Rapid Determination of Bisphenol A in Water and Soil by Electrochemical Method Based on Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotubes and Poly Cetyl Trimethyl Ammonium Bromide

Based on high conductivity and high sensitivity of multi-walled carbon nanotubes (MWCNTs) and poly cetyl trimethyl ammonium bromide (p-CTAB), the glassy carbon electrode (GCE) modified with MWCNTs and p-CTAB was prepared and used as working electrode (MWCNTs/p-CTAB/GCE) for the rapid determination of bisphenol A (BPA) in water and soil. GCE modified with p-CTAB (p-CTAB/GCE) was obtained by scanning 0.5 g·L^-1 CTAB solution for 20 cycles by cyclic voltammetry (CV) with GCE as working electrode. 5 μL of 1.96 g·L^-1 MWCNTs standard solution was dropped on the surface of p-CTAB/GCE, and MWCNTs/p-CTAB/GCE was obtained after drying. Water sample was filtered, and 2 mL of an aliquot was mixed with 8 mL of 0.3 mol·L^-1 phosphate buffer (pH 7.0) for test. After drying, grinding and screening, 25 g of soil sample was extracted with 50 mL of ethanol for twice, concentrated to about 1 mL, and made its volume up to 10 mL with ethanol. 2 mL of an aliquot was mixed with 8 mL of 0.3 mol·L^-1 phosphate buffer (pH 7.0) for test. Using MWCNTs/p-CTAB/GCE as the working electrode, titanium rod as the counter electrode and saturated calomel electrode as the reference electrode, BPA in the test solution was enriched at 0.2 V for 150 s with stirring rate of 800 r·min^-1, and determined by differential pulse voltammetry (DPV). The surface of MWCNTs/p-CTAB/GCE showed porous voids and porous network structures by scanning electron microscope characterization. The electrochemical behavior of BPA on MWCNTs/p-CTAB/GCE was investigated by DPV, CV and electrochemical impedance spectroscopy. The results showed that the electrochemical oxidation of BPA on MWCNTs/p-CTAB/GCE was irreversible and controlled by adsorption, and linear relationship between concentration of BPA and its oxidation peak current was kept in the range of 0.08-20 μmol·L^-1, with detection limit of 0.02 μmol·L^-1. The BPA standard solution was determined by the same MWCNTs/p-CTAB GCE for 10 times, with RSDs of the determined values of 5.0%. Test for recovery was made on the actual samples by standard addition method, giving results in the range of 82.0%-106%, and RSDs (n=5) of the determined values were in the range of 1.6%-8.1%.