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In this study, the metoprolol (MTP), which is a beta-blocker class molecule used in hypertension treatment, was determined by modifying the glassy carbon electrode (GCE) with a molecular imprinting technique. Firstly, p-toluene sulfonic acid (PTSA) and aniline (AN) were co-electropolymerized in the presence of MTP as a template molecule on GCE and MTP contained poly(aniline-co-p-toluene sulfonic acid) (p(AN-co-PTSA)) film was obtained. Then, the template metoprolol molecule was desorbed from the conductive p(AN-co-PTSA) film structure on the GCE surface using hydrochloric acid. Obtained molecularly imprinted electrodes were used to determine MTP by the square wave voltammetry (SWV) method. The modified electrodes obtained showed a correlation coefficient (R²) of 0.9995 in the 40-1500 µM MTP concentration range. The limit of detection (LOD) and the limit of quantification (LOQ) of the p(AN-co-PTSA) film modified MTP electrodes were 37.9 µM and 126.3 µM, respectively. A standard deviation of 1.33% was observed for the first three replicates with the same modified electrode. For the time reproduced electrodes, stable reproducibility was achieved between the first electrode result and the tenth electrode result. For the modified MTP electrode, the relative standard deviation (RSD%) value was calculated to be 2.53%. As result, the molecularly imprinted electrodes prepared with p(AN-co-PTSA) film have low response time, high reproducibility, good stability, and high selectivity for the determination of MTP. [ABSTRACT FROM AUTHOR]

In the present study electrochemical detection of a-lipoic acid (α-LA) was carried out with a poly(Vanillin) modified platinum electrode p(VA)/PtE in Brinton Robinson buffer (BR) solution. The platinum electrode surface's was modified with cyclic voltammetry method. The prepared Pt electrode was characterized by cyclic voltammetry in ferrocyanide and scanning electron microscopy (SEM) images. The number of cycles and scan rate effects were studied using square wave voltammetry (SWV) in BR buffer containing 1 mM α-LA. The electrochemical oxidation of α-lipoic acid on the modified Pt electrode is influenced by the pH and it is an irreversible reaction in which one electron and one proton are transferred. Electrolyte type and pH effect were studied. The anodic peak current shows a linear increase with α-LA concentrations ranging from 0.03 mM to 2.00 mM at pH 5, the detection limit being of 0.025 mM. The α-lipoic acid quantification in synthetic urine samples was made by SWV with the modified Pt electrode. [ABSTRACT FROM AUTHOR]

In this study, we investigated the electrochemical modification of a gold electrode using poly(Lphenylalanine) and its applicability for the quantification of resveratrol (RESV). The gold electrode was modified with L-phenylalanine employing cyclic voltammetry (CV) in aqueous solution. The detection of RESV with the modified electrode was investigated by square wave voltammetry (SWV) in a phosphate buffer solution (PBS) (pH = 1.2). The analytical calibration curve for RESV showed a linear response with concentration in the oxidation peak current range from 50 to 1000 μM, with a limit of detection (LOD) of 35.16 μM and limit of quantitation (LOQ) of 105.5 μM. The application of the prepared electrochemical sensor was carried out with a standard addition method in red wine samples. [ABSTRACT FROM AUTHOR]

A novel and an easy method was developed to fabricate non-enzymatic electrochemical sensor for sensitive detection of dopamine (DA). A composite material contains graphene oxide and nickel nanoparticles was deposited on a glassy carbon electrode (GCE) surface by cyclic voltammetry. Then, gold particles were loaded on the surface of the resulting material via galvanic replacement method in order to obtain Ni-Au bimetallic nanoparticles combined with the electrodeposited graphene oxide (EG). The electrochemical behavior and the structure of the obtained electrode were characterized using scanning electron microscopy, cyclic voltammetry and impedance spectroscopy. The response of the modified electrode for DA detection is linear in the range from 2 × 10-7 to 10-4M, the sensitivity is 0.641 A M-1 and the detection limits is 10-7M. As well, it showed a high selectivity in the presence of Uric acid (UA), Ascorbic acid (AA) and glucose. Due to its low-cost, an easy process and great performance, this GCE/EG-Ni-Au(NPs) electrode can be a good candidate for the fabrication of non-enzymatic dopamine sensor. [ABSTRACT FROM AUTHOR]