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Faradaic‐mode organic electrochemical transistors (OECT) are promising but usually need hundreds of millivolts to sustain redox reactions. Decrease or even removal of the voltage penalty is highly desirable. Herein, the Faradic regime of the OECT is broadened toward zero bias by integrating a p‐n heterojunction of Cu2S‐diethylenetriamine (DETA)‐CdS for efficient photogating of poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonate) channel. Upon light illumination, it is found that an obvious Faradaic process is evolved at the gate/electrolyte interface under zero gate bias, suggesting the potential of sensitive amperometric biodetection with enhanced signal resolution. At the Cu2S‐DETA‐CdS/liquid interface, a biosensing process is introduced, combining with a DNA walker and enzymatic biocatalytic precipitation to produce a target‐dependent diffusion barrier, modulating the amperometric output with enhanced signal variations under light irradiation compared to that in the dark. The proposed system achieves the desired analytical performance for representative target miRNA‐10b with a low detection limit of 0.21 fM. This work features a light‐mediated OECT device with enhanced signal resolution and provides new operational paradigms and insights for novel optoelectronics interfacing with biological systems. [ABSTRACT FROM AUTHOR]

The development of sensitive and selective analytical devices for monitoring glucose levels (GLU) in biological fluids is extremely important for clinical diagnostics. In this work, we produced a new composite based on NiFe2O4 and multi-walled carbon nanotubes (MWCNT), called NiFe2O4@MWCNT, to be applied as a non-enzymatic amperometric sensor for GLU. Both NiFe2O4 and NiFe2O4@MWCNT composites were properly characterized by XRD, SEM, FTIR, and Raman spectroscopy, which confirmed that the composite was successfully prepared. A glassy-carbon electrode (GCE) modified with NiFe2O4@MWCNT was investigated by cyclic voltammetry and applied for the amperometric GLU detection using batch-injection analysis (BIA). A linear working range between 50 and 600 µmol L−1 GLU with a significant increase in sensitivity (3-fold) in comparison with MWCNT/GCE was verified, with a detection limit of 36 µmol L−1. Inter-electrode measurements (n = 4, RSD = 10%) indicated that the sensor fabrication is reproducible. Furthermore, the proposed non-enzymatic sensor was selective even in the presence of other biomarkers found in urine. When applied to synthetic urine samples, recovery levels between 84 and 95% confirmed analytical accuracy and the absence of sample matrix effect. Importantly, the developed approach is simple (free of biological modifiers), fast (77 injections per hour), and practical (high-performance tool), which are suitable features for routine analyses. [ABSTRACT FROM AUTHOR]

The development of sensitive and selective analytical devices for monitoring glucose levels (GLU) in biological fluids is extremely important for clinical diagnostics. In this work, we produced a new composite based on NiFe2O4 and multi-walled carbon nanotubes (MWCNT), called NiFe2O4@MWCNT, to be applied as a non-enzymatic amperometric sensor for GLU. Both NiFe2O4 and NiFe2O4@MWCNT composites were properly characterized by XRD, SEM, FTIR, and Raman spectroscopy, which confirmed that the composite was successfully prepared. A glassy-carbon electrode (GCE) modified with NiFe2O4@MWCNT was investigated by cyclic voltammetry and applied for the amperometric GLU detection using batch-injection analysis (BIA). A linear working range between 50 and 600 µmol L−1 GLU with a significant increase in sensitivity (3-fold) in comparison with MWCNT/GCE was verified, with a detection limit of 36 µmol L−1. Inter-electrode measurements (n = 4, RSD = 10%) indicated that the sensor fabrication is reproducible. Furthermore, the proposed non-enzymatic sensor was selective even in the presence of other biomarkers found in urine. When applied to synthetic urine samples, recovery levels between 84 and 95% confirmed analytical accuracy and the absence of sample matrix effect. Importantly, the developed approach is simple (free of biological modifiers), fast (77 injections per hour), and practical (high-performance tool), which are suitable features for routine analyses.

Developing a noninvasive skin peroxide monitoring technology is highly desirable for managing a number of metabolic disorders associated with diabetes, pulmonary diseases, or other health conditions. To date, the majority of studies on peroxide detection have been conducted on simulated sweat and high pH conditions, which are beyond the physiological range, in order to provide an enhanced response. Here, a skin-worn amperometric sensor, based on laser-induced graphene (LIG), surface-engineered with a Prussian blue (PB)–chitosan (CS) network was fabricated by one-step electrodeposition for the stable and sensitive detection of H2O2 in human eccrine perspiration. The hybrid (PB–CS) network and laser-written electrode configuration were optimized through systematic investigation of electrodeposition parameters and concurrent feedback from electrochemical and morphological characterization at each fabrication step. Different from the multitude of carbon-based electrodes functionalized with metallic nanoparticles reported in the literature, the sensor was operated at a low potential of −0.036 V vs Ag/AgCl in unmodified human eccrine perspiration. The low working potential ensured that the sensor is highly specific, immune to the current from oxygen reduction or common interfering species, whereas the inclusion of CS in the hybrid coating afforded a highly stable performance over a period of 14 days. The sensor was able to monitor H2O2 over the linear range of 10–1000 μM with a low detection limit of 6.31 μM and achieved a recovery of 98.73% (%RSD 0.86) in human eccrine perspiration. This facile biosensor based on directly laser-written electrodes coupled with the one-step PB–CS fabrication strategy has the potential to form the basis for the development of oxidase enzyme-based sensors in sweat. [ABSTRACT FROM AUTHOR]

The standard method to determine chemical oxygen demand (COD) with K2Cr2O6 uses harmful chemicals, has a long analysis time, and cannot be used for on-site online monitoring. It is therefore necessary to find a fast, cheap, and harmless alternative. The amperometric determination of COD on boron-doped diamond (BDD) electrodes is a promising approach. However, to be a suitable alternative, the electrochemical method must at least be able to determine the COD of water samples independently of the contained substances. Therefore, the current signal as a function of various organic materials was investigated for the first time. It was shown that the height of the signal current depended on the type of organic matter in single-substance solutions and that this substance dependency increases with the amount of COD. Those findings could be explained by the mechanism proposed for this reaction, showing that the selectivity of the reaction depends on the ratio of the concentration of hydroxyl radicals and organic species. We give an outlook on how to improve the method in order to increase the linear working range and avoid signal variance and how to further explain the signal variance. [ABSTRACT FROM AUTHOR]

Sulfite determination in foods and alcoholic beverages is a common requirement by food and drug administration organisations in most countries. In this study, the enzyme, sulfite oxidase (SOx), is used to biofunctionalise a platinum-nanoparticle-modified polypyrrole nanowire array (PPyNWA) for the ultrasensitive amperometric detection of sulfite. A dual-step anodisation method was used to prepare the anodic aluminum oxide membrane used as a template for the initial fabrication of the PPyNWA. PtNPs were subsequently deposited on the PPyNWA by potential cycling in a platinum solution. The resulting PPyNWA-PtNP electrode was then biofuntionalised by adsorption of SOx onto the surface. The confirmation of the adsorption of SOx and the presence of PtNPs in the PPyNWA-PtNPs-SOx biosensor was verified by scanning electron microscopy and electron dispersive X-ray spectroscopy. Cyclic voltammetry and amperometric measurements were used to investigate the properties of the nanobiosensor and to optimise its use for sulfite detection. Ultrasensitive detection of sulfite with the PPyNWA-PtNPs-SOx nanobiosensor was accomplished by use of 0.3 M pyrrole, 10 U mL−1 of SOx, adsorption time of 8 h, a polymerisation period of 900 s, and an applied current density of 0.7 mA cm−2. The response time of the nanobiosensor was 2 s, and its excellent analytical performance was substantiated with a sensitivity of 57.33 μA cm−2 mM−1, a limit of detection of 12.35 nM, and a linear response range from 0.12 to 1200 μM. Application of the nanobiosensor to sulfite determination in beer and wine samples was achieved with a recovery efficiency of 97–103%. [ABSTRACT FROM AUTHOR]

The synthesis of ultrasmall Ta2O5 nanoparticle anchored Pt atom using aspartic acid-functionalized graphene quantum dot (Asp-GQD) is reported. The Asp-GQD was combined with tantalic acid and chloroplatinic acid to rapidly form water-soluble Ta-Asp-GQD and Pt-Asp-GQD complex. Followed by thermal annealing at 900 °C in N2 to obtain Ta2O5-Asp-GQD-Pt. The study shows that the introduction of Asp-GQD as a chelating agent and p-type semiconductor achieves to the formation of ultrasmall Ta2O5 nanoparticle, PN junction at the interface and Pt single atom anchored on the surface of Ta2O5 nanocrystals. The unique structure realizes ultrahigh uricase activity and catalase activities of Ta2O5-Asp-GQD-Pt. The Ta2O5-Asp-GQD-Pt was used as the bifunctional sensing material for the construction of an electrochemical uric acid sensor. The differential pulse voltammetric current at 0.45 V linearly increases with the increase of uric acid concentration in the range 0.001–5.00 mM with the detection limit of 0.41 μM (S/N = 3). The sensor exhibits a much better sensitivity compared with the reported methods for the detection of uric acid. The proposed analytical method has been applied to the electrochemical detection of uric acid in human serum with a spiked recovery of 95–105%. The study also offers one way to design and synthesize multifunctional sensing materials with high catalytic activity. [ABSTRACT FROM AUTHOR]

The aim of this electrochemical study was to ascertain which type of electrochemically deposited carbonyl functionalized polymer represents the most suitable electrode substrate for direct covalent immobilization of biological catalysts (enzymes). For this purpose, a triad of amperometric biosensors differing in the type of conductive polymers (poly-vanillin, poly-trans-cinnamaldehyde, and poly-4-hydroxybenzaldehyde) and in the functioning of selected enzymes (tyrosinase and alkaline phosphatase) has been compared for the biosensing of neurotransmitters (dopamine, epinephrine, norepinephrine, and serotonin) and phenyl phosphates (p-aminophenyl phosphate and hydroquinone diphosphate). The individual layers of the polymers were electrochemically deposited onto commercially available screen-printed carbon electrodes (type C110) using repetitive potential cycling in the linear voltammetric mode. Their characterization was subsequently performed by SEM imaging and attenuated total reflectance FTIR spectroscopy. Molecules of enzymes were covalently bonded to the free carbonyl groups in polymers via the Schiff base formation, in some cases even with the use of special cross-linkers. The as-prepared biosensors have been examined using cyclic voltammetry and amperometric detection. In this way, the role of the carbonyl groups embedded in the polymeric structure was defined with respect to the efficiency of binding enzymes, and consequently, via the final (electro)analytical performance. [ABSTRACT FROM AUTHOR]

Abstract Cellulases are a group of enzymes, which catalyse different steps of cellulose hydrolysis, and are broadly used in industry as unpurified mixtures of several enzymes. The total activity of cellulase is defined as the ability of the enzyme to produce glucose, which is the final product of cellulose hydrolysis, and is expressed in cellulase units. However, common strategies for the determination of the cellulolytic activity of industrial cellulase preparations are based on the assessment of different steps of cellulose hydrolysis, and the results obtained with different methods are not similar. The aim of the present study was to develop an assay for the determination of cellulase activity that relies on the amperometric determination of the final product of cellulose hydrolysis glucose. The assay conditions were optimized using response surface methodology (RSM) combined with Box-Behnken design. The detection limit of the proposed method was 1.71 ± 0.06 U. We compared the results of the amperometric method with the ones obtained with the spectrophotometric method and viscosimetry in a commercial cellulose preparation.

Glucose detection using sensing materials has lately received interest due to the increased demand for sensitive and selective glucose sensors in pharmaceutical, clinical, and industrial settings. Carbon nanotubes (CNTs) are used intensively as a specific class of effective electrode substances in electrochemical sensing due to their large surface area and interesting physical and electrochemical characteristics. Nickel is an attractive transition metal for glucose electrooxidation with high catalytic activity. In this study, CNT/MoS2/NiNPs nanocomposites with different CNT/MoS2 ratios have been prepared by a hydrothermal reaction. The CNT/MoS2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR), and their morphology and composition were characterized by field emission scanning electron microscopy (FESEM). Electrocatalytic activity of the as-prepared nanomaterials towards glucose oxidation was investigated by cyclic voltammetry and amperometry in alkaline media. An excellent sensitivity value of 1212 μA·mM−1·cm−2 with a wide linear range (0.05–0.65 mM), a low detection threshold of 0.197 μM and a short response time (3 s) were achieved by the hybrid CNT/MoS2/NiNPs sensor. Its superior catalytic activity and low cost make this hybrid very promising for applications in the direct sensing of glucose.

Food contamination by aflatoxins is an urgent global issue due to its high level of toxicity and the difficulties in limiting the diffusion. Unfortunately, current detection techniques, which mainly use biosensing, prevent the pervasive monitoring of aflatoxins throughout the agri-food chain. In this work, we investigate, through ab initio atomistic calculations, a pyrrole-based Molecular Field Effect Transistor (MolFET) as a single-molecule sensor for the amperometric detection of aflatoxins. In particular, we theoretically explain the gate-tuned current modulation from a chemical–physical perspective, and we support our insights through simulations. In addition, this work demonstrates that, for the case under consideration, the use of a suitable gate voltage permits a considerable enhancement in the sensor performance. The gating effect raises the current modulation due to aflatoxin from 100% to more than 10 3 ÷ 10 4 %. In particular, the current is diminished by two orders of magnitude from the μA range to the nA range due to the presence of aflatoxin B1. Our work motivates future research efforts in miniaturized FET electrical detection for future pervasive electrical measurement of aflatoxins. [ABSTRACT FROM AUTHOR]

An alkaline mixture containing copper(II) spices, graphene oxide and glucose was heated by far infrared radiations to synthesize graphene‐cuprous oxide hybrid. The hybrid was blended with mineral oil and packed into tubes to fabricate paste electrodes. The electrodes were coupled with capillary electrophoresis for the detection of polyhydroxy compounds. The sensitivities of them on the hybrid electrodes were significantly enhanced by taking advantages of graphene and cuprous oxide. The contents of polyhydroxy compounds in tobacco method was determined by the electrodes with satisfactory assay results. [ABSTRACT FROM AUTHOR]

A procedure was suggested for voltammetric determination of streptomycin from the catalytic current on a glassy carbon electrode with a composite based on reduced graphene oxide and gold–nickel binary system. The working conditions of the electrode modification (volume of the graphene oxide and chitosan suspension, duration of the electrolytic reduction of immobilized graphene oxide and electrodeposition of the gold–nickel binary system) and the conditions for recording the catalytic current in the flow injection system were determined. The procedure for streptomycin determination in a flow, compared to the determination under stationary conditions, is more sensitive, reproducible, and rapid. The streptomycin detection limit was 0.45 nmol, and the productive capacity of the analysis was 60 samples per hour. The streptomycin determination procedure passed trials in analysis of cow milk. [ABSTRACT FROM AUTHOR]

Cobalt hydroxide nanoparticles (Co(OH)2 NPs) were uniformly deposited on flexible carbon cloth substrate (Co(OH)2@CC) rapidly by a facile one-step electrodeposition, which can act as an enzyme-free glucose and uric acid sensor in an alkaline electrolyte. Compositional and morphological characterization were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), which confirmed the deposited nanospheres were Co(OH)2 nanoparticles (NPs). The electrochemical oxidation of glucose and uric acid at Co(OH)2@CC electrode was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry methods. The results revealed a remarkable electrocatalytic activity toward the single and simultaneous determination of glucose and uric acid at about 0.6 V and 0.3 V (vs. Ag/AgCl), respectively, which is attributed to a noticeable synergy effect between Co(OH)2 NPs and CC with good repeatability, satisfactory reproducibility, considerable long-term stability, superior selectivity, outstanding sensitivity, and wide linear detection range from 1 uM to 2 mM and 25 nM to 1.5 uM for glucose and UA, respectively. The detection limits were 0.36 nM for UA and 0.24 μM for glucose (S/N = 3). Finally, the Co(OH)2@CC electrode was utilized for glucose and uric acid determination in human blood samples and satisfying results were obtained. The relative standard derivations (RSDs) for glucose and UA were in the range 6 to 14% and 0 to 3%, respectively. The recovery ranges for glucose an UA were 97 to 103% and 95 and 101%, respectively. These features make the novel Co(OH)2@CC sensor developed by a low-cost, efficient, and eco-friendly preparation method a potentially practical candidate for application to biosensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • An abscisic acid receptor modified carbon fiber microelectrodes was fabricated. • The mediated reaction of Cu+ with K 3 Fe(CN) 6 realized the amplification responses. • The release of ABA from single protoplasts induced by stimulants was monitored. It was previously reported that stress induces a cellular production of abscisic acid in plants, but no direct method shows the evidence. Here, an electrochemical microsensor involving an abscisic acid receptor PYL2 modified carbon fiber microelectrode was fabricated by self-assembly method, where the Cu2+ combined with the histidine tag of PYL2 on the surface of microelectrode was used as the detection probe, the mediated reaction between Cu+ and ferricyanide realized the amplification responses and provided the microsensor with a high sensitivity for detection of abscisic acid with a detection limit of 0.8 nM. With use of this microsensor, an increase of extracellular abscisic acid from single rice protoplast induced by sulfate, osmotic and salinity stress was real-time monitored. Direct measurement of free extracellular abscisic acid in single plant cells might offer important new insights into its role in plants challenged by abiotic stresses. [ABSTRACT FROM AUTHOR]

Fusaric acid (FA) is a secondary fungal metabolite, which is widespread on corn and corn-based feed and food; FA has non-specific toxicity. Biosensor method is an express and easy-to-use method for quantitative and qualitative assessment of FA effect. Search for cultures has been performed for the formation of laboratory models of FA biosensor with the Clark-type oxygen electrode as transducer: respiration intensity of chosen cultures changed in the presence of FA. Resting cells of Fusarium oxysporum f. sp. vasinfectum and Bacillu s subtilis were used as receptors of the amperometric biosensor for FA determination in aqueous solution. To enhance the sensitivity of detection, induction by substrate was performed for Bacillu s subtilis. Response-concentration linear dependencies were obtained in a range of 0.5–500 FA mg/L. Biosensor models were applied to characterize influence of FA on microbial cells and investigate some features of FA transport. The dependences of the cells' response to FA on FA concentration were obtained; the kinetic parameters S 0.5 and V max were determined for each culture. Inhibition-threshold FA (Sit) concentrations were similar for both studied cultures. At concentrations lower than S it , the process of simple diffusion governed FA transport into cells and caused the cells' response to FA for non-induced culture. • Microbial cells were used for amperometric detection of fusaric acid (FA). • The range of electrochemical determination of FA was 0.5–500 mg/L. • An immobilized culture-receptor can be used to characterize the FA influence on microbes. • Inhibition-threshold FA concentration was about 550 mg/L. • The sensitivity of method was increased due to induction by substrate. [ABSTRACT FROM AUTHOR]

Cellulases are a group of enzymes, which catalyse different steps of cellulose hydrolysis, and are broadly used in industry as unpurified mixtures of several enzymes. The total activity of cellulase is defined as the ability of the enzyme to produce glucose, which is the final product of cellulose hydrolysis, and is expressed in cellulase units. However, common strategies for the determination of the cellulolytic activity of industrial cellulase preparations are based on the assessment of different steps of cellulose hydrolysis, and the results obtained with different methods are not similar. The aim of the present study was to develop an assay for the determination of cellulase activity that relies on the amperometric determination of the final product of cellulose hydrolysis glucose. The assay conditions were optimized using response surface methodology (RSM) combined with Box-Behnken design. The detection limit of the proposed method was 1.71 ± 0.06 U. We compared the results of the amperometric method with the ones obtained with the spectrophotometric method and viscosimetry in a commercial cellulose preparation. [ABSTRACT FROM AUTHOR]

A laser-induced graphene (LIG) surface modified with Prussian blue (iron hexacyanoferrate) is demonstrated as a novel electrochemical sensing platform for the sensitive and selective detection of hydrogen peroxide. Electrochemical Prussian blue (PB) modification on porous graphene films engraved by infrared laser over flexible polyimide was accomplished. Scanning electron microscopy images combined with Raman spectra confirm the formation of porous graphene and homogenous electrodeposition of PB over this porous surface. Electrochemical impedance spectroscopy reveals a substantial decrease in the resistance to charge transfer values (from 395 to 31.4 Ω) after the PB insertion, which confirms the formation of a highly conductive PB-graphene composite. The synergistic properties of PB and porous graphene were investigated for the constant monitoring of hydrogen peroxide at 0.0 V vs. Ag|AgCl|KCl(sat.), under high-flow injections (166 µL s−1) confirming the high stability of the modified surface and fast response within a wide linear range (from 1 to 200 µmol L−1). Satisfactory detection limit (0.26 µmol L−1) and selectivity verified by the analysis of complex samples confirmed the excellent sensing performance of this platform. We highlight that the outstanding sensing characteristics of the developed sensor were superior in comparison with other PB-based or LIG-based electrochemical sensors reported for hydrogen peroxide detection. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) cobalt molybdate (CoMoO4) hierarchical nanoflake arrays on pencil graphite electrode (PGE) (CoMoO4/PGE) are actualized via one-pot hydrothermal technique. The morphological features comprehend that the CoMoO4 nanoflake arrays expose the 3D, open, porous, and interconnected network architectures on PGE. The formation and growth mechanisms of CoMoO4 nanostructures on PGE are supported with different structural and morphological characterizations. The constructed CoMoO4/PGE is operated as an electrocatalytic probe in enzyme-less electrochemical glucose sensor (ELEGS), confronting the impairments of cost- and time-obsessed conventional electrode polishing and catalyst amendment progressions and obliged the employment of a non-conducting binder. The wide-opened interior and exterior architectures of CoMoO4 nanoflake arrays escalate the glucose utilization efficacy, whilst the intertwined nanoflakes and graphitic carbon layers, respectively, of CoMoO4 and PGE articulate the continual electron mobility and catalytically active channels of CoMoO4/PGE. It jointly escalates the ELEGS concerts of CoMoO4/PGE including high sensitivity (1613 μA mM−1 cm−2), wide linear glucose range (0.0003–10 mM), and low detection limit (0.12 µM) at a working potential of 0.65 V (vs. Ag/AgCl) together with the good recovery in human serum. Thus, the fabricated CoMoO4/PGE extends exclusive virtues of modest electrode production, virtuous affinity, swift response, and excellent sensitivity and selectivity, exposing innovative prospects to reconnoitring the economically viable ELEGSs with binder-free, affordable cost, and expansible 3D electrocatalytic probes. [ABSTRACT FROM AUTHOR]

A porous layer of copper was formed on the surface of screen-printed carbon electrodes via the colloidal crystal templating technique. An aqueous suspension of monodisperse polystyrene spheres of 500 nm particle diameter was drop-casted on the carbon tracks printed on the substrate made of alumina ceramic. After evaporation, the electrode was carefully dipped in copper plating solution for a certain time to achieve a sufficient penetration of solution within the polystyrene spheres. The metal was then electrodeposited galvanostatically over the self-assembled colloidal crystal. Finally, the polystyrene template was dissolved in toluene to expose the porous structure of copper deposit. The morphology of porous structures was investigated using scanning electron microscopy. Electroanalytical properties of porous copper film electrodes were evaluated in amperometric detection of selected saccharides, namely glucose, fructose, sucrose, and galactose. Using hydrodynamic amperometry in stirred alkaline solution, a current response at +0.6 V vs. Ag/AgCl was recorded after addition of the selected saccharide. These saccharides could be quantified in two linear ranges (0.2–1.0 μmol L−1 and 4.0–100 μmol L−1) with detection limits of 0.1 μmol L−1 glucose, 0.03 μmol L−1 fructose, and 0.05 μmol L−1 sucrose or galactose. In addition, analytical performance of porous copper electrodes was ascertained and compared to that of copper film screen-printed carbon electrodes, prepared ex-situ by the galvanostatic deposition of metal in the plating solution. After calculating the current densities with respect to the geometric area of working electrodes, the porous electrodes exhibited much higher sensitivity to changes in concentration of analytes, presumably due to the larger surface of the porous copper deposit. In the future, they could be incorporated in detectors of flow injection systems due to their long-term mechanical stability. [ABSTRACT FROM AUTHOR]

Although the basic theory for electrochemical measurement is well known, there is still much to be developed in specific instrumental systems for biosensors, especially to achieve fast response times, usefulness, and low-cost equipment. In this regard, continuous flow analysis (CFA) systems with an integrated biosensor are valuable tools for bioanalysis monitoring. These systems are suitable for automation and monitoring in real time with a short response time. Among biosensors, amperometric ones are the most used due to their high selectivity and wide linear range. In this work, we design and develop all parts of an automated CFA system for bioanalysis based on amperometric biosensors. It consists of several inlets for the samples, standards, and carrier solution; a fluidic subsystem; an electronic subsystem in which output voltage will be directly correlated to the analyte concentration in the solution; and a software application to configure and control all the features of the system. The prototype was successfully validated using an amperometric biosensor to analyze the ethanol content of low-alcohol beers. [ABSTRACT FROM AUTHOR]

Carbon-based electrodes are promising candidates for developing cheap, miniaturized, and disposable biosensors for effective, point-of-care disease management. However, their sensitivity is usually lower than gold electrodes due to polymer binders used during the procedure of ink formulating. Although surface pretreatment with reactive chemicals and addition of nanomaterials are available to enhance their sensor performance, both approaches may suffer from the use of hazardous substances and processing complexity. Here, we report an inexpensive, non-nanomaterials approach by making a graphite/carbon fiber (G/CF) hybrid electrode for biosensor applications. The hybrid electrode is formed by embedding a homemade graphite ink in the CF matrix of a commercially available carbon paper. This design resembles a super-efficient 3D highway network where ample expressways (CF) run through numerous small factories (locally distributed graphite flakes) for rapid goods pick-up and transportation (electron transfer). Featuring high conductivity, low impedance and large active surface area surpassing commercial screen-printed carbon electrodes, the G/CF hybrid electrodes show superior sensor performance for glucose detection as compared to counterparts prepared on electrodes without CF matrix. This study provides a new approach of enhancing electrochemical performance of carbon-based electrodes by structural design using macro-size scale, affordable materials.

Sulfite determination in foods and alcoholic beverages is a common requirement by food and drug administration organisations in most countries. In this study, the enzyme, sulfite oxidase (SOx), is used to biofunctionalise a platinum-nanoparticle-modified polypyrrole nanowire array (PPyNWA) for the ultrasensitive amperometric detection of sulfite. A dual-step anodisation method was used to prepare the anodic aluminum oxide membrane used as a template for the initial fabrication of the PPyNWA. PtNPs were subsequently deposited on the PPyNWA by potential cycling in a platinum solution. The resulting PPyNWA-PtNP electrode was then biofuntionalised by adsorption of SOx onto the surface. The confirmation of the adsorption of SOx and the presence of PtNPs in the PPyNWA-PtNPs-SOx biosensor was verified by scanning electron microscopy and electron dispersive X-ray spectroscopy. Cyclic voltammetry and amperometric measurements were used to investigate the properties of the nanobiosensor and to optimise its use for sulfite detection. Ultrasensitive detection of sulfite with the PPyNWA-PtNPs-SOx nanobiosensor was accomplished by use of 0.3 M pyrrole, 10 U mL−1 of SOx, adsorption time of 8 h, a polymerisation period of 900 s, and an applied current density of 0.7 mA cm−2. The response time of the nanobiosensor was 2 s, and its excellent analytical performance was substantiated with a sensitivity of 57.33 μA cm−2 mM−1, a limit of detection of 12.35 nM, and a linear response range from 0.12 to 1200 μM. Application of the nanobiosensor to sulfite determination in beer and wine samples was achieved with a recovery efficiency of 97–103%.

Wearable film-based smart biosensors have been developed for real-time biomolecules detection. Particularly, interfacial co-assembly of reduced graphene oxide-prussian blue (PB-RGO) film through electrostatic interaction has been systematically studied by controllable pH values, achieving optimal PB-RGO nanofilms at oil/water (O/W) phase interface driven by minimization of interfacial free energy for wearable biosensors. As a result, as-prepared wearable biosensors of PB-RGO film could be easily woven into fabrics, exhibiting excellent glucose sensing performance in amperometric detection with a sensitivity of 27.78 µA mM−1 cm−2 and a detection limit of 7.94 μM, as well as impressive mechanical robustness of continuously undergoing thousands of bending or twist. Moreover, integrated wearable smartsensing system could realize remotely real-time detection of biomarkers in actual samples of beverages or human sweat via cellphones. Prospectively, interfacial co-assembly engineering driven by pH-induced electrostatic interaction would provide a simple and efficient approach for acquiring functional graphene composites films, and further fabricate wearable smartsensing devices in health monitoring fields. [ABSTRACT FROM AUTHOR]

Cyanide is a highly toxic agent that has been frequently used for suicide in South Korea. It is also used in various industrial fields, such as metal plating, in which many accidental cyanide intoxications have occurred. To overcome the disadvantages of conventional cyanide analysis methods, a simple and fast method for the analysis of cyanide in whole blood using ion chromatography (IC) with amperometric detection was developed in this study. Whole blood samples were deproteinized, diluted, and analyzed using an IC–amperometric detection system. The limits of detection and quantitation were 0.1 and 0.2 mg/L, respectively. The method showed good linearity in the range of 0.2 to 50 mg/L with R2 > 0.99. The intra‐ and inter‐assay precision and accuracy values were <10%. The established method was successfully applied to analyze whole blood samples from three cyanide intoxication cases. [ABSTRACT FROM AUTHOR]

Detection of toxic hexavalent chromium in soil, groundwater, industrial effluent, etc., is of significant interest. We demonstrate the electrochemical detection of Cr(VI) using a surface-engineered mesoporous carbon-based material. The mesoporous carbon-based material is obtained by the controlled pyrolysis of a homogenous mixture of Fe and Co complexes of hydrolyzed collagen. The as-synthesized material is subjected to surface engineering by acid treatment. The surface-engineered mesoporous carbon-based material has a surface area as large as 443.28 m2 g−1 with interconnected mesopores. Detection of Cr(VI) was achieved at parts per billion level by electrochemical reduction using the surface-engineered carbon-based electrode at the potential of 0.65 V (Ag/AgCl). The modified electrode has excellent sensitivity (7.75 ± 0.03 × 10−4 µA/ppb) and selectivity, low detection limit (8 ppb), and wide linear range (40–800 ppb). The coexisting other metal ions do not interfere with the amperometric measurement of Cr(VI). The electrode is highly stable and it retains >65% of the initial current during the long-term durability test for an hour. The highly porous nature of the material favors facile mass transport and facilitate electron transfer kinetics. The trace amount of CoFe alloy present in the carbon-based material catalyses the reduction of Cr(VI) at a favourable potential. Electrochemical sensing of Cr(VI) at parts-per-billion level is demonstrated with mesoporous carbon derived from iron- and cobalt-hydrolysed collagen complexes [ABSTRACT FROM AUTHOR]

A novel kind of chiral open-tubular (OT) column was established with homochiral zeolitic imidazolate framework-8 nanomaterials using L-histidine as the chiral carbon center (L-His-ZIF-8). The morphologies of L-His-ZIF-8 nanoparticles and chiral OT column were characterized by scanning electron microscopy. The effects of L-His-ZIF-8 concentrations, pH values, and concentrations of the running buffer on the resolution of the selected chiral compounds were investigated based on miniaturized capillary electrochromatography with amperometric detection system (mini-CEC-AD), respectively. The separation performances of the prepared L-His-ZIF-8@OT chiral columns were explored under the optimal conditions, and the RSDs of run-to-run, day-to-day, and column-to-column reproducibility were less than 6.7% using salbutamol raceme as the model enantiomers. The prepared chiral OT columns have been successfully applied to the enantioseparation of one pair of amino acid enantiomers, two pairs of racemic drugs, and three pairs of neurotransmitter enantiomers. Under the optimum conditions, the prepared OT columns were applied to real-world sample analysis of salbutamol aerosol. The limits of detection of salbutamol raceme were 0.90 μg·mL−1 (S/N = 3), and the recovery was 80.4–82.7%. The assay results indicated that this kind of chiral OT column modified with homochiral L-His-ZIF-8 possesses good reproducibility and stability. This developed mini-OT-CEC-AD system has some attractive characteristics of sensitivity and low cost, providing a potential way for the separation of chiral compounds. [ABSTRACT FROM AUTHOR]

In this work, the electrochemical determination of antioxidant compounds in green coffee beans using a low-pressure chromatographic system based on a single 1-cm length monolithic column is presented. Screening of the antioxidant compounds in green coffee beans using this approach was performed under different elution conditions, considering different supporting electrolyte media and applied potential values at detection. Mass spectra analyses for the structure elucidation of the separated compounds are presented. Under the selected experimental conditions, five chlorogenic acids (3-, 4-, 5-, cis-5-caffeoylquinic acids, and 5-feruloylquinic acid) and caffeine were identified. Resolution values higher than 1.5 were achieved for all identified compounds. The limits of detection for 5-caffeoylquinic acid and caffeine were 9.25 µmol L−1 and 6.73 µmol L−1, respectively. Acetonitrile consumption was of 0.325 mL per analysis. The figures of merit obtained plus the simplicity of the analytical system assembling and handling highlight the high competitiveness of the presented low-cost approach to be used in substitution of HPLC methodologies currently performed to this end, and for further analytical applications in complex matrices. [ABSTRACT FROM AUTHOR]

Abstract Nanoscale Au-ZnO heterostructures were fabricated on 4-in. SiO2/Si wafers by the atomic layer deposition (ALD) technique. Developed Au-ZnO heterostructures after post-deposition annealing at 250 °C were tested for amperometric hydrogen peroxide (H2O2) detection. The surface morphology and nanostructure of Au-ZnO heterostructures were examined by field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), etc. Additionally, the electrochemical behavior of Au-ZnO heterostructures towards H2O2 sensing under various conditions is assessed by chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that ALD-fabricated Au-ZnO heterostructures exhibited one of the highest sensitivities of 0.53 μA μM−1 cm−2, the widest linear H2O2 detection range of 1.0 μM–120 mM, a low limit of detection (LOD) of 0.78 μM, excellent selectivity under the normal operation conditions, and great long-term stability. Utilization of the ALD deposition method opens up a unique opportunity for the improvement of the various capabilities of the devices based on Au-ZnO heterostructures for amperometric detection of different chemicals. Graphical abstract

A novel Platinum nanoparticle (PtNPs) modified Poly(pyrrole‐co‐1‐(2‐Aminophenyl)pyrrole)/Urease film coated Au electrode was designed for amperometric detection of urea. PtNPs quantity, film density and pH were optimized and interference effect of some substances readily found in municipal wastewater and blood was investigated. The biosensor responded to urea with a measurement concentration range of 0.1 to 30 mM, a sensitivity of 31.8 μA mM−1 cm−2, a LOD of 7.58 μM, an accuracy of 104 % and a RSD% of only 0.82. It sensed the concentration of urea in the municipal sewage water with recovery of 97.6 % (n=3) and remained 78 % of its initial response at 28th day. Results confirmed that PtNPs with strong conductivity improved the electron transfer ability of the working electrode. [ABSTRACT FROM AUTHOR]

Enzyme‐based amperometric biosensors are proving to be important analytical tools in several fields such as food, environmental and, in recent years, the biomedical one. This work describes the use of 4,7‐bis(5‐(pyridin‐2‐yl)thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole (TBT) in the development of a tyrosinase‐based biosensor for epinephrine detection. The modifying agent was obtained as a film by electrochemical oxidation of TBT on a gold disk electrode. Electrochemical characterization and scanning electrode microscopy (SEM) images suggest the formation of a conducting film on the electrode surface. Tyrosinase from mushroom was then immobilized by a mixed technique of adsorption and cross‐linking. Glutaraldehyde was used as a coupling agent. The obtained device shows a very good linear response (0.1–50 μM) with a LoD value of 0.06 μM and a LoQ of 0.09 μM. Moreover, good selectivity towards some typical interferents (namely, ascorbic acid, tryptophan, uric acid and L‐cysteine) and satisfactory recoveries have been observed. [ABSTRACT FROM AUTHOR]

The long-term consumption of food with pesticide residues has harmful effects on human health and the demand for pesticide detection technology tends to be miniaturized and instant. To this end, we demonstrated the first application of indirectly detecting two carbamate pesticides, metolcarb and carbaryl, by gold nanoparticle–modified indium tin oxide electrode in dual-channel microchip electrophoresis and amperometric detection (ME-AD) system. m-Cresol and α-naphthol were obtained after pesticide hydrolysis in alkaline solution, and then separated and detected by ME-AD. Parameters including the detection potential and running buffer concentration and pH were optimized to improve the detection sensitivity and separation efficiency. Under the optimal conditions, the two analytes were completely separated within 80 s. m-Cresol and α-naphthol presented a wide linear range from 1 to 100 μM, with limits of detection of 0.16 μM and 0.34 μM, respectively (S/N = 3). Moreover, the reliability of this system was demonstrated by analyzing metolcarb and carbaryl in spiked vegetable samples. [ABSTRACT FROM AUTHOR]

Cu‐MOF/graphene composite were obtained by solvothermal and electrochemical methods. The interaction and formation of Cu‐MOF/graphene (GE) composite was systematically studied with the support of various characterizations including X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM) and cyclic voltammogram (CV). The Cu‐MOF/graphene composite coated glassy carbon (GC) electrode exhibited good catalytic performance towards the electro‐oxidation of caffeine in neutral condition. The modified electrode displayed good linear range (5 μM to 450 μM), sensitivity (0.710 μA μM−1 cm−2), detection limit (1.38 μM), selectivity, high stability and reproducibility. Finally, the fabricated electrode extended into successful detection of caffeine in tea and coffee samples with good recoveries. [ABSTRACT FROM AUTHOR]

The fabrication of a highly selective and ultrasensitive sulfite nanobiosensor based on a layered architectural fabrication aided by the encapsulation of sulfite oxidase (SOx) in Nafion (Naf) matrix on a multiwalled carbon nanotubes-polypyrrole (MWCNTs-PPy) composite decorated with platinum nanoparticles (PtNPs) is described. The MWCNTs are deposited in the inner layer on a Pt electrode during electropolymerization of pyrrole (Py), followed by decoration with a PtNPs layer and subsequent encapsulation of SOx with Naf in the third layer capped with a fourth thin PtNPs layer. Images obtained by field emission scanning electron microscopy (FESEM) reveal that high-density PtNPs are deposited onto the 3D nanostructured inner MWCNTs-PPy layer and the electrochemical behavior is investigated. A large surface area provided by the incorporation of MWCNTs in the composite and decoration with PtNPs enables increased SOx loading, SOx retention, and substantial improvement in sensing performance. The resulting layered PtNPs/SOx-Naf/PtNPs/MWCNTs-PPy nanobiosensor exhibits a fast response time (within 3 s), a linear calibration range of 20 nmm - 6 m with an excellent sensitivity of 71 µA mm -1  cm -2 and a detection limit of 5.4 nm. The nanobiosensor  was effective in discriminating against common interferants and  was successfully applied to sulfite determination in real samples., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)

Hydrogen sulfide (H 2 S) is a pervasive gaseous pollutant that emits the characteristic odor of rotten gas, even at low concentrations. It is generated during various industrial processes, including petroleum and natural gas refining, mining operations, wastewater treatment activities, and refuse disposal practices. According to statistics from the World Health Organization (WHO), over 70 occupations are exposed to H 2 S, rendering it a key monitoring factor in occupational disease detection. Although H 2 S has legitimate uses in the chemical, medical, and other fields, prolonged exposure to this gas can cause severe damage to the respiratory and central nervous systems, as well as other organs in the human body. Moreover, the substantial release of H 2 S into the environment can lead to significant pollution. This noxious substance has the potential to impair soil, water, and air quality, while disrupting the equilibrium of the surrounding ecosystems. Therefore, sulfide has become one of the most commonly measured substances for environmental monitoring worldwide. Achieving the stable enrichment and accurate detection of low-level H 2 S is of great significance. Common methods for detecting this gas include spectrophotometry, chemical analysis, gas chromatography, rapid field detection, and ion chromatography. Although these methods provide relatively reliable results, they suffer from limitations such as high detection cost, low recovery, lack of environmental friendliness, and imprecise quantification of low-concentration H 2 S. Furthermore, the sampling processes involved in these methods are complex and require specialized equipment and electrical devices. Additionally, approximately 20% of the sulfides in a sample are lost after 2 h in a conventional alkaline sodium hydroxide solution, causing difficulties in preservation and detection. In this study, an accurate, efficient, and cost-saving method based on ion chromatography-pulse amperometry was developed for H 2 S determination. A conventional IonPac AS7 (250 mm×4 mm) anion-exchange column was employed, and a new eluent based on sodium hydroxide and sodium oxalate was used to replace the original sodium hydroxide-sodium acetate eluent. The main factors influencing the separation and detection performance of the proposed method, including the pulse amperage detection potential parameters and integration time, as well as the type and content of additives in the stabilizing solution, were optimized. The results showed that the proposed method had a good linear relationship between 10 and 3000 μg/L, with correlation coefficients ( r 2 ) of up to 0.999. The limits of detection ( S/N =3) and quantification ( S/N =10) were 1.53 and 5.10 μg/L, respectively. The relative standard deviations (RSDs) of the peak area and retention time of sulfides were less than 0.2% ( n =6). The new method exhibited excellent stability, with up to 90% reduction in reagent costs. Compared with conventional ion chromatography-pulse amperometry, this method is more suitable for detecting low concentrations of sulfides in actual samples. Sulfides in a 250 mmol/L sodium hydroxide-0.8% (mass fraction) ethylenediaminetetraacetic acid disodium salt solution were effectively maintained for over 10 h. The new stabilizer significantly improved the reliability of both large-scale and long-term detection. The recovery of the proposed method was investigated by combining the system with a badge-type passive sampler. This sampling method requires no power devices; it is inexpensive, simple to operate, and can realize long-term sampling without the need for skilled personnel. Moreover, it can overcome the influence of short-term changes in pollutant concentration. The sampling results have high reference value for large-scale intervention-less pollutant monitoring in ultraclean rooms, museum counters, and other places. The results demonstrated that the recovery of the proposed method was greater than 95% for the blank sample and 80% for the sample plus standard solution. Finally, the newly established method was applied to determine H 2 S levels in air samples collected via passive sampling at school garbage stations. The measured results did not exceed the national limit.

Spatially dispersed redox-active iridium sites are immobilized throughout the porous framework of a zirconium-based metal–organic framework (MOF), UiO-66, to enable charge hopping in the MOF. The resulting iridium sites within UiO-66 not only permit redox hopping-based electron transport within the MOF in aqueous electrolytes, but also exhibit electrocatalytic activity for the oxidation of nitrite. The pH of the electrolyte for this electrocatalysis is optimized, and the electrocatalytic mechanism occurring on the Ir-decorated UiO-66 thin films is investigated. The material is further applied for amperometric nitrite sensing in aqueous solutions. Owing to its high porosity, the Ir-decorated UiO-66 achieves a good sensitivity (168.8 μA/mM-cm2) for detecting nitrite with a low limit of detection (0.41 μM).

A dense zeolitic imidazolate framework (ZIF) nanosheet is for the first time molded by reduced graphite oxide (RGO) and graphitic carbon nitride (g-C3N4) to fabricate an original 2D/2D/2D heterojunction (ZIF/g-C3N4/RGO nanohybrid), which is pipetted onto carbon cloth electrode (CCE) (ZIF/g-C3N4/RGO/CCE) as an electrochemical sensor. Profiting from the renowned synergistic and coupling effects, the resulting nanohybrid endows excellent electrocatalytic activity towards hydrazine. Amperometric detection reveals that the hybrid sensor possesses a low detection limit of 32 nM (S/N = 3) in a monitoring range of 0.0001 to 1.0386 mM, along with a high sensitivity 93.71 μA mM−1 cm−2. Importantly, the minimum detection concentration of hydrazine in the actual sample is lower than the maximum allowable limit of the World Health Organization (WHO) and has high reproducibility (RSD = 4.82%). As expected, the high sensing capability of ZIF/g-C3N4/RGO combines the advantages of abundant surface-active sites and high conductivity along with 2D interfaces between ZIF, g-C3N4, and RGO nanosheets. This study provides a promising to expand 2D-based ternary nanojunction as a bridge for promoting sensing performance. Graphical abstract [ABSTRACT FROM AUTHOR]

Early diagnosis in primary care settings can increase access to therapies and their efficiency as well as reduce health care costs. In this context, we report in this paper the development of a disposable immunoplatform for the rapid and simultaneous determination of two protein biomarkers recently reported to be involved in the pathological process of neurodegenerative disorders (NDD), tau protein (tau), and TAR DNA-binding protein 43 (TDP-43). The methodology involves implementation of a sandwich-type immunoassay on the surface of dual screen-printed carbon electrodes (dSPCEs) electrochemically grafted with p-aminobenzoic acid (p-ABA), which allows the covalent immobilization of a gold nanoparticle-poly(amidoamine) (PAMAM) dendrimer nanocomposite (3D-Au-PAMAM). This scaffold was employed for the immobilization of the capture antibodies (CAbs). Detector antibodies labeled with horseradish peroxidase (HRP) and amperometric detection at − 0.20 V (vs. Ag pseudo-reference electrode) using the H2O2/hydroquinone (HQ) system were used. The developed methodology exhibits high sensitivity and selectivity for determining the target proteins, with detection limits of 2.3 and 12.8 pg mL−1 for tau and TDP-43, respectively. The simultaneous determination of tau and TDP-43 was accomplished in raw plasma samples and brain tissue extracts from healthy individuals and NDD-diagnosed patients. The analysis can be performed in just 1 h using a simple one-step assay protocol and small sample amounts (5 μL plasma and 2.5 μg brain tissue extracts). [ABSTRACT FROM AUTHOR]

Herein we report a reliable and stable biosensor for the amperometric detection of creatinine through the ammonium produced in its reaction with creatinine deiminase linked to a Nafion®/polyaniline gold coated surface. The gold electrode array was produced using a low cost printed board circuit technology. A linear range of 1–1000 μM was obtained with standard deviations of less than 5 % (n=3) obtained. Stability studies were carried out and 80 % activity was maintained after one month. The sensors were tested with 142 serum samples from patients with renal dysfunction at different stage of the disease and validated using a commercial colorimetric method. [ABSTRACT FROM AUTHOR]

The reactive oxygen species (ROS) generated during the course of many metabolic processes are capable of oxidizing biologically active compounds (BAC). The total water-soluble antioxidant contents (TWSAC) in the model and biological fluids are determined with the amperometric method (TsvetYauza-01-AA chromatography device, Russia). Thus, the TWSAC for biologically active ascorbic acid, sea buckthorn, white grapes, and amino acids (AAs) comprised 46.53, 0.54, 0.28, and 4.00 mg/g, respectively (as the average value for their blood content). The TWSAC in the blood sera of cattle in different age and sex groups, kept under comparable experimental conditions, ranged from 14.8 to 21.3 mg/g. The water-soluble antioxidant level in youngstock (3 months old) was significantly higher than that in lactating cows, which is probably due to the higher serum concentrations of aromatic AAs having powerful antioxidant properties in the young specimens. The datasets generated during the current study are important in assessing the physiological and biochemical status and evaluating the efficiency of the antioxidant defense systems in the body of an animal. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of o‐cresol and p‐cresol was investigated using boron doped diamond (BDD) and sp2 carbon‐based electrodes. BDD electrodes with different boron doping levels were used to optimize conditions for detection of cresols using differential pulse and square‐wave voltammetry. Comparable detection limits from 2.74 μM to 0.79 μM were achieved, using in‐situ anodic pretreatment to prevent fouling of electrode surface. Lower detection limits for cresols and other phenolic pollutants, in the 10−7 M concentration range, were obtained using amperometric detection in HPLC. The proposed voltammetric and HPLC methods were utilized for determination of cresols in model river water samples. [ABSTRACT FROM AUTHOR]

A flow injection analysis with integrated amperometric alcohol dehydrogenase biosensor and a handheld Mira‐DS Raman spectrometer have been compared for the determination of ethanol in different samples of alcoholic drinks. The biosensor was constructed from the commercial screen‐printed carbon electrode as amperometric transducer and covered by a thin layer comprising alcohol dehydrogenase, reduced single‐layer graphene oxide, rhodium(IV) dioxide, and glutaraldehyde. Both assemblies were tested on analysis of plum brandy, white rum, vodka, white and red wines, strong dark beer, and non‐alcoholic beer. The two principally different analytical methods were critically compared and some limitations found, especially in case of analysis of red wine and beers. Finally, some future improvements of both analytical tools under test outlined. [ABSTRACT FROM AUTHOR]

The whole grain intake is closely associated with human health. In this work, three‐phase dynamic hollow‐fiber liquid‐phase microextraction reinforced with 0.10 mg/mL 30 nm zeolitic imidazolate framework‐8 nanoparticles was introduced for purification and enrichment of free urinary metabolite biomarkers of whole grain intake. Eight milliliters of HCl (pH 3.00) and 8 μL of 300 mM NaOH solutions were used as the donor and acceptor phases, respectively. The temperature and stirring rate were kept at 25℃ and 500 rpm, and the extraction time was 40 min. The extraction process required no further desorption, and the resultant extract was directly used for electrophoretic analysis without derivatization. Based on the synergistic effect of hollow‐fiber liquid‐phase microextraction and the electrophoretic stacking, the enrichment factors of 3,5‐dihydroxybenzoic acid and 3‐(3,5‐dihydroxyphenyl)‐1‐propionic acid reached 1018–1034 times, and their limits of detection achieved 0.33–0.67 ng/mL (S/N = 3) in urine matrix. The developed method has been successfully used for urine analysis, and the sample recovery data were in the range of 97.0–103.5%. This developed method provided an attractive alternative for the determination of urinary metabolite biomarkers of whole grain intake due to its sensitive, fast, low‐cost, and environmental‐friendly features. [ABSTRACT FROM AUTHOR]