) at high temperatures. In this regard, a strontium molybdate (SrMoO 4) sensing electrode (SE) is a potential solution due to its physical and chemical stability, along with its sensitivity to NH 3 under reducing conditions. Therefore, an SrMoO 4 -based mixed-potential sensor is fabricated herein using yttria-stabilized zirconia (YSZ) as the electrolyte and platinum (Pt) as the reference electrode (RE) and is operated at 400–650 ℃. The maximum response exhibits about –21.57 mV toward 80 ppm NH 3 at 500 ℃. Further, the sensitivity is –17.19 mV/decade towards 10–60 ppm and –45.33 mV/decade towards 60–320 ppm NH 3 under 75% H 2 balanced by N 2 at 500 ℃. The as-fabricated sensor also has good selectivity towards NH 3 and good cross-sensitivity towards other interfering gases and is stable in long-term repeated operation. The direct current (DC) polarization curves and electrochemical impedance spectroscopy (EIS) results demonstrate the sensing mechanism in accordance with the mixed-potential theory. [Display omitted] • SrMoO 4 sensing electrode is proposed for NH 3 sensing in reducing conditions. • Novel approach of NH 3 sensing in the low pO 2 conditions at high temperature. • SrMoO4-based sensor's sensitivity was −45.33 mV/decade towards 60–320 ppm at 500 ℃. • Good cross-sensitivity and selectivity towards NH 3 under 75% H 2 balanced by N 2. • Fabricated sensors were operated by following mixed potential sensing mechanisms. [ABSTRACT FROM AUTHOR]

In this study, we investigated the adsorption of Cd(II) and the biosynthesis of CdS quantum dots (QDs) mediated by cells of sulfate-reducing bacteria before and after the removal of EPS to determine whether EPS or the cell wall plays a major role. Potentiometric titration revealed that the concentration of proton-active binding sites on cells with EPS (EPS-intact) was notably higher than that on cells without EPS (EPS-free) and that the sites were predominantly carboxyl, phosphoryl, hydroxyl, and amine groups. The protein content in EPS-intact cells was higher, and thus the Cd(II) adsorption capacity was stronger. The CdS QDs biosynthesized using EPS-intact possessed better properties, including uniform size distribution, good crystallinity, small particle size, high fluorescence, and strong antimicrobial activity, and the yields were significantly higher than those of EPS-free by a factor of about 1.5–3.7. Further studies revealed that alkaline amino acids in EPS play a major role and serve as templates in the biosynthesis of QDs, whereas they were rarely detected in the cell wall. This study emphasizes the important role of EPS in the bacterial binding of metals and efficient recycling of hazardous waste in water. [Display omitted] • Successful preparation of EPS-intact and EPS-free cells. • EPS play a more dominant role in mediating the synthesis of CdS QDs than cell wall. • EPS-mediated synthesis of CdS QDs has stronger ability and higher yield. • Alkaline amino acids act as biological templates in the synthesis of CdS QDs. [ABSTRACT FROM AUTHOR]

Primary processes of light energy conversion by Photosystem II (PSII) were studied using femtosecond broadband pump-probe absorption difference spectroscopy. Transient absorption changes of core complexes isolated from the cyanobacterium Synechococcus sp. PCC 7335 grown under far-red light (FRL-PSII) were compared with the canonical Chl a containing spinach PSII core complexes upon excitation into the red edge of the Q y band. Absorption changes of FRL-PSII were monitored at 278 K in the 400–800 nm spectral range on a timescale of 0.1–500 ps upon selective excitation at 740 nm of four chlorophyll (Chl) f molecules in the light harvesting antenna, or of one Chl d molecule at the Chl D1 position in the reaction center (RC) upon pumping at 710 nm. Numerical analysis of absorption changes and assessment of the energy levels of the presumed ion-radical states made it possible to identify P D1 +Chl D1 − as the predominant primary charge-separated radical pair, the formation of which upon selective excitation of Chl d has an apparent time of ∼1.6 ps. Electron transfer to the secondary acceptor pheophytin Pheo D1 has an apparent time of ∼7 ps with a variety of excitation wavelengths. The energy redistribution between Chl a and Chl f in the antenna occurs within 1 ps, whereas the energy migration from Chl f to the RC occurs mostly with lifetimes of 60 and 400 ps. Potentiometric analysis suggests that in canonical PSII, P D1 +Chl D1 − can be partially formed from the excited (P D1 Chl D1)* state. • Femtosecond absorption changes of far-red light grown photosystem II are resolved • Formation of the primary ion- radical pair P D1 +Chl D1 − proceeds at ∼1.6 ps • Electron transfer to the secondary acceptor pheophytin Pheo D1 proceeds at ∼7 ps • Energy migration from Chl f to the RC occurs with lifetimes of 60 and 400 ps • Energy levels of ion-radical states in FRL-PSII and canonical PSII are estimated [ABSTRACT FROM AUTHOR]

• A novel grouting material based on FCSA cement was developed. • The performance of grouting material in protecting anchor was investigated. • The grouting material exhibit the exceptional seawater corrosion resistance. Grouting materials play a critical role in anchoring structures of cross-sea tunnels by safeguarding the anchors against seawater corrosion and enhancing durability. In this paper, a novel grouting material comprising ferrite-rich sulfoaluminate cement (FCSA), ordinary Portland cement (OPC), anhydrite and limestone were prepared. Accelerated corrosion immersion tests were conducted to assess the corrosion resistance of the grouting material using artificial seawater solutions with varying salt concentrations. Pull-out tests were performed to verify the material's performance, while potentiometric titration and X-ray diffraction (XRD) analysis were employed to analyze free chloride ion concentration (C f) and corrosion products at the anchorage interface. Results indicate that after 1.5 years of corrosion in seawater with different salt concentrations, the bond strength stabilized at 1.05 MPa. No rust was observed on the anchor surfaces and the C f exhibited a linear increase with salt concentration. The content of Friedel's salt increases with salt concentration, demonstrating adequate chloride ion binding capacity. The test results validate the exceptional seawater corrosion resistance and long-term stability of the novel grouting material. [ABSTRACT FROM AUTHOR]

• Robust and efficient synthesis of 2,2,3,3-tetrafluoro-γ-aminobutyric acid (F4-GABA) is described. • The title compound was prepared in 9 steps in 41 % overall yield on up to 20 g scale. • The pKa values were decreased by 1.6 and 6.0 units for the COOH and NH3+ groups, respectively, upon flurination. • Differences in the conformational behavior were revealed in solid state and DMSO solution. Synthesis of 2,2,3,3-tetraftluoro-γ-aminobutyric acid (tetra F-GABA) starting from commercially available 2,2,3,3-tetrafluorobutane-1,4-diol is described. The straightforward nine-step reaction sequence allowed the production of up to 20 g of the target amino acid in 41 % overall yield. Potentiometric titration revealed increased acidity of both ionizable moieties in the title compound (the p K a values were diminished by 1.6 and 4.0 units for the COOH and NH 3 + groups, respectively, as compared to parent GABA). X-ray diffraction studies and DFT calculations demonstrated different preferential conformations in solid state and solution, although the fluorine gauche effect was observed in both cases. [Display omitted] [ABSTRACT FROM AUTHOR]

A dual sensitive, simple, and rapid membrane-based potentiometric sensor was developed to determine thorium (Th) ion in nuclear fuel samples which does not require any prior chemical separation of other matrix elements. Sensor was prepared by incorporating N,N,N',N',N",N" -hexa- n -octylnitrilotriacetamide (HONTA) in a polyvinyl chloride (PVC) matrix in presence of 2-nitrophenyl octyl ether (NPOE) and sodium tetraphenyl borate (NaTPB). The optimum membrane composition was found to be 14.1% HONTA, 3.2% NaTPB, 54.9% NPOE, 27.8% PVC, which showed a dual sensitive linear region in the calibration plot with sub-Nernstian and super-Nernstian slopes of 12.1 ± 0.4 mV/decade and 71.7 ± 3.5 mV/decade, respectively, with the corresponding linear dynamic ranges of 2.0 × 10−5 to 5.3 × 10−4 M and 3.8 ×10−3 to 1.4 × 10−2 M, respectively. The super-Nernstian sensitivity exhibited by the sensor increases with Th(IV) as well as HONTA concentrations in the membrane and can be thought to be due to micelle-mediated selective adsorption (MMSA) sensing of the metal ion. Solution speciation of Th(IV) in acetate buffer was determined by laser desorption/ionization mass spectrometry (LDI-MS) and Medusa software. Pristine and used membranes were characterized by Fourier transform infrared (FTIR), scanning electron microscopy–energy dispersive x–rays (SEM-EDS) and small angle neutron scattering (SAXS). Thorium was measured in an actual (Th–U) mixed solution and in a synthetic advance heavy water reactor (AHWR) fuel sample. The present study describes a new approach for the detection of Th(IV) ion through MMSA in an ion selective electrode (ISE). [Display omitted] • A highly sensitive and selective potentiometric sensor for Th estimation was developed. • Sensor exhibited dual sensitivity with sub and super-Nernstian slopes in calibration plot. • Aggregation of the ionophore has been observed from SAXS studies in the membrane. • Micelle mediated selective adsorption (MMSA) mechanism is proposed for sensing. • Sensor can determine thorium in mixed (Th 0.9 –U 0.1)O 2 samples without separation of other elements. [ABSTRACT FROM AUTHOR]

The stability constants of Sm3+, Ho3+ and Y3+ complexes with EDTMP have been determined by the combination of potentiometric and spectrophotometric methods. [Display omitted] • The stability constants of Sm3+, Ho3+ and Y3+ have been determined by the combination of potentiometric and spectrophotometric methods. • These data have been compared with the data given from the literature. • The discrepancy between the data of various authors has been solved. In connection with a study of 153Sm and 90Y complexes as potential radiopharmaceutical agents, the stability constants of those formed with EDTMP (ethylenediamine-N,N,Ń,Ń-tetra(methylenephosphonate)) were calculated using data from potentiometric and spectrophometric titrations measured at 25 °C in 0.1 mol/l NaCl. The following values were obtained for the stability constants of the Sm3+ − EDTMP complexes SmH -1 L6-, SmL5-, HSmL4-, H 2 SmL3-, H 3 SmL2- and H 4 SmL-: log β = 7.56, 19.08, 27.75, 34.76, 40.16 and 45.55 respectively. The corresponding stability constants of the Y3+ − EDTMP complexes YH -1 L6-, YL5-, HYL4-, H 2 YL3-, H 3 YL2- and H 4 YL- were log β = 10.47, 19.96, 28.13, 35.06, 40.35 and 46.13. A diagram of the complexes speciation dependence on pH shows that the complex forms HML4-and H 2 ML3- (M = Y or Sm) are characteristic of the pH range 6–8, which is suitable for application into the human body. [ABSTRACT FROM AUTHOR]

Tritium Breeding Modules (TBMs) aim to demonstrate tritium self-sufficiency for future fusion reactors. These modules operate at high temperatures, requiring stable, real-time and high-temperature monitoring of the tritium production and its related safety aspects. Electrochemical sensors based on perovskite-type materials are great candidates since they present good chemical stability and mechanical strength, among others. This work describes the development of electrochemical hydrogen sensors based on perovskite-type ceramic BaCe 0.6 Zr 0.3 Y 0.1 O 3-α (BCZY). Two different technologies were used for the ceramic shaping: Cold isostatic pressing (CIP) and 3D printing. CIP was selected as a well-established technique known for its effectiveness in ceramic shaping. On the other hand, 3D printing was chosen for its suitability in determining the desired geometry through rapid and efficient prototyping. The response of the sensors was evaluated at 400, 500 and 600 °C using hydrogen calibration mixtures in argon in a potentiometric mode. These results suggest that both, CIP and 3D-printed BCZY sensors have the ability to detect hydrogen in these environments, enabling a game-changing solution for monitoring fusion processes which require the quantification of hydrogen isotopes. [ABSTRACT FROM AUTHOR]

Four as-received carbon blacks from a Black Pearl family with surface areas between 30 and 1600 m2 g−1 were chosen to be tested as oxygen reduction catalysts in an alkaline environment. As main descriptors of their performance an onset potential, electron tranfer number and kinetic current density have been chosen. Even though the onset potential was smaller than that on Pt/C, the electron transfer number and kinetic current density reached the values measured on Pt/C. To find surface features governing the good performance, porosity and surface chemistry of the samples were evaluated in detail using nitrogen adsorption, thermal analysis, potentiometric titration, and XPS. The results indicated the linear dependence of the onset potential and electron transfer number on the surface area/porosity. The most porous sample exhibited an excellent catalytic behavior due to its developed ultramicropores. They attracted O 2 from an electrolyte and, through strong adsorption forces, contributed to the brake of oxygen-oxygen bonds and thus to its further reduction and protonation. The importance of the surface affinity to attract oxygen for ORR was demonstrated by linear dependences of both the electron transfer number and onset potential on the extent of oxygen adsorption from its saturated solution. [Display omitted] [ABSTRACT FROM AUTHOR]

The feasibility of using Zr-porphyrins as ionophores selective towards lactate ions was examined. Zr-tetraphenylporphyrin (Zr-TPP) and Zr-octaethylporphyrin (Zr-OEP) were tested in polyurethane membranes plasticized with dioctyl sebacate or o-nitrophenyl ether and containing cationic or anionic lipophilic sites, respectively. The best lactate response characteristics were registered for membrane plasticized with dioctyl sebacate and doped with Zr-TPP and cationic lipophilic sites. Classical electrodes with this membrane showed high selectivity towards lactate ions with a sensitivity of −76.6 mV dec−1 and linear lactate calibration range from 10−4 M to 10−1 M. Polymeric membranes containing Zr-TPP were then drop-casted on screen-printed transducers with electrodes made of graphene-containing paste. It was found that the potentiometric behavior of these miniature planar sensors is very similar to classical electrodes. In the next step, fully printed sensors, with both graphene electrodes and ion-selective polymeric membranes, were fabricated using aerosol jet printing. The sensitivity of these electrodes towards lactate was −79.01±0.39 mV dec−1 with a linear response range from 10−3.5 M to 10−1 M and a fast response to lactate concentration changes. The proposed electrode demonstrates a rare example of a potentiometric, non-enzymatic sensor for the determination of lactate ions, with the possibility of miniaturization and mass fabrication using printing methods. • Zr-porphyrins show high selectivity towards lactate ion in polyurethane membranes. • Both neutral carrier and charged carrier mechanism are possible for these ionophores. • Fully printed, planar sensors for lactate determination were developed. • A rare example of potentiometric, non-enzymatic lactate sensor was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 absorption in NaOH solution is experimentally studied in FKSM. • FKSM has higher absorption performance with lower Δ P than that of Ross LPD. • Empirical correlations of pressure drop are obtained with/without reaction. • The energy consumption performance of FKSM is evaluated. • The scrubbing factor in FKSM has a wider range of 0.267–0.689 mol/mol·L. The mass transfer processes of multi-phase flow are extensively studied in energy, chemical engineering, and production fields. The carbon dioxide absorption efficiency (y CO 2) is utilized to evaluate the mass transfer performance of the static mixer with four twisted leaves (FKSM) and the Ross LPD in NaOH-CO 2 system under different operating conditions. The automatic potentiometric titration method is applied to analyze carbonate concentration in the samples. Meanwhile, the pressure drop (Δ P), specific power consumption (E CO2), and volume-averaged energy dissipation rate (ε) are used to evaluate the energy consumption performance of the FKSM. The experiment empirical correlations among Darcy friction factor (f), liquid superficial velocities (U L) and gas superficial velocities (U G) are proposed under NaOH-CO 2 and Water-Air systems. The predictions have better accuracy with the maximum deviations of ± 1.2 % and ± 0.61 %, respectively. The ideal absorption efficiency could be obtained after seven segments with lower power consumption. The optimized condition can be obtained at U L = 0.362 m/s and U G = 0.169 m/s with E CO2 = 60.1 kWh/tCO 2. Additionally, the absorption performance of FKSM is evaluated by the scrubbing factor (S F). The estimated range of the S F is 0.267–0.689 mol/mol·L. Because of insufficient investigation on bubble swarm evolution with chemical reaction, the effect of FKSM elements number on the flow patterns and bubble distribution in the visualization pipeline will be explored in the future. [ABSTRACT FROM AUTHOR]

Miniaturization and mass-production of potentiometric sensor systems is paving the way towards distributed environmental sensing, on-body measurements and industrial process monitoring. Inkjet printing is gaining popularity as a highly adaptable and scalable production technique. Presented here is a scalable and low-cost route for flexible solid-contact ammonium ion-selective electrode fabrication by inkjet printing. Utilization of inkjet-printed melamine-intercalated graphene nanosheets as the solid-contact material significantly improved charge transport, while evading the detrimental water-layer formation. External polarization was investigated as a means of improving the inter-electrode reproducibility: the standard deviations of E 0 values were reduced after electrode polarization, the linear region of the response was extended to the range 10−1–10−6 M of NH 4 Cl and LODs reduced to 0.88 ± 0.17 μM. Finally, we have shown that the electrodes are adequate for measurements in a complex real sample: ammonium concentration was determined in landfill leachate water, with less than 4 % deviation from the reference method. [Display omitted] • Flexible solid contact NH 4 +-selective electrodes were fabricated by inkjet printing. • Melamine-intercalated graphene nanosheets were inkjet printed as a solid-contact. • External polarization improved inter-electrode reproducibility and drift. • A wide dynamic range and low LODs were exhibited. • Ammonium was determined in a complex sample - landfill leachate water. [ABSTRACT FROM AUTHOR]

Seawater calcium ion (Ca2+) concentration was investigated based on the potentiometric titration method during the summer of 2018 in the Bohai Sea, China. The measured Ca2+ concentration ranged from 7760 to 9739 μmol kg−1 and deviated from the theoretical Ca2+ values, which were estimated from the calcium/salinity ratio. The excess calcium (Ca2+ excess) ranged from 186 to 1229 μmol kg−1, showing a decreasing trend from the estuary to the nearshore, and then the offshore areas. Riverine input was an important source of seawater Ca2+ excess in the Bohai Sea. Biological activity was another factor in regulating seawater Ca2+ excess by precipitation in the Yellow River estuary and dissolution in other area of the Bohai Sea. Furthermore, the aragonite saturation state (Ω arag) values calculated from the measured Ca2+ concentrations showed a significant deviation from the values calculated from the theoretical Ca2+ concentrations, especially in the estuarine area with a maximum difference of 18.5%. Therefore, the disregard of the calcium addition would lead to an underestimation of the calcium carbonate saturation state and a deviation in the assessment of ocean acidification in marginal seas. • The seawater Ca2+ in the Bohai Sea exhibited a significant non-conservative behavior. • Riverine input was the most important source of seawater Ca2+ excess in the Bohai Sea. • Biological processes regulated Ca2+ excess by precipitation in the Yellow River estuary and dissolution in other areas. • In estuaries, there were large differences between the Ω arag calculated from measured and theoretical Ca2+ concentrations. • Ignoring the calcium addition would lead to an underestimation of the Ω arag in marginal seas, especially the estuaries. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel all solid state favipiravir selective potentiometric sensor was constructed. • The favipiravir-tetraphenylborate was synthesized and used an electroactive material. • The sensor had ultrafast response, great selectivity, and good reversibility. • The detection limit of the sensor for favipiravir was quite low. • Favipiravir content of some antiviral drug samples was successfully determined. In this study, a novel all-solid-state electrochemical sensor based on favipiravir-tetraphenylborate (FAV-TPB) electroactive material was developed and reported for FAV's highly selective and sensitive potentiometric determination in COVID-19 antiviral drug formulations. All-solid-state FAV selective sensor was fabricated by mixing and properly pressing FAV-TPB, graphite (G), multi-walled carbon nanotube (MWCNT), and paraffin oil (PO). In order to obtain the best sensor response, the sensor component ratios were optimized. The most satisfying response characteristics was obtained with the sensor composition FAV-TPB:G:MWCNT:PO in the ratio 32.5:42.5:5:20 (w/w %). The developed sensor displayed a wide linear near-Nernstian response to FAV over the concentration of 1.0 × 10−6 − 1.0 × 10−1 molL−1 with a slope of 53.6 ± 1.4 mV (R2 = 0.9997). The detection limits of the sensor was calculated as 6.0 × 10−7 molL−1, respectively. The dynamic response time of the sensor was 7 s, and the sensor exhibited fairly reproducible potentiometric responses. In the pH range of 6.0–8.0, the sensor's potential response was not affected by the pH change of the test solutions. The improved sensor had a wide temperature tolerance, and its response remained unchanged in the 10–40 ℃ temperature range. The interference effect of some chemical and biological species was evaluated by the matched potential method and separate solution method. The sensor worked stable for 12 weeks without any considerable change in its potential response. The analytical applications of the sensor were successfully carried out with the potentiometric titration of FAV with sodium tetraphenylborate solution and also the direct determination of favipiravir in COVID-19 antiviral drug formulations. [ABSTRACT FROM AUTHOR]

The integration of electronic sensors into single-use systems for bioprocessing is challenged by their sensitivity to sterilizing γ-irradiation. This challenge also applies to reference electrodes (REs), whose potentials may be destabilized upon ionization and drift over time. Here we evaluate the performance of thin-film Ag/AgCl REs over a two-month window following γ-ray sterilization using a 60Co source. γ-REs display a characteristic voltage decay during the first few weeks of operation ascribed to dissipation of radiation-induced charge defects, followed by long-term potentiometric stability when stored in phosphate-buffered saline with a 95 % confidence interval of 4 mV over 60 days. γ-REs have a mean insensitivity (inertness) of 0.6 mV/decade in pH buffers (4.5–9.0) and <1 mV/decade in the presence of organic solutes and ions at physiological ionic strength. γ-REs paired with thin-film working electrodes (WE) form sensors with near-Nernstian sensitivity, and irradiation of a thin-film pH sensor (γ-pH/WE plus γ-RE) produces a logarithmic voltage decay that is readily corrected by a single-point calibration function. The γ-irradiated sensor can monitor pH changes in sterile cell culture media over a 3-week period and produces readouts with a mean deviation below 0.04 pH units relative to a commercial meter (ground truth). [Display omitted] • γ-sterilized thin-film pH sensors perform reliably with low materials cost. • γ-irradiated sensors only need single-point calibration after conditioning. • γ-irradiated thin-film sensors can be used for 3 weeks in sterile culture media. • γ-irradiated thin-film sensors produce values within 0.04 units of ground-truth pH. • Irradiated reference electrodes show same inertness as controls over 60 days. [ABSTRACT FROM AUTHOR]

[Display omitted] • Potentiometric method for TAN determination free of chloride salt interference. • Micellar solubilization of acidic compounds of crude oil in O/W nanoemulsions. • The potentiometric method was applied to different types of crude oil samples. • Ca, Mg, and Sr salts in crude oil did not affect TAN determination. The determination of the total acid number (TAN) of crude oils is of great importance in the petroleum refining industry for evaluating the corrosion potentials of oils. The presence of salts CaCl 2 and MgCl 2 at concentrations higher than 100 mg kg−1 in crude oil can interfere with some standard methods used to measure the TAN; thus, CaCl 2 and MgCl 2 salts can hinder the accuracy of TAN determination. In this work, a new method based on the potentiometric titration of O/W nanoemulsions (NMS_TAN) was developed to eliminate the interference of CaCl 2 and MgCl 2 on TAN determination. This method is based on the potentiometric titration of oil-in-water (O/W) nanoemulsions formed via the micellar solubilization of the acidic compounds of crude oil with KOH in propan-2-ol. The O/W nanoemulsion was prepared using ultrasound and a nonionic surfactant (Tween 80). The accuracy of the method was evaluated by recovery tests, and the interferences of the mixture of salts NaCl, CaCl 2 , MgCl 2 , and SrCl 2 in the determination of TAN using NMS_TAN were investigated. NMS_TAN was employed to determine the TAN of 15 oil samples (American Petroleum Institute gravity: 13.2–38.3), and the results were statistically compared with those of standard methods. The accuracy of the NMS_TAN method was not affected by the presence of salts in the crude oil samples. Recoveries from a sample spiked with hexanoic acid ranged from 95.0 % to 100.3 % of the theoretical values. The TAN of crude oil samples with CaCl 2 and MgCl 2 concentrations below 50 mg kg−1 determined using the potentiometric method were comparable to those determined by standard methods. The TAN of crude oil samples with high salt concentrations (>500 mg kg−1) obtained by the standard methods were 77 %–90 % higher than those determined by NMS_TAN. The potentiometric method is fast, simple, and accurate and allows for robust quantifications of the TAN of different crude oil samples without chloride salt interferences. [ABSTRACT FROM AUTHOR]

2-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (MTP) was synthesized, self-assembled on the surface of gold (Au) electrode (Au-MTP) followed by characterization using Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS). CV and EIS confirmed the formation of well-organized Au-MTP SAM free from defects and pinholes. Au-MTP was further utilized as a platform for sensing of Hg2+ using EIS. The results showed sensitive and selective response of Au-MTP towards Hg2+ in the linear concentration range from 1.0 × 10−10 M to 1.0 × 10−4 M with limit of detection (LoD) of 5.6 × 10−11 M. Furthermore, MTP was self-assembled on gold nanoparticles (AuNPs) and MTP bound gold nanoparticles (MTP-AuNPs) so obtained were used as modifier for construction of carbon paste electrode (CPE). Hg2+-CPE exhibited Nernstian response towards Hg2+ with slope of 28.3 mV/decade in the concentration range from 1.0 × 10−5 M to 1.0 × 10−1 M with LoD of 6.3 × 10−6 M. Both the Au-MTP EIS sensor and Hg2+-CPE were successfully applied for estimation of Hg2+ content in tap water samples. [Display omitted] • A chelating Schiff base thiol (MTP) was synthesized and characterized. • Au-MTP SAM was characterized using CV and EIS. • Au-MTP showed EIS response towards Hg2+ with LoD 5.6 × 10−11 M. • Hg2+-CPE showed Nernstian response of 28.3 mV/decade with LoD 6.3 × 10−6 M. • Both EIS sensor and CPE were applied for determination of Hg2+ in tap water. [ABSTRACT FROM AUTHOR]

• Iodometric titration measures the highest hydroperoxide concentrations range (10−4–101 mol/L). • Potentiometry decreases the detection limit by two orders of magnitude compared to colorimetry. • Absorption measures have the lowest detection limits and can be calibrated with good accuracy. • A new method combining HPLC, a post-column reactor (PcR) and UV–vis spectrometery is proposed. • HPLC-PcR has the largest detection range (10−10–10−3 mol/L) and can be calibrated. Hydroperoxides are major products in the autoxidation of fuels and play a central role in oxidation kinetics. Their presence affects the oxidation rate, even at low concentrations, and, in turn, the thermal stability of fuels. Standard techniques for the quantification of hydroperoxides (ROOH) in fuels involve the reduction of ROOH by I−, yielding iodine (I 2), which can be quantified by titration. The ASTM titration method of ROOH is known to be poorly reproducible and have inadequate lower detection limits and limited dynamic ranges. In this work, several analytical methods for the quantification of hydroperoxides in fuels have been systematically compared for known concentrations of ROOH: titrations of iodine with thiosulfate (ASTM D3703) and triphenylphosphine (TPP) solutions, with colorimetric and potentiometric methods, and quantification of iodine by UV–visible absorption. n -decane was used as a surrogate fuel and tert -butyl hydroperoxide as the ROOH internal standard. Our systematic study shows that the ASTM method based on colorimetric titration using thiosulfate aqueous solution is the least accurate because of the non-miscibility of water and n- decane, which even makes the UV–visible spectroscopy method ineffective. The other titration method proposed in the literature, using TPP dissolved in n- decane as the titrant, does not have this miscibility problem. Potentiometric titration is found to be more reproducible and accurate than colorimetric titration. The UV–visible absorption reaches lower detection limits. We show that the combination of the potentiometric titration of iodine with TPP and UV–visible absorption enables ROOH concentrations to be determined with low detection limits and a large dynamic range. The advantages of iodometry and UV-absorption detection methods have been used to develop a new analytical method based on their coupling in HPLC with a post-column reactor. [ABSTRACT FROM AUTHOR]

[Display omitted] • As versatile ligand, ibuprofen forms 0- and 1-D structures with Zn(II) and Cu(II) metal ion respectively. • Solid-state investigations, complemented with potentiometric and 1H NMR studies. • Antimicrobial activity of ibuprofen is augmented upon metal complexation. Two new, Zn(II) and Cu(II), complexes of the non-steroidal anti inflammatory drug (NSAID) ibuprofen (HIbu) are reported. Results from their solid state investigation are complemented by potentiometric and 1H NMR studies in view of the role that chelation of these biologically relevant metal ions might play in affecting the Active Pharmaceutical Ingredient (API) biological properties, but also of the use of metallo-ibuprofen drugs. In the solid state, the ibuprofenate anion (Ibu−) gives rise to 0- and 1-D species, [Zn(Ibu) 2 (H 2 O) 2 ] and [Cu(Ibu) 2 ] n , respectively. The [Zn(Ibu) 2 ] species is also present in H 2 O/EtOH 50 % v/v solution (pK w = 14.41(1)) and starting from pH 4–4.5 coexists in solution with the [Zn(Ibu)]+ one. As for the copper structure, it represents, to the best of our knowledge, the first example of 1-D coordination polymer consisting of copper-ibuprofen dinuclear paddle-wheel units. Interestingly, this crystal phase is the only one obtained irrespective of the different synthetic and crystallization procedures adopted. Potentiometric titrations evidence that copper(II) gives the more stable complexes (also in this case [Cu(Ibu) 2 ] and[Cu(Ibu)]+ coexist in solution) with respect to the zinc ones. Lastly, in light of the increasing interest around the antibacterial activities of NSAIDs and NSAIDs-containing compounds, the antimicrobial effects of ibuprofen, [Zn(Ibu) 2 (H 2 O) 2 ] and [Cu(Ibu) 2 ] n were preliminary evaluateted on Bacillus Subtilis , chosen as a model of Gram-positive bacteria. [ABSTRACT FROM AUTHOR]

Ion-selective electrodes have become the largest and most widely utilized category of electrochemical sensors since the end of the last century, marked by the introduction of solid-contact electrodes. Ongoing research in potentiometric sensors predominantly focuses on innovating new variations or emerging trends of solid contact to yield devices with improved analytical parameters. Many advanced ion selective electrodes (ISEs) have proven to be highly effective in pharmaceutical practical applications. The inherent advantages of ISEs, including their simplicity, affordability, rapid analysis, precision and accuracy, on-site monitoring, acceptable limit of detection (LOD), wide linear range, and selectivity, make them promising candidates for pharmaceutical analysis. While numerous review articles have been published in recent years, addressing topics such as membrane materials, ionophores, functional materials, and applications in various fields, there seems to be a gap in the literature when it comes to a comprehensive review summarizing the extensive utilization of various solid-contact ion-selective electrodes (SC-ISEs) in pharmaceuticals and biomedical applications, based on our current knowledge. Therefore, this review article aims to fill this gap by focusing on advancements made in the past six years in the detection capabilities of SC-ISEs within pharmaceuticals. This review article provides an overview of the traditional and modified various types of SC-ISC viz carbonaceous, metal/metal oxide, composite based, and polymer-based ISE used for pharmaceutical analysis with their detection limit, stability, recovery, and target matrix sensing. Introduction of new materials viz. MXene and other polymeric materials give new dimensions in the future to enhance the selectivity and sensitivity of ISEs. Sensors developed with ISE have extraordinary potential to reduce the LOD of different surface modifications down to the pM level. They have the ability to perform analyses directly on the sample without requiring pretreatment in diagnostic laboratories. The intent is to provide an up-to-date and thorough overview of the progress made in the development of these electrodes, enhancing performance and accessibility in this specific area of research. [ABSTRACT FROM AUTHOR]

Fe(II)EDTA can remove NO efficiently, but it has not been industrially applied. This is because the oxygen present in the flue gas will oxidize Fe(II)EDTA and Fe(II)EDTA-NO to Fe(III)EDTA and deactivate them. In order to solve this problem, this paper innovatively proposes to use NaHS to reduce Fe(III) EDTA, because NaHS has high reducing ability and low price. Therefore, a series of experimental conditions were explored in order to obtain the best reaction setup. The results indicate that increasing the concentrations of NaHS, temperature, and pH enhances the rate of NaHS reduction. The mechanism of the increase in reduction rate was studied in depth using potentiometric titration. It was found that an increase in OH- concentration will generate S 8 precipitate, which is beneficial to the forward progress of the reaction and promotes the large-scale production of the active component Fe2+. Oxygen is an inevitable factor in actual flue gas, so this study innovatively proposed a kinetic model under aerobic conditions and used this model to predict the trend of Fe(III)EDTA reduction by NaHS. On this basis, NO removal experiments were conducted under high oxygen conditions. After 15 cycles, the reduction performance of NaHS was still very high, and the NO removal rate was higher than 70%. The reason for this phenomenon is that the stabilizer exists in a form that is conducive to the removal of NO by the active component Fe2+. Therefore, this study provides theoretical guidance for promoting the industrial application of Fe(II) EDTA technology for NO removal. [Display omitted] • The mechanism of reduction of Fe (III)EDTA by NaHS was determined. • The reaction order of NaHS reduction reaction for Fe(III)EDTA is 2. • The derived kinetic model in an aerobic environment was utilized to predict the trend of Fe(III)EDTA reduction by NaHS and validated experimentally. • NaHS has excellent cycling performance in high oxygen cycling NO removal experiments. [ABSTRACT FROM AUTHOR]

Cuttlefish bone biowaste is a potential source of a composite matrix based on chitin and aragonite. In the present work, we propose for the first time the elaboration of biocomposites based on chitosan and aragonite through the valorization of bone waste. The composition of the ventral and dorsal surfaces of bone is well studied by ICP-OES. An extraction process has been applied to the dorsal surface to extract β-chitin and chitosan with controlled physico-chemical characteristics. In parallel, aragonite isolation was carried out on the ventral side. The freeze-drying method was used to incorporate aragonite into the chitosan polymer to form CHS/ArgS biocomposites. Physicochemical characterizations were performed by FT-IR, SEM, XRD, 1H NMR, TGA/DSC, potentiometry and viscometry. The ICP-OES method was used to evaluate in vitro the bioactivity level of biocomposite in simulated human plasma (SBF), enabling analysis of the interactions between the material and SBF. The results obtained indicate that the CHS/ArgS biocomposite derived from cuttlefish bone exhibits bioactivity, and that chitosan enhances the bioactivity of aragonite. The CHS/ArgS biocomposite showed excellent ability to form an apatite layer on its surface. After three days' immersion, FTIR and SEM analyses confirmed the formation of this layer. [Display omitted] [ABSTRACT FROM AUTHOR]

• To provide some of the electrochemical biomarker mechanisms through a basic chemical level comparison. • To distinguish between current and traditional process detection methods. • To emphasize the benefits of electrochemical detection in the new era, particularly through the screen-printed electrode. In the context of biomarker mechanisms, this paper provides an overview of electrochemical energy, which is the conversion of chemical energy into electrical energy or vice versa via electrochemical processes. It also includes a comparative examination at the basic chemical level of renal function. Furthermore, it is possible to differentiate between the conventional and current systems using the process detection method. By preventing the need for severe treatments like dialysis or renal replacement therapy, new techniques for early kidney failure diagnosis can prevent additional kidney damage and, thus, lower the early detection costs associated with kidney transplantation. In this instance, the benefits of electrochemical approaches for detection and improvement have been emphasized, namely through the use of the recently developed, low-cost, small-scale Screen-Printed Electrode (SPE). [ABSTRACT FROM AUTHOR]

Reference electrodes (REs) based on moderately lipophilic ionic liquids (ILs) are an attractive approach to realize integrated potentiometric sensing systems that do not require a traditional liquid junction. However, it is not sufficiently understood how lipophilic sample ions can result in interference. Less lipophilic ILs should partition more easily into the aqueous phase where they can compete with sample ions and suppress ion-exchange, but since a decreased IL lipophilicity favors ion-exchange interference the overall effect is not immediately clear. We use here the established phase boundary potential model to describe failure of IL-based REs upon exposure to lipophilic solution ions. The traditional definition of the detection limit is employed to find the intersection of the separate Nernstian responses to IL and solution interference, which is mathematically simpler to process. The approach focuses on cation interference and considers ion pairing in the polymeric phase together with appropriate ion-exchange and coextraction equilibria. The range of RE potential stability is shown to depend on 1) the concentration of the IL in the membrane; 2) the lipophilicity of the IL expressed through its partition constant; 3) the relative lipophilicity of the lipophilic interference and the IL ion of the same charge expressed through the corresponding ion-exchange constant; 4) the stability constant of ion pairs between the interfering ion and the counterion from the IL. For the experimental evaluation of the model, two commercially available ionic liquids were selected: [C 8 mim+][C 1 C 1 N-] (IL1) and [TBMOEP+][C 1 C 1 N-] (IL2). Partition constants between water and a polymeric phase based on poly(vinyl chloride) (PVC) and dodecyl 2-nitrophenyl ether (NPDE) were determined for the first time for both IL1 (3.55 ± 0.05) and IL2 (4.68 ± 0.22) using so-called sandwich membrane experiments. Based on these values, the expected reference electrode lifetime is discussed. Tetramethylammonium, tetraethylammonium and tetrabutylammonium cations were selected as model interfering ions and the corresponding exchange constants were obtained experimentally. The model provides excellent RE failure prediction in which calculated critical activities for the tetrabutylammonium cation closely match the experimental values for both ILs. [Display omitted] • The influence of lipophilic ions on the potential of ionic liquid reference electrodes has not been fully understood before. • A model is proposed to describe the failure of reference electrodes based on ionic liquids in presence of lipophilic cations. • Partition constants in a PVC-NPDE/water system are determined for two moderately lipophilic ionic liquids. • The model provides excellent reference electrode failure prediction in terms of critical interfering ion activity. • The expected poor electrode lifetime is addressed and requirements for new ionic liquids are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cobalt oxides are synthesized via a simple co-precipitation process with different concentrations of cationic surfactant CTAB. • A low concentration of CTAB provides enhanced specific capacitance. • The symmetric supercapacitor device exhibited a specific capacitance of 296F/g at 0.8 A/g. • Asymmetric supercapacitor device offers 89% of cyclic stability with high energy density. Metal oxides are proficient electrode materials for supercapacitors because of their physiochemical properties, especially their wide range of oxidation states that facilitate charge transfer in redox reactions and compatibility with electrolytes. Their performances can be further improved by adding surfactants, which also help with controlled synthesis, inhibit aggregation, and alter surface characteristics. The functional groups present in the surfactant molecule can undergo chemical bonding with the surface of the metal oxide, thereby modifying their surface chemistry and electronic characteristics. Recent research has focused on increasing the specific capacitance of cobalt oxide owing to its large surface area and size. The surfactants help to control the surface modification as a size-reducing agent and improve the electrochemical properties. Herein, A facile co-precipitation method is employed in synthesising cobalt oxide without cationic surfactant cetyltrimethylammonium bromide (CTAB) and with different concentrations of CTAB, followed by calcination. Herein, we compare the electrochemical properties with varying concentrations of surfactant-assisted Co 3 O 4. The modified Co 3 O 4 electrode with a low surfactant concentration (CO 1) exhibits a highly specific capacitance of 531F/g at 5 mV/s with a potential window of 0.7 V. The CO 1 electrode is suitable for supercapacitor devices with a specific capacitance of 296F/g at 0.8 A/g. Moreover, the asymmetric supercapacitor composed of CO1//AC demonstrated a remarkable energy density of 46.2 Wh/Kg and a robust power density of 800 W/kg. These results indicate that the hierarchical porous structure accelerates electron and ion movement, lowers charge transfer resistance, and improves hybrid electrode capacitive properties. [ABSTRACT FROM AUTHOR]

Acrylic acid and vinylamine copolymers represent one of the simplest polyampholyte structures. The acid-base and solution properties of these copolymers are hardly studied, and there are no works devoted to the synthesis of a set of copolymers with different compositions. We have synthesized a set of acrylic acid and vinylamine copolymers containing from 21 to 95 mol% acrylic acid units. The copolymers show the hydrodynamic properties and solubility of typical polyampholytes. Potentiometric titration revealed unusual acid-base properties of the new copolymers. The addition of HCl to the copolymers in the form of sodium/potassium salt results in only partial protonation of carboxyl anions and amine groups, including the acidic range (pH 2.5). This abnormally high acidity of acrylic acid and vinylamine copolymers is probably due to the formation of strong intra- and intermolecular hydrogen or ionic bonds between partially protonated and protonated groups: ∼COO−+H 3 N∼, COOH∙∙∙:NH 2 ∼, ∼H 2 N:∙∙∙ +H 3 N∼. Poly(vinylamine) and copolymers are able to stabilize curcumin in aqueous medium, significantly increasing its concentration in the neutral pH range. Polymers with high content of amine groups prevent curcumin degradation, probably by converting it to a more stable anionic form. New copolymers are promising substances for the creation of nucleic acid carriers for gene therapy and genetic engineering. The copolymer containing 21 % acrylic acid is comparable to poly(vinylamine) in terms of interaction with oligonucleotides, but yields more homogeneous polyplexes without the impurity of positively charged and potentially toxic particles. [Display omitted] • Co(acrylic acid – vinylamine) containing 21–95 mol% acrylic acid units were obtained. • The copolymers showed abnormally high acidity due to intra-/intermolecular bonding. • The copolymers are promising substances as curcumin and nucleic acid carriers. [ABSTRACT FROM AUTHOR]

Defining the distribution of the chemical species in a multicomponent system is a task of great importance with applications in many fields. To clarify the identity and the abundance of the species that can be formed by the interaction of the components of a solution, it is fundamental to know the formation constants of those species. The determination of equilibrium constants is mainly performed through the analysis of experimental data obtained by different instrumental techniques. Among them, potentiometry is the elective technique for this purpose. As such, a survey was run within the NECTAR COST Action – Network for Equilibria and Chemical Thermodynamics Advanced Research, to identify the most used software for the analysis of potentiometric data and to highlight their strengths and weaknesses. The features and the calculation processes of each software were analyzed and rationalized, and a simulated titration dataset of a hypothetic hexaprotic acid was processed by each software to compare and discuss the optimized protonation constants. Moreover, further data analysis was also carried out on the original dataset including some systematic errors from different sources, as some calibration parameters, the total analytical concentration of reagents and ionic strength variations during titrations, to evaluate their impact on the refined parameters. Results showed that differences on the protonation constants estimated by the tested software are not significant, while some of the considered systematic errors affect results. Overall, it emerged that software commonly used suffer from many limitations, highlighting the urgency of new dedicated and modern tools. In this context, some guidelines for data generation and treatment are also given. [Display omitted] • Five software used to optimize log K from potentiometric data are critically evaluated. • A simulated titration dataset of a hexaprotic acid was processed by five software. • The impact on log K of systematic errors occurring during titrations is evaluated. • The impact on log K of ionic strength variations occurring during titrations is evaluated. • Guidelines for data acquisition and treatment are given. [ABSTRACT FROM AUTHOR]

Flexible paper-based conducting molecularly imprinted polymer as electrochemically assisted solid phase microextraction and selective for determination of naproxen. [Display omitted] • Electrochemically prepared paper-based conducting molecularly imprinted polymer film. • Flexible paper-based film applied in naproxen selective sorbent and sensor devices. • Fabricated analytical devices were used for drug determination in human serum sample. • These devices have potential to be used in lab on a chip system and wearable sensors. An electrochemical method is presented for the preparation of paper-based conductive molecular imprinted polymer (CMIP) film as a recognition element of a sensor and a selective absorber in separation methods. The paper became conductive by chemically incorporating polypyrrole (PPy) doped with anion dopant. The effects of the anion dopant and oxidant type on the conductivity of the modified paper were studied. Afterward, a CMIP film based on PPy and an anionic drug as a template was electrochemically synthesized on conductive paper surface, which was then utilized as a selective sorbent for electrochemically assisted solid phase microextraction (EC-SPME) and a recognition element in fabricating flexible drug-selective sensor. Factors affecting the performance of the paper-based EC-SPME device were studied in naproxen (NAP) analysis. All quantitative analytical parameters in the EC-SPME device were obtained by UV–vis absorption spectroscopy. Under the optimal conditions, linearity was achieved within the range of 2.0 × 10−7–2.0 × 10−5 mol/L with determination coefficient (R2 = 0.99) and the limit of detection (LOD) was 0.6 × 10−7mol/L. Moreover, a fabricated paper-based NAP-selective sensor, showed Nernstian response slopes of −61.6 ± 0.5 mV decade−1 over the linear range of 4.0 × 10−7–1.0 × 10−2 mol/L and LOD was 2.0 × 10−7 mol/L. The applicability and efficiency of the paper-based analytical devices were investigated for NAP determination as a model drug in human serum samples. The recoveries were obtained in the range of 90.0–103.0 %. Accordingly, paper-based CMIPs were found to be a novel fabrication method for efficient, selective, flexible and cost-effective material for analytical devices. [ABSTRACT FROM AUTHOR]

A novel method of determining indium has been described in this article which uses adsorptive stripping voltammetry (AdSV) and 4-(2-pyridylazo)-resorcinol (PAR) as a chelating agent or as the preconcentration agent. The measurements were performed using square-wave voltammetry by using a combined electrode system, which allows for preconcentration and stripping without opening the circuit. Ex situ plated bismuth film electrode (BiFE) was used as the working electrode. A potential-time program was developed for the inversion cycle stages based on the various factors that affect the magnitude of the inversion signal. The calibration curve was linear in a concentration range of 2·10−7 to 4·10−6 М when the pH is 4.8, accumulation potential is −700 mV, and PAR concentration is 1·10−4 M. The detection limit for the 3σ criterion with an accumulation time of 120 s was 3.5·10−9 М. Several interferences caused by Tl(I), Zn(II), Cu(II), Pb(II), Co(II), Ni(II), Mn(II), Fe(III), Cr(III) ions have been studied, and it has been shown that medium exchange procedure can effectively eliminate some interferences. It was demonstrated that the method can be applied to the determination of indium in tap water and in ITO glass sample. [Display omitted] • Adsorptive stripping voltammetry of In(III) performed with Bismuth Film Electrode. • Determination of In(III) based on its complexation with 4-(2-pyridylazo)-resorcinol. • Electrolyte solution automatically replaced using a three-in-one combined electrode. • Electrolyte replacement at the stripping step gave high sensitivity/selectivity. • Method provided high accuracy for In(III) detection in tap water and ITO glass. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesized OPHS zwitterionic surfactant exhibits wetting reversal and competitive adsorption effects. • The wetting reversal mechanism of OPHS has a time-dependent effect. • OPHS can remove the adsorbed oil film on the shale surface and desorb methane. • Contact angle testing proved effective wettability alteration by OPHS zwitterionic surfactant. Shale reservoirs have the characteristics of low permeability and low porosity. In order to enhance the recovery of shale oil and gas, surfactant flooding is a mature reservoir oil recovery method. However, the adsorption of different surfactants on the reservoir rock surface is restricted, depending on the type of surfactant. Therefore, a zwitterionic surfactant (OPHS) was synthesized from oleic acid, 3-dimethylaminopropylamine and sodium 3-chloro-2hydroxypropanesulfonate, and characterized by FTIR, 1H NMR, and TGA, and the mechanism of the OPHS for enhancing oil and gas recovery on shale surfaces was investigated. The results showed that the critical micelle concentration (CMC) of OPHS surfactant solution is 7.9 × 10-4 mol/L and the γ CMC is 27.5 mN/m; the concentration of 0.1 % OPHS surfactant solution could reduce the contact angle of the cores from 127.2° to 38.8°, which resulted in spontaneous imbibition; The absolute Zeta potential of shale particles in the OPHS surfactant solution was measured at 39 mV, whereas in deionized water at 15.3 mV. This difference can be attributed to the formation of a stable hydration film on the surface of shale particles induced by the wetting reversal effect. Spontaneous imbibition experiments showed that a 0.1 % solution of OPHS surfactant was able to increase the recovery rate by more than four times compared to the imbibition solution without added surfactant; In high-pressure gas adsorption/desorption experiments, the OPHS surfactant solution demonstrated a higher affinity for adsorption onto the shale surface. It effectively occupied adsorption sites, ultimately facilitating methane gas desorption from the shale. In summary, OPHS zwitterionic surfactants exhibit the capability to desorb hydrocarbons from shale pores through mechanisms such as wetting reversal and competitive adsorption. This research holds significant potential for advancing the field of shale oil and gas recovery, providing valuable insights for enhancing recovery processes. [ABSTRACT FROM AUTHOR]

This paper presents the results of studying the acid-base properties of the indicator dye methyl yellow in water–ethanol solutions with a volume fraction of alcohol of 10 % and 50 %. The influence of the addition of NaCl salts and tetrabutylammonium chloride, as well as the anionic surfactant sodium dodecylsulfate (SDS) on the acidity constant of the indicator, was evaluated. Under the chosen conditions, ethanol additives have a more significant effect on the p K a value. For the first time, using the dynamic light scattering method, the particle sizes, polydispersity index, and ζ-potential of colloidal particles in pure aqueous and mixed water–ethanol solutions of methyl yellow (φ alcohol from 0.2 % to 50 %) in the presence of NaCl and SDS were estimated. In solutions with φ alcohol = 50 % colloidal particles were not found. It has been shown that the hardened gelatin gel of photographic film can be used as a convenient sorbent for methyl yellow. In the process of dye extraction into a gelatin film from water-alcohol solutions containing SDS and NaCl, the acid-base properties of the methyl yellow remained almost unchanged. The difference between the p K a values obtained for the indicator both in solution and in the film did not exceed the measurement error. [ABSTRACT FROM AUTHOR]

The multi-ionic adsorption behavior of recycled cement paste (RCP) exposed to NaCl and CaCl 2 solutions is investigated in this study by comparing with that of the ordinary cement paste (OCP). The adsorption of Na+, K+, Ca2+, and Cl- in RCP and OCP are quantified by ICP-OES and potentiometric titration. RCP has larger adsorption capacity for Na+, K+, and Cl- compared to OCP, which is attributed to a lager specific surface area of RCP. For the multi-ion adsorption of OCP and RCP in both NaCl and CaCl 2 solutions, the adsorption amount of minor cation ions are found to be influenced by the concentration of primary cation ion, reflecting a competitive adsorption among cation ions. Besides, the maximum Na+ adsorption amount is proportional to the product of the specific surface area and the percentage of the silanol groups in CSH measured by 29Si NMR spectroscopy. Additionally, molecular dynamics simulation is conducted to investigate the Na+ and Cl- adsorption behavior of CSH in OCP and RCP at a molecular level. The simulation results confirm the higher adsorption capacity of OCP than RCP. • The multi-ionic adsorption behavior of RCP-exposed to chloride solutions by comparing with that of OCP was investigated. • A competitive adsorption among cation ions was found for the multi-ions adsorption of OCP and RCP in chloride solutions. • The maximum adsorption of Na+ is proportional to the product of specific surface area and percentage of silanol groups. [ABSTRACT FROM AUTHOR]

We report here on the development of thin-layer ion-selective membranes containing lipophilic TEMPO as a phase-transfer redox mediator for the simultaneous detection of non-redoxactive ions. This redox probe was recently introduced by our group and provides ideal ion-transfer waves when the membrane is interrogated by cyclic voltammetry. To perform multianalyte detection in the same sensing film, plasticized PVC-based membranes were doped with lithium and potassium ionophores in addition to a lipophilic cation-exchanger. The ionophores allow for ion discrimination owing to the different ionophore-cation complexation constants and the oxidation of TEMPO to the oxoammonium form results in the selective transfer of lithium and potassium at different potentials. The resulting voltammograms have half-peak widths of 100 and 102 mV, and the peak separation between anodic and cathodic scans is 8 and 9 mV for lithium and potassium, respectively, close to theoretical expectations. High peak resolution was observed, and the ion-transfer waves are still distinguishable when the ion activities differ by three orders of magnitude. These parameters are remarkably better than those obtained with other redox probes, which is important for multianalyte detection in the same voltammetric scan. Optimized membranes showed independent Nernstian shifts (slopes of 59.23 mV and 54.8 mV for K+ and Li+, respectively) of the peak position for increasing ion concentrations. An idealized model for two ionophore-based membranes combining redox and phase-boundary potentials was applied to the proposed system with excellent correlation. Potassium and lithium ions were simultaneously detected in undiluted human serum samples with good accuracy and precision. [Display omitted] • TEMPO opens new horizons as a redox probe for producing reversible multianalyte sensors. • Ion transfer by cyclic voltammetry provides ideal peak shapes for multi-ion sensing in a single voltammogram. • Thin layer membranes containing multiple ionophores allow for excellent ion discrimination. • Well-resolved ion-transfer waves have independent Nernstian behavior in agreement with an idealized model. [ABSTRACT FROM AUTHOR]

Solid-contact polymeric membrane ion-selective electrodes (ISEs) have been an attractive tool for potentiometric sensors. Sufficient transducing performance evaluation and multiple potentiometric analysis are critical to evaluate whether the solid contact transducer material used in ISE is promising. Herein, we describe sandwich-like MXene/MWCNTs-based polymeric membrane ISEs with three-readout strategies of potential response, chronopotentiometric response, and transition time response. The MXene/MWCNTs can be readily prepared by the electrostatic self-assembly strategy, which not only prevented the aggregation of MXene nanosheets and facilitated charge-transfer, but also significantly contributed to the large double-layer capacitance and water-layer free from interference. With Ca2+ as a model, two kinds of Ca2+-ISEs based on thermodynamic response and dynamic response by modulating the polymeric membrane components with three readouts were explored. Moreover, the proposed Ca2+-ISEs under different background electrolytes exhibit the similar Nernstian responses in potentiometry, variable super-Nernstian ranges in chronopotentiometry, and the consistent transition time readout. This study offers a facile MXene/MWCNTs transducer to develop a highly reliable polymeric membrane ISE. [Display omitted] • Sandwich-like MXene/MWCNTs composite is used as a solid contact. • The solid contact contributes to large double-layer capacitance and water-free layer interference. • Three analytical signals of potentiometry, chronopotentiometry and transition time are proposed. • The solid contact is feasible for thermodynamic as well as dynamic potentiometiomeric response. [ABSTRACT FROM AUTHOR]

Here, we explicitly define a half-cell reaction approach for pH calculation using the electrode couple comprised of the solid-state chloride ion-selective electrode (Cl-ISE) as the reference electrode and the hydrogen ion-selective ion-sensitive field effect transistor (ISFET) of the Honeywell Durafet as the hydrogen ion H + -sensitive measuring or working electrode. This new approach splits and isolates the independent responses of the Cl-ISE to the chloride ion Cl − (and salinity) and the ISFET to H + (and pH), and calculates pH directly on the total scale pH total EXT in molinity (mol (kg-soln)−1) concentration units. We further apply and compare pH total EXT calculated using the half-cell and the existing complete cell reaction (defined by Martz et al. (2010)) approaches using measurements from two SeapHOx sensors deployed in a test tank. Salinity (on the Practical Salinity Scale) and pH oscillated between 1 and 31 and 6.9 and 8.1, respectively, over a six-day period. In contrast to established Sensor Best Practices, we employ a new calibration method where the calibration of raw pH sensor timeseries are split out as needed according to salinity. When doing this, pH total EXT had root-mean squared errors ranging between ±0.0026 and ±0.0168 pH calculated using both reaction approaches relative to pH total of the discrete bottle samples pH total disc. Our results further demonstrate the rapid response of the Cl-ISE reference to variable salinity with changes up to ±12 (30 min)−1. Final calculated pH total EXT were ≤±0.012 pH when compared to pH total disc following salinity dilution or concentration. These results are notably in contrast to those of the few in situ field deployments over similar environmental conditions that demonstrated pH total EXT calculated using the Cl-ISE as the reference electrode had larger uncertainty in nearshore waters. Therefore, additional work beyond the correction of variable temperature and salinity conditions in pH calculation using the Cl-ISE is needed to examine the effects of other external stimuli on in situ electrode response. Furthermore, whereas past work has focused on in situ reference electrode response, greater scrutiny of the ISFET as the H + -sensitive measuring electrode for pH measurement in natural waters is also needed. • Electrode responses are split out and isolated using half reactions. • A new approach for pH calculation using half reactions is explicitly defined. • pH calculation uses single ion activity coefficients for the chloride and hydrogen ions. • This new pH calculation approach is optimized for salinities between 0.105 and 35. • pH can now be calculated directly on the total scale in molinity (mol (kg soln)−1). [ABSTRACT FROM AUTHOR]

Thiosemicarbazone derivative molecules have proven to be good sensor materials in studies using various analytical methods. In this study, new ion–selective sensors were prepared using 2–furaldehyde thiosemicarbazone and their potentiometric properties were then tested. The newly developed copper(II)–selective sensors were successfully applied for the determination of copper(II) ion content in various environmental samples with very good performance. The data obtained with the developed sensor were compared with atomic absorption spectroscopy and it was determined that the results of both methods were compatible with each other. [Display omitted] Thiosemicarbazone derivative molecules have proven to be good sensor materials in studies using various analytical methods. In this study, new ion–selective sensors were prepared using 2–furaldehyde thiosemicarbazone and their potentiometric properties were then tested. The prepared sensors exhibited a very good selectivity towards copper(II) ions over various ions. Surface images and mappings of the prepared sensors were examined by scanning electron microscopy. Copper(II)–selective sensors had a Nernstian response of 28.5 ± 1.5 mV/decade, and a low detection limit of 6.89 × 10-6 mol L-1 over a wide concentration range of 1.0 × 10-5–1.0 × 10-1 mol L-1 (R 2 = 0.9992). The newly prepared copper(II)–selective sensors were shown to be produced reproducibly, stable and economically. The sensors, which can operate in a wide pH range of 5.0–9.0 without being affected by pH changes, had a fast response time of 5 s. The newly developed copper(II)–selective sensors were used as indicator electrodes for the potentiometric titration of copper(II) ions with ethylenediaminetetraacetic acid and were successfully applied for the determination of copper(II) ion content in various environmental samples with very good performance. The data obtained with the developed sensor were compared with atomic absorption spectroscopy and it was determined that the results of both methods were compatible with each other. [ABSTRACT FROM AUTHOR]

• An overview of the potentiometric biosensors to determine urea in clinical samples. • Potentiometric urea biosensors were developed with various materials, methodologies. • We investigated and compared the performance characteristics of these biosensors. Excess nitrogen in the body is converted to urea in the liver, and urea is disposed as a waste product in urine. Urea concentration can change in body fluids such as blood due to the presence of certain disorders. Therefore, the determination of urea is of high importance in various areas including medical diagnosis, as well as food quality control and environmental monitoring. Potentiometric sensors have certain advantages over their alternatives, such as rapidity, portability, cost effectiveness, high sensitivity, easy operation and simple apparatus. Potentiometric urea biosensors based on enzyme urease have been developed using various materials including nanoparticles and films, and also using different methodologies. In this review, we covered potentiometric urea biosensors reported in the literature, and touched upon their certain structure characteristics and performance parameters including detection limit, working concentration range, response time and lifetime, all of which are of practical importance. Each potentiometric urea biosensor has its own advantages and drawbacks, thus the selection of appropriate method depends on the sample to be analyzed, its urea concentration range and other requirements of the particular application. Further research is needed in order to optimize the performance of these devices and to broaden their applicability. [ABSTRACT FROM AUTHOR]