Search

In the present paper, the electrochemical reduction of nitrite at a hemoglobin modified pencil lead electrode (Hb/PLE) is described. The electrochemical properties of nitrite were studied by cyclic voltammetry and chronoamperometry. Results showed that the hemoglobin film has an excellent electrochemical activity towards the reduction of nitrite. By using voltammetric and chronoamperometric methods, α, n α and n were calculated. Then the ability of the electrode for nitrite determination was investigated using differential pulse voltammetry. The electrocatalytic reduction peak currents were found to be linear with the nitrite concentration in the range from 10 to 220 µM with a detection limit of 5 µM. The relative standard deviation is 2 % for 3 successive determinations of a 100 µM nitrite solution. This modified electrode was successfully used for the detection of low amounts of NO2− in spinach sample and a spiked sample of tap water. [ABSTRACT FROM AUTHOR]

In the present paper simultaneous determination of nitrite and hydrogen peroxide using hemoglobin modified pencil lead electrode (Hb/PLE) prepared by a simple and rapid electroless method was described. In the first part of the work the reduction of NO2 and H2O2 at the modified electrode was investigated by cyclic voltammetry. Then under optimal conditions using differential pulse voltammetry, the biosensor could be used for the determination of H2O2 at concentration ranging from 5 to 240 M and NO2 at concentration ranging from 10 to 240 M. The detection limits were 3×10−6 and 5×10−6 M, for NO2 and H2O2 respectively. Differential pulse voltammetry also used for the simultaneous determination of NO2 and H2O2. This modified electrode successfully used for the determination of NO2 and H2O2 in tap water and mother's milk samples. [ABSTRACT FROM AUTHOR]

A simple and cost‐effective electrochemical sensor was developed for the determination of very low amounts of vanillin in various foodstuffs. Multi‐walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE) beside differential pulse voltammetry (DPV) was applied for the measurement of vanillin. The effect of several variables on the voltammetric sensing of the vanillin, such as pH, buffer type and concentration, and the amount of MWCNTs were investigated. Using the optimized condition, the proposed sensor can detect vanillin in the concentration range from 4.15 to 294.12 µM with a correlation coefficient of 0.999, while the limit of detection is calculated to be 3.44 µM. Furthermore, to improve the detection sensitivity and detection of sub‐micromolar levels of vanillin, the capability of the Adsorptive stripping differential pulse voltammetry (AdSDPV) technique was also studied. The detection limit improved to 8.51 nM using the stripping method. The developed sensor was successfully utilized for the determination of vanillin in some food samples such as ice cream and cake with desirable accuracy and recovery. Due to its simplicity and ability to detection of trace amounts, the proposed sensor can be easily used in quality control labs and industry tests to measure vanillin. Novelty impact statement: Despite various methods reported on measuring vanillin, the proposed electrochemical sensor is very simple, cost‐effective, and fast. This method can measure vanillin in a wide variety of foodstuffs with a lower limit of detection and is less prone to interferences from other possible compounds. Because of its simplicity and ability to detect trace amounts (nano‐molar LOD), the proposed sensor has the capability of using in quality control laboratories and industrial tests for measuring vanillin. [ABSTRACT FROM AUTHOR]

Abstract: An electrochemically pretreated pencil graphite electrode (PGE) has been proposed for simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of high levels of ascorbic acid (AA). The electrochemical pretreatment of PGE was achieved in phosphate buffer (pH 7) by the potential recycling between 1.5–2.0V/SCE for 100 cycles, and at the scan rate of 100mVs−1. The influence of electrochemical pretreatment of PGE on the separation of overlapped peaks of AA, DA and UA were studied and optimum conditions were suggested. Differential pulse voltammetry (DPV) was used for simultaneous determination of DA and UA in the presence of high concentrations of AA. The peak separation between DA and AA, and also between DA and UA was up to 260 and 160mV, respectively. The calibration curves were in the range of 0.15–15μM and 0.3–150μM for DA and UA in the presence of AA, respectively. The detection limits (S/N=3) were 0.033 and 0.12μM for DA and UA, respectively. The results reveal that pretreatment of the pencil graphite electrode surface not only improves its electrochemical catalytic activities towards the oxidation of DA and UA, but also resolves the overlapped oxidation peaks of AA, DA and UA into three well-defined peaks. The present method can apply for UA and DA determination in human serum and urine, and also for some commercial pharmaceutical samples without additional sample pre-treatment. [Copyright &y& Elsevier]

In the present work, the aluminum electrode surface was modified with a thin layer of palladium by dipping its polished surface in a 25% ammonia solution of PdCl2. The electrocatalytic ability of the modified electrode towards the paracetamol (PCT), ascorbic acid (AA), and codeine (CO) oxidation was investigated using cyclic voltammetry, chronoamperometry. The number of electrons for rate-determining step and diffusion coefficient of PCT, AA, and CO were determined. The electro-oxidation pathway and kinetics, including transfer coefficient α and diffusion coefficient D, are estimated. The results indicated that the simultaneous voltammetry of the three compounds was possible in a mixture solution. [ABSTRACT FROM AUTHOR]

• Utilization of activated pencil lead electrode (APLE) for the first time in determination of gallic acid in food stuffs. • High catalytic activity of the APLE toward gallic acid oxidation. • Selective determination of gallic acid in the presence of high levels of ascorbic acid in the food stuffs using APLE. • Determination of gallic acid in sub-micromolar concentration range via adsorptive stripping (AdSDPV) using APLE. An electrochemical sensor for the determination of some polyphenolic compounds such as Gallic acid (GA) and Galloyl esters was developed using the activated pencil lead electrode (APLE). At first, a study has been made of the optimum conditions for electrochemical activation of the pencil lead electrode. Potentiodynamic and potentiostatic strategies were investigated for activation of the pencil lead electrode and the results show that the potentiodynamic pretreatment gives better performance toward measurement of the polyphenolic compounds. Electrochemical properties of GA were investigated using chronoamperometry and cyclic voltammetry; and some thermodynamic and kinetic variables such as α, n α , and D were calculated. Sensitive differential pulse voltammetry (DPV) technique was applied for the determination of Gallic acid and Galloyl esters in different samples. Enhanced oxidation peak currents of Gallic acid were observed at APLE when compared with non-activated PLE. The calibration graph has two linear ranges of 0.49–24.3 µM and 0.07–0.83 mM, and the obtained limit of detection for S/N = 3 was 0.25 µM. Adsorptive stripping differential pulse voltammetry (AdSDPV) was also conducted to determine Gallic acid and Galloyl esters in sub-micromolar concentration range. Using the AdSDPV method, the limit of detection was improved and calculated to be 5.2 nM. The proposed method was successfully applied for quantification of the total concentration of Gallic acid and Galloyl esters in a variety of real samples such as black and green tea, and mango juice samples, and desirable recovery values indicated the good accuracy of the developed sensor. [ABSTRACT FROM AUTHOR]