A new sensitive voltammetric determination of thymol based on MnY nanozeolite modified carbon paste electrode using response surface methodology

Abstract

In this paper, a simple voltammetric method has been reported for the thymol determination using MnY nanozeolite modified carbon paste electrode (MnY/CPE). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and N2 adsorption-desorption isotherm were used to characterize the structure of synthesized NaY and MnY nanozeolites. Also, cyclic voltammetry (CV), chronoamperometry, amperometry and differential pulse voltammetry (DPV) were used to investigate the performance of the modified electrode. The oxidation peak current of thymol was increased dramatically at the MnY/CPE surface against bare CPE and their overpotentials decreased. The effects of pH, modifier amount (MnY%), scan rate and step potential were investigated on the electrochemical response of thymol electro-oxidation based on response surface methodology. Results from this method indicated that pH of 7.0, 20% of MnY nanozeolite in the modified CPE, scan rate (0.06 V s−1) and step potential (7 mV) results in the maximum current density. Under the optimized conditions, linear response was obtained over the range of 0.5–28 μM and also, detection limits was found to be 0.243 μM by DPV method in the MnY/CPE surface. The diffusion coefficient and catalytic rate constant for the electrooxidation of thymol were calculated to be 1.5 × 10−6 cm2 s−1 and 2.6 × 105 cm3 mol−1 s−1, respectively. The fabricated electrode (MnY/CPE) showed good stability, reproducibility and repeatability as well as high recovery. The practical application of the MnY/CPE was demonstrated by measuring the concentration of thymol in thymex syrup as real samples. The proposed method is simple, rapid and inexpensive and can be utilized as a valuable analytical tool in quality control of the pharmaceutical industry.