Determination of Dithiocarbamate and Its Breakdown Product Ethylenethiourea in Fruits and Vegetables

Abstract

Abstract Improved methods for determination in fruits and vegetables of ethylene bisdithiocarbamate (EBDC) residues as carbon disulfide by gas–liquid chromatographic headspace analysis and of othylenethio-urea (ETU) residues by liquid chromatography (LC) are described. Improvements to the EBDC procedure include increased sensitivity by use of 140 mL crimp seal samples bottles fitted with silicone seals, which are leak-proof and reduce headspace volume; use of a Porapak column, which allows use of higher column temperature for better residue separation; and inclusion of thiopheno as an internal standard for bettor quality control. The relationship between the logarithm of the response of carbon disulfide divided by the thiophene response versus concentration of carbon disulfide is expressed by the regression equation Y = 1.011 X + 0.008, with a correlation coefficient r2 = 0.993. Mean recoveries from 8 commodities spiked with mancozcb at 1 and 3 mg/kg, equivalent to 0.473 and 1.419 mg/kg carbon disulfide, are 94.2 ±10 and 98.3 ± 13%, respectively. The Improved LC procedure for ETU residue analysis requires minimal cleanup of sample extract, no derivatization prior to injection, and no specialized LC detectors for quantitation. The UV detector response at 240 nm Is linearly related to ETU concentration [Y = (3.18X – 0.778) × 1000. r2 = 0.997]. Moan ETU recovery from 5 commodities spiked at 0.2 to 5 mg/kg is 93.9 ± 6%. ETU residues of 0.02 to 0.25 μg/g were detected in macerated samples of fruits and vegetables spiked with man-cozeb at 5 μg/g and incubated at room temperature for 3 days. The improved procedures were used to analyze EBDC and ETU residues in fruits and vegetables sampled at a wholesale Sydney produce market. Approximately 30% of samples tested contained EBDC residues, whereas ETU residues in the same samples were below the detection limit of the analytical method (<0.02 mg/kg).