Simultaneous Determination of Hydroquinone and Catechol by Differential Alternative Pulses Voltammetry

The second order voltammetric technique of high resolution, Differential Alternative Pulses Voltammetry (DAPV), was applied for the simultaneous determination of hydroquinone (HQ) and catechol (CC) on bare spectroscopic graphite electrode. Well resolved anodic and cathodic peaks situated on both sides of the zero line were obtained, while the differential pulse voltammograms were overlapped. The linear concentration range for HQ and CC quantification by DAPV was extended up to 20 μmol L⁻¹ for both the isomers. The sensitivity of the determination was found to be 6.00 μA L μmol⁻¹ and 3.61 μA L μmol⁻¹, while the limit of detection reached was 0.2 μmol L⁻¹ and 0.5 μmol L⁻¹ for HQ and CC, respectively. No interference was observed from the commonly coexisting organic species such as resorcinol, phenol and p‐benzoquinone. The great resolution power of DAPV permitted obtaining excellent results without any electrode modification and any mathematical data processing.     

Application of Anodic Stripping Differential Alternative Pulses Voltammetry for Simultaneous Species Quantification

The second order voltammetric technique Differential Alternative Pulses Voltammetry (DAPV) was applied in anodic stripping mode for simultaneous quantification of traces of species having close E_1/2. The potential‐time waveform and the signal processing allowing the DAPV application in stripping mode are presented. The pulses widths and amplitudes were optimized to obtain maximal sensitivity and resolution at traces of In³⁺ and Cd²⁺ (having E_1/2 difference of 45 mV) simultaneous quantification in presence of excess of Pb²⁺. Precise results for both species concentrations were obtained up to In³⁺ to Cd²⁺ concentration ratio as high as 1 to 10 without any sample pre‐treatment in purified industrial waste waters using 0.1 mol L⁻¹ HCl as supporting electrolyte.     

Silver Nanoparticles‐Silsesquioxane Nanomaterial Applied to the Determination of 4‐Nitrophenol as a Biomarker

A novel silsesquioxane material was synthetized and used as a stabilizing agent for silver nanoparticles. This hybrid material was characterized by FTIR, ²⁹Si CP‐MAS NMR, ¹³C DEPT 135° NMR and TGA techniques and the silver nanoparticles were characterized from DLS, UV‐Vis spectroscopy, zeta‐potential, TEM and SAXS results. The silver nanoparticles obtained were spherical in shape with a diameter of 3.74 nm. The nanomaterial was successfully applied in the modification of a glassy carbon electrode and a pronounced current response was obtained in the determination of the biomarker 4‐nitrophenol. Quantum chemical calculations, using density functional theory, were also performed in order to evaluate the redox properties of the analyte. Two different linear ranges were obtained applying optimal square wave voltammetry conditions. The reduction peak currents obtained were linear for 4‐NP concentrations in the ranges of 0.29 to 1.50 μmol L^?1 (E_d=?0.6 V and t_d=20 s) and 2.75 to 31.5 μmol L^?1, with a theoretical (signal to noise=3) limit of detection of 0.05 μmol L^?1 (t_d=20 s). The proposed method was successfully applied to the determination of 4‐NP in synthetic serum samples at different levels of 4‐NP with a recovery range of 94–101 %. Validation was performed using a comparative method through the capillary electrophoresis (CE) technique.     

Cathodic Electrochemical Detection of Nitrophenols at a Bismuth Film Electrode for Use in Flow Analysis

The bismuth film electrode (BiFE) is presented for use in both batch voltammetric and flow injection (FI) amperometric detection of some nitrophenols (2‐nitrophenol, 2‐NP; 4‐nitrophenol, 4‐NP; 2,4‐dinitrophenol, 2,4‐DNP). The bismuth film was deposited ex situ (batch measurements) and in‐line (FI) onto a glassy carbon substrate electrode. Batch analysis of the nitrophenols was carried out in 0.04 M Britton Robinson (BR) buffer pH 4, while for FI measurements, a carrier/electrolyte solution composed of 0.1 M BR buffer pH 4 mixed with methanol (20+80, v/v%) was employed to resemble media used in preconcentration/clean‐up and flow separation sample pretreatment procedures. Under batch conditions, the voltammetric behavior of the nitrophenols was examined for dependence on medium pH in the range of 2 to 10. Employing the square‐wave voltammetry mode, the limits of detection were 0.4 μg L^?1, 1.4 μg L^?1, and 3.3 μg L^?1 for 2‐NP, 4‐NP, and 2,4‐DNP, respectively. Under flow conditions, a simple in‐line electrochemical bismuth film renewal procedure was tested and shown to provide very good inter‐ and intra‐electrode reproducibility of the current signals at low μg L^?1 analyte concentrations. The limits of detection for 2‐NP, 4‐NP and 2,4‐DNP obtained using FI and amperometric detection at ?1.0 V (vs. Ag/AgCl) were 0.3 μg L^?1, 0.6 μg L^?1 and 0.7 μg L^?1, respectively, with linear ranges extending up to 20 μg L^?1. The attractive performance of the BiFE under flow analysis conditions offers great promise with respect to its detection capability and to its use for a prolonged period of time with no need for inconvenient removal of the electrode from the system for mechanical surface treatment.     

Electrochemical Determination of Neurotransmitters at Crown Ether Modified Carbon Nanotube Composite: Application for Sub‐nano‐sensing of Serotonin in Human Serum

We propose an electrochemical sensor based on applying two successive thin layers from a mixture of multiwalled carbon nanotubes‐ionic liquid crystal and crown ether at glassy carbon electrode surface (GC/(CNTs‐ILC)/Crown). The sensor was used for sensitive determination of neurotransmitters based on effective synergism between its components. The compact conducting surface of (CNTs ‐ ILC) with large surface area allowed the assembling of stable host‐guest inclusion complexes between crown ethers and neurotransmitters. The GC/(CNTs‐ILC)/Crown exhibited excellent electro‐catalytic activity toward the determination of serotonin (ST) in a wide linear dynamic range: 0.005 μmol L^?1 to 100 μmol L^?1. In the concentration range 0.005 μmol L^?1 to 1 μmol L^?1, the detection limit is 2.03×10^?10 mol L^?1 and quantification limit is 6.78×10^?10 mol L^?1 with correlation coefficient 0.999. The sensor was successfully applied for ST detection in human serum samples with satisfied recovery results. The sensor showed excellent analytical performance for the determination of ST in terms of low detection limit, good sensitivity and reproducibility. Furthermore excellent anti‐interference ability and simultaneous determination of ST in presence of other compounds as ascorbic acid, dopamine and antidepressant drug were achieved.     

A Simple Approach to Simultaneous Electroanalytical Quantification of Acetaminophen and Tramadol Using a Boron‐doped Diamond Electrode in the Existence of Sodium Dodecyl Sulfate

The present work describes the individual, selective and simultaneous quantification of acetaminophen (ACP) and tramadol hydrochloride (TRA) using a modification‐free boron‐doped diamond (BDD) electrode. Cyclic voltammetric measurements revealed that the profile of the binary mixtures of ACP and TRA were manifested by two irreversible oxidation peaks at about +1.04 V (for ACP) and +1.61 V (for TRA) in Britton‐Robinson (BR) buffer pH 3.0. TRA oxidation peak was significantly improved in the presence of anionic surfactant, sodium dodecyl sulfate (SDS), while ACP signal did not change. By employing square‐wave stripping mode in BR buffer pH 3.0 containing 8×10^?4 mol L^?1 SDS after 30 s accumulation under open‐circuit voltage, the BDD electrode could be used for quantification of ACP and TRA simultaneously in the ranges 1.0–70 μg mL^?1 (6.6×10^?6–4.6×10^?4 mol L^?1) and 1.0–70 μg mL^?1 (3.3×10^?6–2.3×10^?4 mol L^?1), with detection limits of 0.11 μg mL^?1 (7.3×10^?7 mol L^?1) and 0.13 μg mL^?1 (4.3×10^?7 mol L^?1), respectively. The practical applicability of the proposed approach was tested for the individual and simultaneous quantification of ACP and/or TRA in the pharmaceutical dosage forms.     

Differential Pulse Voltammetric Determination of 2‐Methyl‐4,6‐Dinitrophenol using Bismuth Bulk Electrode

This work reports the application of bismuth bulk electrode (BiBE) for the determination of 2‐methyl‐4,6‐dinitrophenol (MDNP) by differential pulse voltammetry (DPV) in Britton‐Robinson buffer of pH 12.0 as an optimal medium. BiBE was prepared by transferring molten bismuth into a glass tube under constant stream of nitrogen. The linear concentration dependences were measured from 1 to 10 μmol ? L^?1 and from 10 to 100 μmol ? L^?1 by using optimum accumulation potential of ?0.7 V and optimum accumulation time 30 s. Under these conditions limit of determination and limit of quantification was 0.45 and 1.5 μmol ? L^?1, respectively. The developed method was successfully applied for the analysis of tap water as a model sample.     

A Sensitive Sensor Based on Single‐walled Carbon Nanotubes: Its Preparation,Characterization and Application in the Electrochemical Determination of Drug Clorsulon in Milk Samples

Within this paper, a glassy carbon electrode modified with single‐walled carbon nanotubes (SWCNTs?GCE) was prepared, and employed for the determination of clorsulon (Clo), which is a frequently used veterinary drug against common liver fluke. The comprehensive topographical and electrochemical characterizations of bare GCE and SWCNTs?GCE were performed by atomic force microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. Significantly enhanced electrochemical characteristics of SWCNTs?GCE toward a ferrocyanide/ferricyanide redox couple was observed when compared to bare GCE. Further, the prepared sensor was applied for the voltammetric determination of Clo, which was electrochemically investigated for the first time in this work. Voltammetric experiments were performed using square‐wave voltammetry with optimized parameters in phosphate buffer solution, pH 6.8, which was selected as the most suitable medium for the determination of Clo. The corresponding current at approx. +1.1 V increased linearly with Clo concentration within two linear dynamic ranges of 0.75–4.00 μmol L^?1 (R²=0.9934) and 4.00–15.00 μmol L^?1 (R²=0.9942) with a sensitivity for the first calibration range of 0.76 μA L μmol^?1, a limit of detection of 0.19 μmol L^?1, and a limit of quantification of 0.64 μmol L^?1. The developed method was subsequently applied for quantitative analysis of Clo in milk samples with results proving high repeatability and recovery.     

Determination of three Tumor Biomarkers (Homovanillic Acid,Vanillylmandelic Acid,and 5‐Hydroxyindole‐3‐Acetic Acid) Using Flow Injection Analysis with Amperometric Detection

Flow injection analysis with amperometric detection (FIA‐AD) at screen‐printed carbon electrodes (SPCEs) in optimum medium of Britton‐Robinson buffer (0.04 mol ? L^?1, pH 2.0) was used for the determination of three tumor biomarkers (homovanillic acid (HVA), vanillylmandelic acid (VMA), and 5‐hydroxyindole‐3‐acetic acid (5‐HIAA)). Dependences of the peak current on the concentration of biomarkers were linear in the whole tested concentration range from 0.05 to 100 μmol ? L^?1, with limits of detection (LODs) of 0.065 μmol ? L^?1 for HVA, 0.053 μmol ? L^?1 for VMA, and 0.033 μmol ? L^?1 for 5‐HIAA (calculated from peak heights), and 0.024 μmol ? L^?1 for HVA, 0.020 μmol ? L^?1 for VMA, and 0.012 μmol ? L^?1 for 5‐HIAA (calculated from peak areas), respectively.     

Effect of Different Carbon Blacks on the Simultaneous Electroanalysis of Drugs as Water Contaminants Based on Screen‐printed Sensors

For the construction of the sensor, three different carbon black (CB) materials (VULCAN XC72R, BLACK PEARLS 4750 and CB N220) were explored as modifying nanomaterial. Firstly, the electrochemical activity of the each SPE modified was compared by cyclic voltammetry and electrochemical impedance spectroscopy technique, using [Fe(CN)₆]^3?/4? as redox couple. After demonstrating that electrodes modified with different types of CB were characterized by improved electrochemical performances when compared with bare electrodes, and among them, electrodes modified with CB BP4750 is characterised by slightly better electrochemical properties, this type of electrode was used for the development of the analytical method. By applying SWV technique in 0.2 mol L^?1 phosphate buffer (pH 3.0), the obtained analytical curves for ACP and LVF were found linearly from 4.0 to 80.0 μmol L^?1 and from 0.90 to 70.0 μmol L^?1 with limit of detection of 2.6 μmol L^?1 and 0.42 μmol L^?1 for ACP and LVF, respectively. Finally, the quantification of these drugs in river water was evaluated using the new here‐proposed sensor by recovery method in spiked samples, obtaining satisfactory recovery values. The results achieved demonstrated that the developed analytical tool is of great analytical interest being easy to use, cost‐effective, miniaturized, and thus suitable for low cost on site analysis.     

Direct Simultaneous Determination of α‐ and β‐Naphthol Isomers at GC‐Electrode Modified with CNTs Network Joined by Pt Nanoparticles Through Derivative Voltammetry

The semi‐derivative technique was adopted to improve the resolution and surfactant was added to sample solution to enhance the sensitivity, α‐ and β‐naphthol isomers could be determined directly and simultaneously at glassy carbon electrode modified with carbon nanotubes network joined by Pt nanoparticles. In 0.1 mol L^?1 HAc‐NaAc buffer solution (pH 5.8), the linear calibration ranges were 1.0×10^?6 to 8.0×10^?4 mol L^?1 for both α‐ and β‐naphthols, with detection limits of 5.0×10^?7 for α‐ and 6.0×10^?7 mol L^?1 for β‐naphthol. The amount of naphthol isomers in artificial wastewater has been tested with above method, and the recovery was from 98% to 103%.     

Alternating Layers of Iron(III) Tetra(N‐methyl‐4‐pyridyl)‐porphyrin and Copper Tetrasulfonated Phthalocyanine for Amperometric Detection of 4‐Nitrophenol in Nanomolar Levels

The present work describes the development of a highly sensitive amperometric sensor for 4‐NP in nanomolar levels using a glassy carbon electrode modified with alternating layers of CuTSPc and FeT4MPyP. After optimizing the operational conditions, the sensor provided a linear response range for 4‐NP from 5 up to 100 nmol L^?1 with sensitivity, detection, and quantification limits of 14 nA L nmol^?1, 1.9 nmol L^?1, and 5.4 nmol L^?1, respectively. The proposed sensor showed a stable response for at least 200 successive determinations. This modified electrode can be used to the determination of 4‐NP in water samples.     

Sensitive Voltammetric Determination of Bisphenol A Based on a Glassy Carbon Electrode Modified with Copper Oxide‐Zinc Oxide Decorated on Graphene Oxide

A highly sensitive and selective chemical sensor was prepared based on metallic copper‐copper oxides and zinc oxide decorated graphene oxide modified glassy carbon electrode (Cu?Zn/GO/GCE) through an easily electrochemical method for the quantification of bisphenol A (BPA). The composite electrode was characterized via scanning electron microscopy (SEM), X‐Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of BPA in Britton‐Robinson (BR) buffer solution (pH 7.1) was examined using cyclic voltammetry (CV). Under optimized conditions, the square wave voltammetry (SWV) response of Cu?Zn/GO/GCE towards BPA indicates two linear relationships within concentrations (3.0 nmol L^?1?0.1 μmol L^?1 and 0.35 μmol L^?1?20.0 μmol L^?) and has a low detection limit (0.88 nmol L^?1). The proposed electrochemical sensor based on Cu?Zn/GO/GCE is both time and cost effective, has good reproducibility, high selectivity as well as stability for BPA determination. The developed composite electrode was used to detect BPA in various samples including baby feeding bottle, pacifier, water bottle and food storage container and satisfactory results were obtained with high recoveries.     

Screen‐Printed Disposable Sensors Modified with Bismuth Precursors for Rapid Voltammetric Determination of 3 Ecotoxic Nitrophenols

This work reports the application of screen‐printed electrodes bulk‐modified with bismuth precursors to the voltammetric determination of 2‐nitrophenol (2‐NP), 4‐nitrophenol (4‐NP) and 2,4‐dinitrophenol (2,4‐DNP) in water samples. A bismuth film was formed at the electrode surface via in situ reduction of the precursor compound contained in the electrode matrix by cathodic polarization at ?1.20 V. The formation of bismuth layer at the precursor‐modified electrodes was assessed by cyclic voltammetric (CV) at different pH values and by optical techniques. The target nitrophenols were voltammetrically determined by recording their reduction peaks in the differential pulse (DP) mode. The composition and content of the precursor compounds in the printed ink and the effect of the pH of the supporting electrolyte on the DP reduction currents of the 3 target nitrophenols were studied. The limits of quantification (LOQs) in three water matrices (distilled water, tap water and surface water) were in the range 1.1–2.2 µmol L^?1_. Using a simple solid‐phase extraction (SPE) procedure with Lichrolut EN cartridges and elution with methanol, a preconcentration factor of 100 was achieved; the LOQs were 0.021, 0.027 and 0.025 µmol L^?1 for 2‐NP, 4‐NP and 2,4‐DNP, respectively. The recoveries of samples spiked with the 3 target nitrophenols at two concentration levels (0.04 and 0.1 µmol L^?1) were always >87 %.     

Electrochemical Sensing Platform Based on Nano‐Perovskite/Glycine/Carbon Composite for Amlodipine and Ascorbic Acid Drugs

People suffered from essential hypertension have increased oxidative stress. Thus, adding vitamin C to their medical therapy resulted in decreasing the oxidative stress and increasing the antioxidant status. This may prevent further vascular damage due to the oxidative stress, leading to a better diagnosis in critical hypertension patients. A novel sensor was fabricated based on NdFeO₃ nano‐perovskite/glycine/carbon nanotubes modified carbon paste electrode in presence of sodium dodecyl sulfate; GLNFCNTCP‐SDS for electrochemical sensing and simultaneous determination of antihypertensive and antioxidant drugs, Amlodipine (AML) and ascorbic acid. The developed nanocomposite showed interactive characteristics of all the modifiers as high conductivity, enhanced surface area, surface fouling resistance and stability. This leads to accelerated electron transfer rate and increased current response of electro‐oxidation of AML by 8.3 folds compared to unmodified electrode. The method validity was investigated successfully by the quantitative analysis of AML in human urine samples and Norvasc tablets with acceptable recovery results. The featured merits of the proposed composite in the analysis of AML in human urine samples were; wide concentration range of 0.003 μmol L^?1 to 200 μmol L^?1, sensitivity of 113.2 μA/μmol L^?1, detection limit of 0.704 nmol L^?1, and quantification limit of 2.35 nmol L^?1.     

Application of simultaneous separation and derivatization for the determination of α‐lipoic acid in urine samples by high‐performance liquid chromatography with spectrofluorimetric detection

To help to clarify therapeutic functions of lipoic acid (LA) in biochemical and clinical practice we have elaborated a fast, simple and accurate HPLC method enabling determination of LA in human urine. The proposed analytical approach includes reduction of LA with tris(2‐carboxyethyl)phosphine and simultaneous separation and derivatization of the analyte with butylamine and o‐phthaldialdehyde followed by spectrofluorimetric detection at λ_ex = 340 nm and λ_em = 440 nm. The assay was performed using gradient elution and the mobile phase containing 0.0025 mol L^?1 o‐phthaldialdehyde in 0.0025 mol L^?1 NaOH and acetonitrile. Linearity of the detector response for LA was observed in the range of 0.3–8 μmol L^?1. Limits of detection and quantification for LA in urine samples were 0.02 and 0.03 μmol L^?1, respectively. The total analysis time, including sample work‐up, was <20 min. The analytical procedure was successfully applied to analysis of real urine samples delivered from six healthy volunteers who received a single 100 mg dose of LA.     

Feasibility of a Nano‐Carbon Black Paste Electrode for Simultaneous Voltammetric Determination of Antioxidants in Food Samples and Biodiesel in the Presence of Surfactant

In this work, a simple and low‐cost method was developed for the simultaneous determination of the antioxidants tert‐butylhydroquinone (TBHQ) and butylated hydroxyanisole (BHA) in the presence of the cationic surfactant CPB by square wave voltammetry (SWV) technique using a carbon black paste electrode (CBPE). The performance of the method was investigated by varying parameters such as pH, electrolyte, and type and concentration of surfactant. Under the optimum conditions of 0.2 mol L^?1 phosphate buffer (pH 7.0), 600.0 μmol L^?1 of cetylpyridinium bromide surfactant and SWV operating parameters optimized through the Doehlert matrix, the method presented low limits of quantification for TBHQ and BHA (0.23 and 0.26 μmol L^?1, respectively) and high precision in successive measurements. The proposed method was applied in mayonnaise, margarine and biodiesel and the accuracy of method was checked by the HPLC technique.     

Pencil Graphite Electrode Decorated with Xylenol Orange Flakes for Studying Possible Pharmacokinetic Interaction Between Vardenafil and Daclatasvir

The main aim of the current work is to investigate possible pharmacokinetic interactions between vardenafil hydrochloride (VAR), which is used for the treatment of erectile dysfunction and daclatasvir dihydrochloride (DAC), which is used for the treatment of chronic hepatitis C viral infection when they are concomitantly administered. Therefore, a sensitive and selective square‐wave voltammetric method was developed and validated for simultaneous determination of VAR and DAC using disposable pencil graphite electrode (PGE) modified with xylenol orange (X.O.) flakes as an electrochemical sensor. A full investigation of the experimental parameters for obtaining the highest electroanalytical signal with sufficient resolution between the oxidation peaks of two compounds was performed. It was found that VAR and DAC were resolved on X.O./PGE with different potentials at 1.4 V and 0.9 V, respectively using Britton‐Robinson buffer (pH 2.2) and 0.1 mol L^?1 KCl as a supporting electrolyte. In addition, with the aid of cyclic voltammetry, a mechanistic scheme for the oxidation behaviour of both VAR and DAC was suggested. The proposed square wave voltammetric method was successfully applied for trace quantification of VAR and DAC in male rabbits. The suggested approach shows detection and quantification limits in rabbit plasma samples of 0.06 and 0.17 μmol L^?1, respectively for VAR and 0.13 and 0.39 μmol L^?1, respectively for DAC. The pharmacokinetic parameters of VAR alone and in combination with DAC after oral administration to rabbits were successfully estimated. The obtained results confirm that when DAC is co‐administered with VAR, plasma concentration of VAR increases, which necessitates dose adjustment for VAR to prevent toxicological consequences in patients.     

Electrogenerated Chemiluminescence of Tris(2,2′‐bipyridyl)ruthenium(II) Immobilized in Humic Acid‐Silica‐Poly(vinyl alcohol) Composite Films

In this paper, we report the first attempt to use humic acid (HA) as modifiers to prepare the organic‐inorganic hybrid modified glassy carbon electrodes based on HA‐silica‐PVA (poly(vinyl alcohol)) sol‐gel composite. Electroactive species of tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy) ) can easily incorporate into the HA‐silica‐PVA films to form Ru(bpy) modified electrodes. The amount of Ru(bpy) incorporated in the composite films strongly depends on the amount of HA in the hybrid sol. Electrochemical and electrogenerated chemiluminescence (ECL) of Ru(bpy) immobilized in HA‐silica composite films coated on a glassy carbon electrode have been studied with tripropylamine (TPA) as the coreactant. The analytical performance of this modified electrode was evaluated in a flow injection analysis (FIA) system with a homemade flow cell. The as‐prepared electrode showed good stability and high sensitivity. The detection limits (S/N=3) were 0.050 μmol L^?1 for TPA and 0.20 μmol L^?1 for oxalate, and the linear ranges were from 0.10 μmol L^?1 to 1.0 mmol L^?1 for TPA and from 1.0 μmol L^?1 to 1.0 mmol L^?1 for oxalate, respectively. The resulting electrodes were stable over two months.     

Sensitive Simultaneous Determination of o-Nitrophenol and p-Nitrophenol in Water by Surfactant-Mediated Differential Pulse Voltammetry

A simple, low-cost and sensitive electroanalytical method was developed for the simultaneous determination of p-nitrophenol and o-nitrophenol isomers in water samples at a glassy carbon electrode (CGE) in the presence of cationic surfactant. The electrochemical behavior of p-nitrophenol and o-nitrophenol was studied by cyclic voltammetry (CV) in 0.1?mol L^?1 acetate/acetic acid buffer (pH 3.70) in the presence and absence of cetylpyridinium bromide. The resolution of overlapped cathodic peaks potentials (E_pc) of isomers was successfully improved in the presence of 100.0?µmol L^?1 cetylpyridinium bromide, thus making this approach ideal for the simultaneous determination of isomers. Under the optimized conditions in 0.05?mol L^?1 HEPES buffer at pH 7.0 using differential pulse voltammetry (DPV) at a scan rate of 45?mV s^?1, pulse amplitude of 220?mV and modulation time of 10?ms, limits of detection 0.59?µmol L^?1 for p-nitrophenol and 1.14?µmol L^?1 for o-nitrophenol were obtained with linear ranges from 2.0 to 60.0?µmol L^?1 and 3.0 to 60.0?µmol L^?1, respectively. The intraday precision was assessed as relative standard deviation (%) for 20.0 and 40.0?µmol L^?1 concentrations were 4.30% and 2.41% for p-nitrophenol and 4.87% and 2.20% for o-nitrophenol, respectively. The developed method was applied for the determination of the isomers in lake water samples. The accuracy was attested by comparison with high-performance liquid chromatography with diode array detection (HPLC-DAD) as a reference analytical technique. Recovery values ranging from 90.3% to 111.8% also attested to the accuracy of method for analysis of real samples.