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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]

• 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]