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Hydroquinone (HQ), a phenolic compound is expansively used in many industrial applications and due to the utilization of HQ, water pollution tragedies frequently found by the improper handling and accidental outflows. When HQ is adsorbed directly through the skin that create toxic effects to human by affecting kidney, liver, lungs, and urinary tract and hence, a highly selective and sensitive technique is required for its quantification. Herein, we have developed the ultrasonic synthesis of copper oxide nanoflakes (CuO-NFs) using ultrasonic bath (20 kHz, 100 W) and successfully employed for the sensitive detection of the environmental hazardous pollutant HQ. The formed CuO-NFs were confirmed by X-ray diffraction, field emission scanning electron microscopy (FE-SEM), FT-IR spectroscopy and UV-visible spectroscopy and fabricated with the screen-printed carbon electrode (SPCE). The SEM images exhibited the uniform CuO-NFs with an average width of 85 nm. The linker-free CuO-NFs fabricated electrode showed the appropriate wide range of concentrations from 0.1 to 1400 µM and the limit of detection was found to be 10.4 nM towards HQ. The fabricated sensor having long term stability and sensitivity was successfully applied for the environmental and commercial real sample analysis and exhibited good recovery percentage, implying that the SPCE/CuO-NFs is an economically viable and benign robust scaffold for the determination of HQ., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We report here graphene-like carbon nanosheets (GCN) as a new electrode material for the electrochemical determination of hydroquinone (HQ) and catechol (CC). The GCN were prepared from maltose using ammonia chloride as a blowing agent and cobalt nitrate as a graphitization catalyst precursor. The as-prepared GCN material shows high graphitization degree, abundant porosity, and large specific surface area. Two well-separated anodic peaks for HQ and CC are obtained at GCN modified glassy carbon electrode (GCE) with a peak-to-peak separation of 118mV. The redox peak currents of HQ and CC at GCN/GCE were much higher than those at bare GCE and reduced graphene oxide modified GCE. For differential pulse voltammetric detection of HQ and CC, the GCN/GCE shows linear response ranges of 1×10 -7 ̶ 3×10 -5 M for HQ and 5×10 -7 ̶ 5×10 -5 M for CC, with detection limits of 2×10 -8 M for HQ, and 5×10 -8 M for CC. Satisfactory recoveries were achieved for the determination of HQ and CC in real water samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Flow injection amperometric (FI-Amp) sensor was developed for sensitive and selective determination of hydroquinone. A simple screen printed carbon electrode (SPCE) was modified with various nanomaterials for improvement of sensitivity on the determination of quinone. As a result, the appropriate sensitivity is obtained from the SPCE modified with carbon nanotube (CNT) which indicated that CNT contributed to the transfer of electron to quinone. The reproducibility (n=9) and repeatability (n=111) of SPCE-CNT were obtained at 4.4% and 3.6%RSD, respectively. The SPCE-CNT electrode and enzymatic column were incorporated to the FI-Amp system to determine hydroquinone. Laccase was immobilized on silica gel using a cross-linking method by glutaraldehyde modification and then packed in the column. The laccase column has high efficiency for catalytic oxidation of hydroquinone to quinone, which further detects by amperometric detection. Parameters affecting response of the proposed sensor, i.e., pH, ionic strength, and temperature have been optimized. The proposed system provided a wide linear range between 1 and 50 µM with detection limit of 0.1 µM. Satisfactory recoveries in the range of 91.2-103.8% were obtained for the analysis of water sample., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A synergistic electrocatalytic effect was observed in sensors where two electrocatalytic materials (functionalized gold nanoparticles and lutetium bisphthalocyanine) were co-deposited using the Langmuir-Blodgett technique. Films were prepared using a novel method where water soluble functionalised gold nanoparticles [(11-mercaptoundecyl)tetra(ethylene glycol)] (SAuNPs) were inserted in floating films of lutetium bisphthalocyanine (LuPc2) and dimethyldioctadecylammonium bromide (DODAB) as the amphiphilic matrix. The formation of stable and homogeneous mixed films was confirmed by π-A isotherms, BAM, UV-vis and Raman spectroscopy, as well as by SEM and TEM microscopy. The synergistic effect towards hydroquinone of the electrodes modified with LuPc2:DODAB/SAuNP was characterised by an increase in the intensity of the redox peaks and a reduction of the overpotential. This synergistic electrocatalytic effect arose from the interaction between the SAuNPs and the phthalocyanines that occur in the Langmuir-Blodgett films and from the high surface area provided by the nanostructured films. The sensitivity increased with the amount of LuPc2 and SAuNPs inserted in the films and limits of detection in the range of 10(-7)molL(-1) were attained., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Organic redox molecules have attracted considerable attention because of their abundant availability and excellent design flexibility. For practical applications, these molecules must be anchored onto scaffolds such as polymers to prevent crystallization and elution into the electrolyte. In this study, we explore the use of polyhedral oligomeric silsesquioxane (POSS) derivatives as scaffolds for anthraquinone (AQ) and hydroquinone. We investigated the cage structure of POSS and the number of redox units incorporated. Notably, a corner‐opened POSS (CO‐POSS) variant with three AQ units exhibited reversible redox behavior under neutral, acidic, and basic conditions. Furthermore, we examined the air‐battery performance of AQ‐modified CO‐POSS as an anode‐active material. [ABSTRACT FROM AUTHOR]

Tert-butyl hydroquinone (TBHQ) is a member of the synthetic phenolic antioxidant family that prevents the formation of free radicals and prevents radicals from damaging cells by trapping them. In addition, TBHQ is widely preferred as an additive in foods and vegetable oils because of its low cost and high chemical stability. TBHQ is not only a food preservative but is also frequently used as a stabilizer to prevent auto-polymerization in cosmetics, biodiesel, pharmaceuticals, coating products, and different application areas. TBHQ has been shown to cause diseases, such as DNA damage, carcinogenesis, and cell apoptosis, when administered at high doses. Excessive consumption of TBHQ causes adverse effects, such as stomach tumors, liver damage, and underdevelopment of the reproductive system. Different analytical methods have been used to detect TBHQ in food samples. The most important of these methods are traditional analytical methods such as chromatographic and spectrophotometric methods. However, these methods have basic shortcomings such as high analysis costs, long pre-processing, expensive equipment, need for many organic solvents, requiring expertise, and long detection times. In recent years, electrochemical sensors have attracted attention in the scientific world owing to their high sensitivity, fast analysis time, portability, low cost, and convenience of miniaturization. This review discusses electrochemical studies performed to date for the determination of TBHQ in food samples. The methods used in these studies have been evaluated in a wide range of aspects, such as the electrode, working range, detection limits, and analytical applications. [ABSTRACT FROM AUTHOR]

Full mineralization of organic pollutants is a tough task with existing technologies. Even if all conventional energies and extremes are exhausted, high-temperature wastewater treatment is not worth the loss from the perspective of energy. Solar engineering holds promise for the full mineralization of organic pollutants to tackle the global fossil energy shortage. Here, we report solar engineering for full mineralization and efficient solar utilization. The solar energies and spectrum were fully utilized to initiate the solar heat and solar electricity. Two energies were applied to trigger the thermochemical and electrochemical oxidation of the organic pollutants. Our study bridges the gap between the energy and environment towards efficient solar utilization and effective water treatment. As a proof-of-concept study, this demonstrates a solar engineering of full phenol mineralization in wastewater. A record phenol mineralization rate was achieved to reach an oxidation rate of 98% and COD of 93% under a constant current density of 50mA/cm2 at 150°C. UV and HPLC were used to detect the intermediate products during variable time intervals. The results showed that the intermediate products are composed of maleic acid, hydroquinone and p-benzoquinone. In the extreme high temperature (90°C), the solar oxidation time and pathway are greatly altered. The reaction rate constant at 150°C is about 11 times than that at 90°C. More solar heat significantly reduces the activated energy of the pollutant oxidation and lowers the potential of electrolysis. [ABSTRACT FROM AUTHOR]

This work shows that the cup-stacked carbon nanotube/carbon fiber felt composite electrode (CSCNT/felt) is a promising electronic conductive matrix to develop biosensors. The device was prepared by combining this matrix with the well-studied enzyme tyrosinase. Atomic force microscopy and scanning electron microscopy confirm that tyrosinase remained well dispersed in the whole electrode and completely covered the CSCNT network surface deposited on the surface of each graphitic felt electrode fiber. The studied combination allows preparing a disposable biosensor to determine hydroquinone in water with remarkable selectivity and accuracy when applied in real samples. The limit of detection was 1.4 µM with a wide linear range between 9 and 545 µM. The device presented good reproducibility for construction, with relative error of 2.4% (n = 7). These results confirm that a simple and sensitive device has been constructed to quantify hydroquinone in natural water and that the CSCNT structure is attractive for the immobilization of tyrosinase without functionalization of their walls or the use of surfactants. [ABSTRACT FROM AUTHOR]

In this work, for the first time, the electrochemical behavior of hydroquinone (H2Q) by linear voltammetry in aqueous reverse micelles (RMs) of sodium 1,4‐bis(2‐ethylhexyl) sulfosuccinate (AOT)/n‐heptane, as well in homogenous media at different pH values, were studied. The choice of this molecular probe is because of its electrochemical response in water, strongly depend on the pH value thus, our goal is to know more about an intriguing issue in the soft matter field, what is the pH value for water encapsulated in the water pool of AOT RMs. Our work will demonstrate that the interfacial apparent pH value of AOT RMs is not strongly acidic as some of the literature works claim, but it is around a pH value of 6.7. Thus, through the electrochemistry technique, the present work reinforces the idea that the concept of is strongly dependent on the water‐interface interactions and the molecular probe location. [ABSTRACT FROM AUTHOR]

An electrochemical sensor is described for the simultaneous determination of hydroquinone (HQ) and catechol (CC) based on a nanocomposite consisting of gold nanoparticles and graphitic carbon nitride (g-C3N4). The nanocomposite was synthesized via one-step thermal polymerization route and characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared techniques. The results confirmed the close contact between gold nanoparticles and g-C3N4. The nanocomposites exhibited the enhanced electrocatalytic redox towards HQ and CC. A glassy carbon electrode was modified with the nanocomposite to obtain a sensor that exhibited favorable analytical properties in the simultaneous detection of HQ and CC, with voltammetric peaks typically near −0.14 and − 0.02 V (vs. saturated calomel electrode). Linear responses are found between 1.0 and 320 μM for HQ (with a 0.3 μM detection limit; at S/N = 3), and between 0.1 and 320 μM for CC (with a 0.04 μM detection limit; at S/N = 3). The sensor was applied for the simultaneous determination of HQ and CC in spiked water samples, and acceptable recoveries were achieved. The superior sensing properties of the electrode are attributed to the synergy between the microstructure (heterojunction and porosity) and the π interactions between phenolic isomers and g-C3N4. [ABSTRACT FROM AUTHOR]

It is needed to speed up the development of a sensitive detection platform for simultaneous determination of dihydroxybenzene isomers with harmful properties. Here, two isomorphic Metal–organic frameworks (MOFs) [Zn(Trz)(R-BDC)1/2] (FJU-40-R, R = H or NH2; Trz = 1,2,4-Triazole; H-BDC = terephthalic acid) were selected to derive two N-doping porous carbon (NPC) materials. Further, a strategy for constructing electrochemical sensors for simultaneous determination of hydroquinone (HQ) and catechol (CT) was proposed by the MOF-derived NPC modifying glass carbon electrode (GCE). It was found that HQ and CT had good responses on NPC-FJU-40-H/GCE, but had no obvious responses on NPC-FJU-40-NH2/GCE. NPC-FJU-40-H/GCE displayed excellent reproducibility, stability, and anti-interference. Under the optimal conditions, the linear ranges of HQ and CT on NPC-FJU-40-H/GCE were 1 ~ 70 µmol L−1 and 1 ~ 100 µmol L−1 with the detection limits of 0.18 µmol L−1 for HQ and 0.31 µmol L−1 for CT, respectively. Although the porous carbon (PC) derived from MOFs has been applied in electrochemical sensing, the effect of the ligand functional groups of isomorphic MOFs on the electrochemical properties of the derived PC materials is still lack of relevant research. Our research provided an idea that the electrocatalysis properties of MOF-derived porous carbon materials could be tuned by changing the functional groups in ligands of isomorphic MOFs in electrochemical sensing field. A feasible strategy was proposed by changing the ligands of the two isomorphic MOFs (FJU-40-H and FJU-40-NH2) to tune the electrocatalysis properties of MOF-derived N-doped porous carbon materials for the simultaneous determination of dihydroxybenzene isomer. [ABSTRACT FROM AUTHOR]

Abstract The electrochemical study of Catechol (CC) was studied in presence of Hydroquinone (HQ) using poly(murexide) modified glassy carbon electrode (MGCE) by cyclic voltammetric study. The modified electrode exhibited good affirmative response towards the electro chemical oxidation of CC in presence of HQ in 0.2 M phosphate buffer solution at the physiological of pH 7.4. The influence of scan rate, concentration and pH parameters were examined with the cyclic voltammetric method. The modified electrode showed good selectivity and sensitivity with an advantage of interference study and free determination of selected analytes in this experiment. Finally a simple, sensitive and selective method was developed for the determination of dihydroxybenzene isomeric compounds. Graphical abstract Unlabelled Image Highlights • Electropolymerisation of murexide on the surface of glassy carbon electrode • Electrocatalytic activity towards the determination of catechol and Hydroquinone • Modified electrode showed good selectivity and sensitivity. • A simple selectivity and selectivity procedure was reported. [ABSTRACT FROM AUTHOR]

In this work, ZIF-67 decorated with polyacrylonitrile (PAN) was electrospun to obtain composite ZIF-67/PAN nanofibers, which were used to construct C-ZIF-67/PAN-800 via one-step pyrolysis at 800 °C under a N2 atmosphere. Then, a strategy for constructing a sensor for the simultaneous determination of hydroquinone (HQ) and catechol (CC) was proposed using a C-ZIF-67/PAN-800-modified glass carbon electrode (GCE). Additionally, C-ZIF-67-800 was fabricated as a reference through the pyrolysis of ZIF-67 in the absence of PAN at 800 °C. C-ZIF-67/PAN-800/GCE showed much better electrochemical activity for the simultaneous determination of HQ and CC than C-ZIF-67-800/GCE. Under optimal conditions, C-ZIF-67/PAN-800/GCE exhibited a wide detection range of 1–120 μM and 1–200 μM for HQ and CC, respectively, and both detection limits were 1.0 μM. Our work proves that the electrochemical properties of MOF-derived porous carbon materials can be tuned by electrospinning. [ABSTRACT FROM AUTHOR]

Several new electroactive diquinone and dihydroquinone derivatives of calix[4]arene bearing anchor functional groups were designed, synthesized and characterized. A method for selective protection of the hydroquinone –OH groups with trimethylsilyl groups (TMS) either on lower-rim or on upper-rim was developed. Four selected molecules - with sulfide anchor groups and carboxylic anchor groups - were adsorbed onto Au(111) single crystal surface using ex-situ and in-situ self-assembly methods. Adsorbed molecules were then electrochemically probed with cyclic voltammetry. All adsorbed molecules showed redox response which changed during cycling. After conditioning CVs stabilized and showed two distinct current peaks for all molecules. Synthesized and electrochemically probed molecules are of interest to: Li-ion batteries (as cathode materials and overcharge protection), beyond Li-ion batteries and redox-flow batteries.

Graphical abstract The study reports one strategy for fabrication of octadecylamine-functionalized graphene vesicles (OA-GV) using a Pickering the soft template. The as-prepared OA-GV offers a large specific surface, high catalytic ability and electrochemical activity. The glassy carbon electrode modified with OA-GV exhibits an ultrahigh sensitivity for detection of hydroquinone, because a significantly electrochemical synergy was achieved. Highlights • The study reports synthesis of octadecylamine-functionalized graphene vesicles. • The vesicles offers a large surface area, high conductivity and high catalytic activity. • The introduction of octadecylamine achieves to highly electrochemical activity. • The sensor based on vesicles an exhibits an ultra high sensitivity to hydroquinone. • The study offers approach for building on graphene aerogel for further application. Abstract The study reports one strategy for synthesis of octadecylamine-functionalized graphene vesicles (OA-GV). Firstly, citric acid was mixed with octadecylamine and subsequently heated at 180 °C for 4 h to form a graphene oxide that consists of small graphene sheets with a good amphiphilic structure. The graphene oxide was dispersed in water and strongly mixed with toluene to produce a toluene-in-water Pickering emulsion. The graphene oxide sheets in the emulsion were orderly self-assembled into graphene oxide micro-gel in the toluene/water interface. Followed by freeze-drying and thermal reduction in H 2 at 400 °C for 5 h. The as-synthesized OA-GV shows a vesicle-like architecture constructed by ultrathin graphene sheets. The use of small graphene oxide sheets and their self-assembly effectively avoid the serious agglomeration of graphene sheets and leads to a large specific surface area (1853.2 m2 g−1). The introduction of octadecylamine creates highly electrochemical activity and helps to achieve a significant synergy in electrochemistry between OA-GV and hydroquinone. The sensor based on OA-GV exhibits an ultrahigh sensitivity towards hydroquinone. The differential pulse voltammetric peak current linearly increases with the increase of hydroquinone in the range of 0.01–1.0 nM with the detection limit of 0.0049 nM (S/N = 3). The method has been successfully applied to determination of hydroquinone in water samples. [ABSTRACT FROM AUTHOR]

Abstract: Widening the voltage window is often proposed as a way to increase the energy density of aqueous supercapacitors. However, attempting to operate beyond the aqueous supercapacitor stability region can undermine the supercapacitor reliability due to pronounced electrolyte decomposition, which can lead to a significant self‐discharge process. To minimize this challenge, charge injection by grafting o‐benzenediol onto the carbon electrode is proposed through a simple electrochemical cycling technique. Due to charge injection from o‐benzenediol into the carbon electrode, the equilibrium potential of the individual electrode can be reduced. In addition, due to its small molecular size, charge distribution, which is commonly faced by bulk pseudocapacitive materials, is also avoided. The assembled supercapacitor based on the o‐benzenediol‐grafted carbon demonstrated a maximum energy density of 24 Wh kg−1 and a maximum power density of 69 kW kg−1, with a retention of 89 % after 10 000 cycles at 10 A g−1. A low self‐discharge of about 4 h was recorded; this could be attributed to the low driving force arising from the lower equilibrium potential. Thus, the proposed technique may provide insight towards the tuning of the equilibrium potential to attain reliable, high‐performing supercapacitors with a low self‐discharge process. [ABSTRACT FROM AUTHOR]

In this paper, we developed a direct way for the study of hydroquinone oxidation through in situ electrochemistry-combined nuclear magnetic resonance (EC-NMR). Electro-polymerization-induced nano-polyaniline film was utilized as the catalyst in the process of electrochemical oxidation of hydroquinone. In situ EC-NMR provides a powerful tool to probe products distribution and reaction rate, which could be useful to investigate electro-catalytic mechanism and evaluate the electro-catalytic capacity. To study the influence of both protic and aprotic media in the electrocatalytic process, we mixed water and dimethylsulfoxide to mimic possible real-life electrochemical environments. The proposed in situ EC-NMR is capable of quantitatively monitoring the generation of products under varied solvent composition and pH values. A positive effect to electro-catalysis capacity is observed when the concentration of DMSO or water is increased from the volume equivalent point, implying that there should be a competition between protic and aprotic media, which can be characterized by EC-NMR technique. [ABSTRACT FROM AUTHOR]

An elegant hanging-droplet or meniscus-based setup is proposed to carry out quantitative electrolyses from either an organic (hydroquinone) or an inorganic (permanganate) substrate. These examples validate the concept of using such easily accessible, fast (1–3 min) and low-cost operating conditions not only for preparative applications (electrosynthesis), but also for pedagogical purposes in minute samples. [ABSTRACT FROM AUTHOR]

The electrochemistry of hydroquinone (HQ), catechol (CT), and dopamine (DP) on a glassy-carbon electrode (GCE) modified with chemically (CRGO) and electrochemically reduced graphene oxide (ERGO) was investigated and compared for the development of amperometric and voltammetric sensors. Cyclic voltammetric measurements showed higher current on the CRGO-modified GCE, which can be explained by the higher number of sheets compared with ERGO-modified as revealed by SEM images as well as higher roughness surface monitored by AFM, indicating a higher electroactive area. Electrochemical impedance spectroscopy (EIS) revealed that both modified surfaces presented a very similar behavior (Nyquist plots) and lower resistance to electron transfer in comparison with the unmodified GCE. Considering both modified electrodes for sensing purposes, differential-pulse voltammetry (DPV) in unstirred solutions and amperometry under hydrodynamic solutions showed higher sensitivity and lower limit of detection (LOD) values for HQ, CT and DP on the CRGO-modified GCE. These results indicate that the effect of surface rugosity and electroactive area of RGO modified electrodes contribute to the improvement of sensing characteristics of phenolic compounds using either DPV or amperometric detection under flow conditions. DPV and amperometry provided LOD values between 1 and 5 nmol L −1 and 12 and 55 nmol L −1 , respectively, while the latter offers much faster responses resulting in theoretical analytical frequency higher than 1000 h −1 . [ABSTRACT FROM AUTHOR]

Bio-inspired and environmentally friendly chemical functionalization is a successful way to a new class of hybrid electrode materials for applications in energy storage. Quinone (Q)-hydroquinone (QH 2 ) couples, a prototypical example of organic redox systems, provide fast and reversible proton-coupled electron-transfer reactions which lead to increased capacity. To achieve high capacitance and rate performance, constructing three-dimensional (3D) continuous porous structure is highly desirable. Here we report the hybrid electrodes (GA-C) consisting of 3D graphene aerogel (GA) functionalized with organic redox-active material, catechol derivative, for application to high-performance supercapacitors. The catechol derivative is adsorbed on the surface of GA through non-covalent interactions and promotes fast and reversible Q/QH 2 faradaic reactions, providing large specific capacitance of 188 F g −1 at a current of 1 A g −1 and a specific energy of ∼25 Wh kg −1 at a specific power of ∼18,000 W kg −1 . 3D continuous porous structure of GA electrode facilitates ion and electron transports, resulting in high rate performance (∼140 F g −1 at a current of 10 A g −1 ). [ABSTRACT FROM AUTHOR]

In this study, a new electrochemical sensor was developed and fabricated based upon the electrochemical polymerization of neutral red (NR) on the surface of carbon paste electrode (CPE). The newly developed sensor shows electrocatalytic capability towards the simultaneous determination of catechol (CC) and hydroquinone (HQ) in presence of 0.2 M phosphate buffer solution (PBS) at pH 7.4 with the scan rate of 50 mV s − 1 . Electrochemical measurements were performed using both cyclic voltammetry (CV) and differential pulse voltammetric (DPV) methods at poly (neutral red) modified carbon paste electrode (PNR/MCPE). The effects of scan rate, concentration and pH variation for CC and HQ was investigated at PNR/MCPE. The proposed sensor exhibits adsorption-controlled type of electrode process, moreover it show good detection limit (LOD) (CC = 6.46 μM and HQ = 4.97 μM) and limit of quantification (LOQ) (CC = 21.5 μM and HQ = 16.5 μM). Hence, the proposed sensor was successfully applied in the simultaneous determination of CC and HQ with satisfied results. [ABSTRACT FROM AUTHOR]

Sinusoidal voltages (SV) of fixed frequency were used in the preparation of electrochemical biosensors based on gold (Au) disk microelectrode arrays (MEAs) modified with a bio-composite material consisting of poly(3,4-ethylenedioxythiophene) conducting polymer (PEDOT) and tyrosinase (Tyr). The SV was applied over a d.c. potential of 0.60 V vs. Ag/AgCl/KCl (3 M) in order to assess the contribution of the sinusoidal signal to the electrochemical polymerization of the monomer. The use of SV with fixed frequency ensured the preparation of bio-composite materials with given properties. A high porosity is expected, as the Tyr enzyme is entrapped within the polymeric layer by electrostatic interactions during the electrochemical polymerization process. The morphology and the chemical nature of the prepared coatings were studied by scanning electron microscopy, optical profilometry, and infrared reflection absorption spectroscopy. The MEA devices present two independent arrays separated by an insulating gap. One electrode from the device was modified by a PEDOT-Tyr layer, while the second electrode was modified with a PEDOT layer. The analytical determination of dopamine and hydroquinone was carried out via bipotentiostatic measurements by simultaneous polarization of both PEDOT-Tyr and PEDOT modified electrodes from one device using cyclic voltammetry. The analytical performance in terms of linear range, detection and quantification limits, sensitivity, repeatability, re-usability and operational stability, have been assessed. The PEDOT-Tyr based biosensor, prepared at 0.60 V d.c. potential value and SV signal with 50 mHz frequency and ±350 mV amplitude, exhibited a low detection limit of 2.4 × 10 −7 M dopamine, an excellent repeatability of 4.1%, and a recovery of 100.2% were achieved for dopamine determination. The proposed biosensor was also successfully applied in dopamine electroanalysis in pharmaceutical products. [ABSTRACT FROM AUTHOR]

A sensitive and rapid method for the determination of the clinically relevant biomarker receptor tyrosine kinase AXL in serum involving amperometric disposable immunosensors is reported. The target protein was sandwiched between a specific capture antibody covalently immobilized on screen-printed carbon electrodes modified with electropolymerized poly(pyrrolepropionic acid) and a biotinylated detector antibody labeled with a streptavidin-horseradish peroxidase conjugate. The amperometric responses were measured at −0.20 V vs the Ag pseudo-reference electrode of the SPCE upon the addition of H 2 O 2 in the presence of hydroquinone (HQ) as mediator. This integrated immunosensing platform showed a low limit of detection (337 pg mL −1 ), a good selectivity against other non-target serum proteins, and provided results statistically in agreement with those obtained by using a commercial ELISA kit. These attractive features together with the simplicity and easy automation and miniaturization of the required instrumentation make the developed methodology a promising alternative in the development of devices for on-site clinical analysis. [ABSTRACT FROM AUTHOR]