Determination of Carbendazim and Thiabendazole Residues in Vegetables from Fresh Markets in Muang District, Phetchabun Province Using High-Performance Liquid Chromatography

Abstract

Carbendazim and thiabendazole are substances of the benzimidazole group commonly used as fungicides in vegetables and fruits before or after harvest. However, long-term exposure to these substances is harmful to human and animal health. This research aimed to determine carbendazim and thiabendazole content in vegetable samples using high-performance liquid chromatography. The samples were extracted using a QuEChERS extraction and cleaned up with dispersive solid phase extraction. The chromatographic separation was performed on the C18 column with isocratic elution using water-methanol (50:50 %v/v) as mobile phase at a flow rate of 1.0 mL/min and the column temperature was 40°C. The injection volume was 5 µL. The fluorescence detector was set at 285 nm as an excitation wavelength and 340 nm as an emission wavelength. From the method validation using carbendazim and thiabendazole standards, the analytical method had selectivity. The linear calibration curves were obtained at the concentration range of 0.050-3.00 mg/kg with good correlation coefficients of determination more than 0.995. The limits of quantitation of carbendazim and thiabendazole were at 0.065 and 0.074 mg/kg, respectively. The accuracy and precision of the analytical method were acceptable. Fifty samples of vegetables from fresh markets in Muang district, Phetchabun province were taken for analysis of carbendazim and thiabeldazole content according to the validated method. It was found that thiabeldazole was not detected in all samples. However, carbendazim was detected in onion samples but not exceeding the Maximum Residue Limit (MRL) set by the Ministry of Public Health. It was also detected in lettuce and kale in the amounts exceeding the MRL values that would be harmful to consumers.