Study on the Electrochemical Behaviors of Phenol and Three Isomers of Dihydroxybenzene at the MWCNTs Modified GCE and CV Determination of Total Phenols in Water Samples

Aliquots of 5.00 mL of standard solution of 1.00×10^-3mol·L^-1 phenol, hydroquinone, catechol and resorcinol were taken and placed separately in 4 colorimetric tubes. Portions of 3.00 mL of citric acid-sodium citrate buffer solution (pH 5.0) were added to each of the tubes and the volume of the mixture were made up to 10 mL with water. Cyclic voltammetry curves of the 4 solutions were taken at a scanning rate of 0.25 V·s^-1, using a multi-walled carbon nanotube modified glassy carbon electrode as working electrode. It was shown that linear relationship was kept between the sum of oxidation peak currents, at 0.225, 0.333, and 0.727 V, and the concentration of total phenols in the range of 0.5-2 000 μmol·L^-1, with detection limit (3S/N) of 0.15 μmol·L^-1. The method was used to determine total phenols in environmental water samples, and recovery was tested by standard addition method, giving values of recovery in the range of 95.0%-105%, and RSDs (n=6) less than 6.0%.