Enhanced Electrochemical Determination of Catechol and Hydroquinone Based on Pd Nanoparticles/Poly(Taurine) Modified Glassy Carbon Electrode

Here, Pd nanoparticles and poly(taurine) film was prepared on the glassy carbon electrode surface (Pd/Poly(TAU)/GCE) by the rapid electrochemical technique. The proposed composite surface was characterized by scanning electron microscopy(SEM), X‐ray photoelectron spectroscopy(XPS) and electrochemical impedance spectroscopy(EIS). Enhanced electron transfer ability and higher electroactive surface area were achieved at Pd/Poly(TAU)/GCE as compared to the bare GCE and polymer film electrode. The new and highly stable Pd/Poly(TAU)/GCE was employed for the individual and simultaneous determination of hydroquinone and catechol which were environmentally toxic. Under the optimized conditions, HQ and CC were individually determined by using the differantial pulse voltammetry in the linear ranges of 0.008–100 μM and 0.001–100 μM with the detection limits of (LOD) 2.1 nM and 0.68 nM, respectively. In case of simultaneous determination, LODs were found as 10 nM and 0.88 nM for HQ and CC, respectively. The content of both analytes in the real sample analysis was evaluated in the river water and tap water successfully.     

Simultaneous Determination of Catechol and Hydroquinone on Nano-Co/L-Cysteine Modified Glassy Carbon Electrode

In this study, a novel and highly sensitive electrochemical method for simultaneous determination of catechol (CC) and hydroquinone (HQ) was developed, which worked at GCE modified with Nano cobalt (Nano-Co) by electrodeposition and L-Cysteine by electrochemical polymerization. The Nano-Co/L-Cysteine GCE was investigated by cyclic voltammetry (CV), SEM and EIS. The excellent conditions have been selected including supporting electrolyte, pH, accumulation time and scan rate. The calibration curves of were obtained that the linear regression equation was I=0.0734c+6×10⁻⁶ in the range of 5.8 μM to 103 μM (R²=0.9942) for CC and the linear regression equation was I=0.0566c+5×10⁻⁶ in the range of 5.8 μM to 100 μM (R²=0.9967) for HQ. The obtained detection limits of CC and HQ both were 6×10⁻⁷ M. The modified electrode was successfully applied to the simultaneous determination of CC and HQ in water samples.     

Sensitive and Facile Determination of Catechol and Hydroquinone Simultaneously Under Coexistence of Resorcinol with a Zn/Al Layered Double Hydroxide Film Modified Glassy Carbon Electrode

A stable dihydroxybenzene sensor was fabricated by electrochemical deposition of Zn/Al layered double hydroxide film on glassy carbon electrode (LDHf/GCE). The sensitive and facile electrochemical method for the simultaneous determination of catechol (CA) and hydroquinone (HQ) under coexistence of resorcinol (RE) has been achieved at the LDHf/GCE in phosphate buffer solution (pH 6.5). Under the optimized conditions, the differential pulse voltammetry response of the modified electrode to CA (or HQ) shows a linear concentration range of 0.6 μM to 6.0 mM (or 3.2 μM to 2.4 mM) with a correlation coefficient of 0.9987 (or 0.9992) and the calculated limit of detection is 0.1 μM (or 1.0 μM) at a signal‐to‐noise ratio of 3. In the presence of 50 μM isomer, the linear concentration ranges for CA and HQ are 3.0 μM to 1.5 mM and 12.0 μM to 0.8 mM, respectively. The detection limits are 1.2 μM and 9.0 μM. Further, the proposed method has been performed to successfully detect dihydroxybenzene isomers in analysis of real samples, such as water and tea.     

Simultaneous determination of hydroquinone and catechol based on three-dimensionally ordered macroporous polycysteine film modified electrode

A three-dimensionally ordered macroporous (3DOM) polycysteine (PCE) film was electropolymerized on the glassy carbon electrode (GCE) using polystyrene spheres as template. The electrochemical behaviors of hydroquinone (HQ) and catechol (CC) were studied, and two independent oxidation peaks were observed. Compared with the bare GCE and GCE modified with PCE without using template, this electrode displays larger peak currents which may be attributed to the structure of PCE and the large surface area of the nanopore array structure. As a result, a novel electrochemical method was developed for the simultaneous determination of HQ and CC. Under the optimized conditions, the peak currents were linear to concentrations in the wider ranges of 9 to 700 μM for HQ and from 3 to 700 μM for CC. The method was successfully applied to the simultaneous determination of HQ and CC in spiked water samples, and the results are satisfactory.     

Simultaneous detection of hydroquinone and catechol on electrochemical-activated glassy carbon electrode by simple anodic and cathodic polarization

Herein, we report a simple method of simultaneous detection of hydroquinone (HQ) and catechol (CC) by cyclic voltammetry (CV) using activated glassy carbon electrodes (GCE). It was found that the two isomers can be completely separated by CV method on cathode polarized GCE (PGCE) after its anodic oxidation. This facile processing method solves the difficulty of electrode surface regenerating which disturb most modified electrodes for the complex composition ease of being contaminated by the analytes in measurement. Morphology and composition of the PGCE were characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectra, and X-ray photoelectron spectroscopy. In addition, the reaction kinetic of HQ and CC reaction on the PGCE was investigated. It was found that the reaction kinetics of HQ and CC is a surface adsorption-controlled process at low concentration and a diffusion-controlled process at high concentration.     

Electrochemical behavior of dihydroxybenzene isomers at MWCNTs modified electrode and simultaneous determination in neutral condition

Simultaneous determination of dihydroxybenzene isomers in neutral condition was successfully realized by a simple and easy prepared modified electrode without previous chemical or physical separations. The multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE), which was prepared by the drop-coating method, was characterized by FE-SEM and TEM. Then, the electrochemical behavior of dihydroxybenzene isomers at MWCNTs/GCE was systematically studied at different temperature and pH conditions. The oxidation peak potentials were separated in neutral condition with 105 mV to hydroquinone (HQ) and catechol (CC) and 390 mV to CC and resorcinol (RS). And in neutral condition, the amperometric current were found to be linear with concentration of HQ, CC, and RS (20–140 μM) with the presence of 100 μM other isomers. Furthermore, excellent anti-interference, stability, and reproducibility were also presented by this modified electrode.     

Covalent modification of glassy carbon electrode with aspartic acid for simultaneous determination of hydroquinone and catechol

Glassy carbon electrode (GCE) is covalently modified with aspartic acid (Asp). The modified electrode is used for the simultaneous electrochemical determination of hydroquinone (HQ) and catechol (CC) and shows an excellent electrocatalytical effect on the oxidation of HQ and CC by cyclic voltammetry (CV) in 0.1 mol/L acetate buffer solution (pH 4.5). In differential pulse voltammetric (DPV) measurements, the modified electrode could separate the oxidation peak potentials of HQ and CC present in binary mixtures by about 101 mV though the bare electrode gave a single broad response. A successful elimination of the fouling effect by the oxidized product of HQ on the response of CC has been achieved at the modified electrode. The determination limit of HQ in the presence of 0.1 mmol/L CC was 9.0 x 10(-7) mol/L and the determination limit of CC in the presence of 0.1 mmol/L HQ was 5.0 x 10(-7) mol/L. The proposed method has been applied to the simultaneous determination of HQ and CC in a water sample with simplicity and high selectivity.     

A sensor based on the carbon nanotubes-ionic liquid composite for simultaneous determination of hydroquinone and catechol

MWNTs-IL-Gel/GCE, a glassy carbon electrode modified with multiwalled carbon nanotubes (MWNTs) and ionic liquids (IL), was developed to serve as a sensor for simultaneous determination of Hydroquinone (HQ) and catechol (CC) in this paper. The modified GCE showed two well-defined redox waves for HQ and CC in both CV and DPV with a peak potential separation of ca. 0.1 V, which was large enough for simultaneous detection. The results revealed that the oxidation of HQ and CC with the enhancement of the redox peak current and the decrease of the peak-to-peak separation exhibit excellent electrocatalytic behaviors. A high sensitivity of 1.8×10(-7)M with detection limits of 6.7×10(-8)M and 6.0×10(-8)M (S/N=3) for HQ and CC were obtained. Moreover, the constants of apparent electron transfer rate of HQ and CC at MWNTs-IL-Gel/GCE were calculated as 7.402 s(-1) and 8.179 s(-1), respectively, and the adsorption quantity of HQ and CC was 1.408×10(-6) mol cm(-2) with chronocoulometry. The developed sensor can be applied to determinate directly of HQ and CC in aqueous solution.     

Graphene Nanocomposites Based Electrochemical Sensing Platform for Simultaneous Detection of Multi-drugs

Three reduced graphene oxide nanocomposites were employed to achieve the simultaneous electrochemical determination of multi-drugs including acetaminophen (ACTM), carbendazim (CB) and ciprofloxacin (CFX). All nanocomposite modified electrodes showed improved current responses for three drugs. Notably cauliflower-like platinum nanoparticles decorated reduced graphene oxide modified electrode (or Pt−RGO/GCE) exhibited the best performance in terms of electrochemical stability. Using Pt−RGO/GCE, the linear detect ranges of 30–120 μM, 25–115 μM and 10–25 μM, and detection limit values of 3.49, 2.96, and 1.53 μM were achieved for ACTM, CB and CFX respectively. The electrode was further used for the successful determination of above drugs in tap and river water using differential pulse voltammetry. From the obtained results, we believe that Pt-RGO/GCE is highly promising for the fabrication of robust electrochemical sensors for simultaneously determining ACTM, CB and CFX or similar types of drugs in the future.     

Simultaneous determination of hydroquinone and catechol using a glassy carbon electrode modified with gold nanoparticles,ZnS/NiS@ZnS quantum dots and L-cysteine

We describe an electrochemical sensor for simultaneous determination of hydroquinone (HQ) and catechol (CC). A glassy carbon electrode (GCE) was modified with gold nanoparticles, L-cysteine, and ZnS/NiS@ZnS quantum dots using a layer-by-layer technique. The materials were characterized by X-ray diffractometry, field emission scanning electron microscopy, and electrochemical impedance and Fourier transform infrared spectroscopy. Cyclic voltammetry and differential pulse voltammetry revealed this modified GCE to represent a highly sensitive sensor for the simultaneous determination of HQ and CC. The anodic peak current for HQ at a working voltage of 80 mV (vs. Ag/AgCl) is related to its concentration in the 0.1 to 300 μM range (even in the presence of 0.1 mM of CC). The anodic peak current for CC at a working voltage of 184 mV is related to its concentration in the 0.5 to 400 μM range (even in the presence of 0.1 mM of HQ). The detection limits (at an S/N ratio of 3) are 24 and 71 nM for HQ and CC, respectively. The modified GCE was successfully applied to the determination of HQ and CC in aqueous solutions and gave satisfactory results.

A glassy carbon electrode was modified with gold nanoparticles, ZnS/NiS@ZnS quantum dots and L-cysteine and used for simultaneous determination of hydroquinone and catechol.

     

A Facile Fabrication of Poly-ethionine Film on Glassy Carbon Electrode for Simultaneous and Sensitive Detection of Dopamine and Paracetamol

An electrochemical sensor based on poly-ethionine (Poly-ET) film modified glassy carbon electrode was developed for sensitive and simultaneous sensing of dopamine (DA) and paracetamol (PA). The electropolymerization of ethionine monomer was carried out to modify the electrode. The modified electrode was characterized by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The Poly-ET/GCE exhibited excellent electrocatalysis towards the sensing of DA and PA. Poly-ET/GCE showed a linear increase of current response with increase concentration of DA and PA ranging from 0.1 μM–60 μM and 0.1 μM–180 μM, respectively. The LODs were found to be 7 nM and 18 nM (S/N=3) for DA and PA, respectively. This electrochemical sensor was successfully utilized for the detection of DA and PA in pharmaceutical samples.     

Simultaneous Determination of Dihydroxybenzene Isomers Using Preanodized Inlaying Ultrathin Carbon Paste Electrode

In this paper, we described a rapid, sensitive and selective method for simultaneous voltammetric determination of dihydroxybenzene isomers with a preanodized inlaying ultrathin carbon paste electrode (PAIUCPE). Scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS) and voltammetry were employed to characterize the configuration and electrochemical properties of the electrode. The resulting PAIUCPE exhibited excellent recognition ability towards dihydroxybenzene isomers. Three well‐defined oxidation peaks of catechol (CC), resorcinol (RC) and hydroquinone (HQ) can be identified entirely at the electrode. The oxidation peak potential difference between HQ and CC was 120 mV, CC and RC 430 mV, respectively. The peak currents increased linearly with increasing the concentration of dihydroxybenzene isomers. The proposed electrode can be applied to simultaneous determination of dihydroxybenzene isomers without previous chemical or physical separations.     

RNA Modified Electrodes for Simultaneous Determination of Dopamine and Uric Acid in the Presence of High Amounts of Ascorbic Acid

A promising electrochemical biosensor was fabricated by electrochemical grafting of ribonucleic acid (RNA) at 1.8 V (vs. SCE) on glassy carbon electrode (GCE) (denoted as RNA/GCE), for simultaneous detection of dopamine (DA) and uric acid (UA) with coexistence of excess amount of ascorbic acid (AA). The electrode was characterized by X‐ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The RNA modified layer on GCE exhibited superior catalytic ability and anionic exclusive ability in comparison with the DNA modified electrode. Three separated anodic DPV peaks were obtained at 0.312, 0.168 and ?0.016 V for UA, DA and AA, respectively, at the RNA/GCE in pH 7.0 PBS. In the presence of 2.0 mM AA, a linear range of 0.37 to 36 μM with a detection limit of 0.2 μM for DA, and in the range of 0.74 to 73 μM with a detection limit of 0.36 μM for UA were obtained. The co‐existence of 5000 fold AA did not interfere with the detection of DA or UA. The modified electrode shows excellent selectivity, good sensitivity and good stability.     

石墨烯/铁氰化钴复合膜修饰玻碳电极同时测定对苯二酚、邻苯二酚和间苯二酚

采用滴涂法和电沉积法制备了石墨烯/铁氰化钴复合膜修饰玻碳电极. 用扫描电镜对该纳米复合膜进行了表征.用循环伏安法研究了对苯二酚(HQ)、邻苯二酚(CT)和间苯二酚(RS)在修饰电极上的电化学行为. 实验结果表明, 相对于裸玻碳电极和石墨烯修饰电极, HQ, CT 和RS 在石墨烯/铁氰化钴修饰电极上的氧化峰电流显著提高. 利用差分脉冲伏安法测定, HQ, CT 和RS 分别在1.0×10^－6～1.5×10^－4 mol/L, 1.0×10^－6～2.0×10^－4 mol/L 和3.5×10^－6～2.5×10^－4 mol/L浓度范围内与氧化峰电流呈良好的线性关系, 相关系数分别为0.991, 0.993 和0.992. 信噪比为3 时, HQ, CT 和RS 检出限分别为2.0×10^－7, 2.1×10^－7 和3.5×10^－7 mol/L. 将该方法用于水样分析, 回收率为95.6%～106.1%.     

CuO Nanostructures Based Electrochemical Sensor for Simultaneous Determination of Hydroquinone and Ascorbic Acid

A simple, sensitive and reliable electrochemical sensor has been developed based on CuO nanostructures modified glassy carbon electrode for simultaneous determination of hydroquinone (HQ) and ascorbic acid (AA). The CuO nano material was synthesized by aqueous chemical growth method using different sources of OH. The characterization of nano material was performed by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy and energy dispersive X‐ray spectroscopy. The glassy carbon electrode was modified by CuO nano material using drop cast method and studied by cyclic voltammetry. The CuO/GCE exhibited excellent electrocatalytic activity towards the oxidations of HQ and AA in borate buffer solution (pH 8.0) and the corresponding electrochemical signals have appeared as two well resolved oxidation peaks with significant peak potential differences of (0.21V vs. Ag/AgCl). Differential pulse voltammetry was used for simultaneous determination of HQ and AA using the CuO/GCE. At the optimum conditions, for simultaneous determination by synchronous change of the analyte concentrations, the linear response ranges were between 0.0003–0.355 mM for HQ and 0.0001–0.30 mM for AA respectively. Furthermore, CuO/GCE was successfully applied for the independent determination of AA in fruit juices as well as for the simultaneous determination of HQ and AA in cosmetic samples.     

Simultaneous determination of catechol and hydroquinone based on poly (diallyldimethylammonium chloride) functionalized graphene-modified glassy carbon electrode

Simultaneous determination of catechol (CC) and hydroquinone (HQ) were investigated by voltammetry based on glassy carbon electrode (GCE) modified by poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene (PDDA-G). The modified electrode showed excellent sensitivity and selectivity properties for the two dihydroxybenzene isomers. In 0.1 mol/L phosphate buffer solution (PBS, pH 7.0), the oxidation peak potential difference between CC and HQ was 108 mV, and the peaks on the PDDA-G/GCE were three times as high as the ones on graphene-modified glass carbon electrode. Under optimized conditions, the PDDA-G/GCE showed wide linear behaviors in the range of 1 × 10⁻⁶−4 × 10⁻⁴ mol/L for CC and 1 × 10⁻⁶−5 × 10⁻⁴ mol/L for HQ, with the detection limits 2.0 × 10⁻⁷ mol/L for CC and 2.5 × 10⁻⁷ mol/L for HQ (S/N = 3) in mixture, respectively. Some kinetic parameters, such as the electron transfer number (n), charge transfer coefficient (α), and the apparent heterogeneous electron transfer rate constant (k _s), were calculated. The proposed method was applied to simultaneous determine CC and HQ in real water samples of Yellow River with satisfactory results.     

A graphene-based electrochemical sensor for sensitive and selective determination of hydroquinone

Graphene was prepared by electrochemical reduction of exfoliated graphite oxide at cathodic potentials, and used to fabricate a graphene-modified glassy carbon electrode (GCE) which was applied in a sensor for highly sensitive and selective voltammetric determination of hydroquinone (HQ). Compared to a bare (conventional) GCE, the redox peak current for HQ in pH 5.7 acetate buffer solution is significantly increased, indicating that graphene possesses electrocatalytic activity towards HQ. In addition, the peak-to-peak separation is significantly improved. The modified electrode enables sensing of HQ without interference by catechol or resorcinol. Under optimal conditions, the sensor exhibits excellent performance for detecting HQ with a detection limit of 0.8?μM, a reproducibility of 2.5% (expressed as the RSD), and a recoveries from 98.4 to 101.2%.

A Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotube/Chitosan Composite as a New Sensor for Simultaneous Determination of Acetaminophen and Mefenamic Acid in Pharmaceutical Preparations and Biological Samples

A new chemically modified electrode is constructed based on multiwalled carbon nanotube/chitosan modified glassy carbon electrode (MWCNTs‐CHT/GCE) for simultaneous determination of acetaminophen (ACT) and mefenamic acid (MEF) in aqueous buffered media. The measurements were carried out by application of differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA) methods. Application of DPV method showed that the linear relationship between oxidation peak current and concentration of ACT and MEF were 1 μM to 145 μM, and 4 μM to 200 μM, respectively. The analytical performance of this sensor has been evaluated for detection of ACT and MEF in human serum, human urine and a pharmaceutical preparation with satisfactory results.     

Simultaneous determination of hydroquinone and catechol based on glassy carbon electrode modified with gold-graphene nanocomposite

We have synthesized a virtually monodisperse gold-graphene (Au-G) nanocomposite by a single-step chemical reduction method in aqueous dimethylformamide solution. The nanoparticles are homogenously distributed over graphene nanosheets. A glassy carbon electrode was modified with this nanocomposite and displayed high electrocatalytic activity and extraordinary electronic transport properties due to its large surface area. It enabled the simultaneous determination of hydroquinone (HQ) and catechol (CC) in acetate buffer solution of pH?4.5. Two pairs of well-defined, quasi-reversible redox peaks are obtained, one for HQ and its oxidized form, with a 43 mV separation of peak potentials (ΔE_p), the other for CC and its oxidized form, with a ΔE_p of 39 mV. Due to the large separation of oxidation peak potentials (102 mV), the concentrations of HQ and CC can be easily determined simultaneously. The oxidation peak currents for both HQ and CC increase linearly with the respective concentrations in the 1.0 μM to 0.1 mM concentration range, with the detection limits of 0.2 and 0.15 μM (S/N?=?3), respectively. The modified electrode was successfully applied to the simultaneous determination of HQ and CC in spiked tap water, demonstrating that the Au-G nanocomposite may act as a high-performance sensing material in the selective detection of some environmental pollutants.

Electrochemical Sensing Platform Based on Lotus Stem-derived Porous Carbon for the Simultaneous Determination of Hydroquinone,Catechol and Nitrite

A simple and highly selective electrochemical sensor based on carbonized lotus stem (CLS) was developed for the simultaneous determination of hydroquinone (HQ), catechol (CC), and nitrite (NT) by using cyclic voltammetry (CV) and amperometry (AMP) methods. The CLS was characterized by the methods including field emission scanning electron microscopy (FE-SEM), Raman spectrum, FT-IR spectrum and X-ray diffraction (XRD). Brunauer-Emmett-Teller (BET) method was used to evaluate the pore structure and surface area of CLS. The oxidation peaks for HQ (116.2 mV), CC (220.1 mV), and NT (818.9 mV) were well separated under optimized conditions, which improved their simultaneous determination. The CLS modified electrode showed a good linear range between 1.0×10 ⁻⁶ to 7.0×10 ⁻⁴ M for HQ, and the detection limit was calculated as 0.15 μM. For CC the linear relationship was 1.0×10 ⁻⁶ to 3.0×10 ⁻³ M with the detection limit of 0.11 μM. For NT the linear relationship was 5.0×10 ⁻⁷ to 4.0×10 ⁻³ M with the detection limit of 0.09 μM. The results indicated that the intrinsic structure of natural biomass can be expected to design porous carbon for electrochemical sensors.