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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 a simple, highly sensitive, and selective electrochemical method was developed for determination of the low concentration curcumin (CUR) using a poly(vanillinco- caffeic acid) p(Van-CA) modified platinum electrode. Electrode modification was carried out electrochemically with cyclic voltammetry (CV) method. For this purpose; a solution of 6 mM vanillin (Van) and 6 mM caffeic acid (CA) in phosphate buffer solution (PB) adjusted to pH 7.4 was used. Then, electrochemical behaviour of CUR on the platinum electrode modified with p(Van-CA) was investigated by using CV and differential pulse voltammetry (DPV) methods. Tween 20 as surfactant was used to increase the solubility and stability of CUR in this study. CUR responses of the modified electrode showed that it was selective, sensitive and stable. A linear calibration graph was acquired in the high concentration range of 0.1 to 1.0 mM CUR. Correlation coefficient (R²) was calculated as 0.9951 from this linear calibration curve. The correlation coefficient for the low concentration range 0.01 to 0.07 mM was also calculated from 0.9950. LOD (limit of detection) and LOQ (limit of quantitation) of the developed method were determined as 0.005 mM and 0.015 mM, respectively. However, the detection of CUR in spices samples was made with this method. The recovery efficiency of the p(Van-CA) modified Pt electrode (p(Van-CA)/PtE) was calculated range of 96% and 102% for three different spices samples. Finally; developed method has been shown that it has fast, low cost, simple, reproducible, high accuracy and precision (99.6%) for sensitive and selective determination of CUR by using p(Van-CA)/PtE as effective novel electrode. [ABSTRACT FROM AUTHOR]

In this study, an electrochemical sensor was developed for the electrochemical determination of melanin. For this purpose, phosphate buffer salt (PBS, pH 7.00) solution was used as an electrolyte, 2,5-dimethylfuran (2,5-DMF) as a monomer, Pt wire as the auxilary electrode, Ag/AgCl electrode as the reference electrode and a platinum electrode as the working electrode. The modification of the electrode was performed by polymerization of 2,5-DMF at the bare Pt electrode surface using the cyclic voltammetry method. Parameters such as film thickness, scan rate and pulse amplitude with prepared 2,5-DMF modified platinum electrode (p(2,5-DMF)/PtE) were optimized by square wave voltammetry (SWV) in PBS buffer containing melanin. In optimum conditions, the anodic peak height showed a linear increase with the melanin concentration. The limit of detection (LOD) and limit of quantitation (LOQ) were calculated to be 0.088 mmol/l and 0.292 mmol/l, respectively, with melanin concentrations ranging from 0.10 to 2.20 mmol/l and the correlation coefficient (R2) was calculated as 0.9985. Stability of the prepared sensor was found to be 99.63% by using the reproducibility experiments (n = 15). [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]