Major Degradation Pathway of Thiuram in Tap Water Processed by Oxidation with Sodium Hypochlorite

Abstract

Thiuram (3 microM), a fungicide, was incubated in deionized water by adding 0-100 mg/L free chlorine at 30 degrees C for 30 min, and the solution was analyzed by HPLC and IC. The byproducts were identified by LC/MS, EI-MS, infrared, and (13)C NMR spectra and a reduction technique using 2-mercaptoethanol. On the basis of these results, it was found that the oxidation of thiuram with sodium hypochlorite initially produced an intermediate dimethylthiocarbamoyl dimethylcarbamoyl disulfide, which was finally degraded to bis(dimethylcarbamoyl) disulfide, its trisulfide, and dimethylamine. Subsequently, it was suggested that monitoring of bis(dimethylcarbamoyl) disulfide, its trisulfide, and dimethylamine should be included for the management and control of thiuram in tap water processed by oxidation with sodium hypochlorite.

Determination of dithiocarbamates and metabolites in plants by liquid chromatography–mass spectrometry

“…The method is unsatisfactory in a certain number of pesticide/crop combination as fruits with high acid content (orange and lemon), for which thiram and disulfiram were not recovered, and nuts for which disulfiram was not recovered. The hypothesis of thiram and disulfiram decomposition by the action of organic acids, juice of fruits and vegetables, or enzymatic reactions has been widely mentioned in the literature [8,15,[21][22][23][24][25]. Heise et al [8] postulated that procedures admitting small sample amounts and hence requiring an intense homogenization are not appropriated to determine these compounds because the contact between the residues on the peel of the fruit and vegetables and the flesh tissue should be avoided.…”

“…Liquid chromatography (LC) and capillary electrophoresis (CE) with UV and/or electrochemical detection are the techniques most frequently used to discriminate and determine the different DTCs subclasses [13][14][15][16][17][18][19][20][21][22][23][24]. Determination of ETU and PTU in food commodities is achieved by LC with selective detectors or derivatization with a halogen or S-benzyl-N-(pentafluorobenzyl)-2-imidazolinethione and subsequent analysis by GC [3,11,[25][26][27][28].…”

“…A still more difficult step is the sample preparation because the instability of DTCs, which are affected especially by pH, temperature and plant components [8,10,22,28]. The common techniques for the extraction and clean up of DTCs from matrices isolate these compounds by liquid extraction or solid-phase extraction (SPE) using, or not, some forms of ion-pairs [14,16,19,[21][22][23][24].…”

“…The common techniques for the extraction and clean up of DTCs from matrices isolate these compounds by liquid extraction or solid-phase extraction (SPE) using, or not, some forms of ion-pairs [14,16,19,[21][22][23][24]. ETU and PTU are polar and water soluble, and their extraction from fruits and vegetables is critical [3,11,27].…”

Identification of degradation products of thiram in water, soil and plants using LC-MS technique

“…Other uses of this pesticide are as seed protector, animal repellent, accelerator and vulcanization agent in the rubber industry. [1] It is considered to have low short-term toxicity. Thiram is slightly toxic by ingestion and inhalation and moderately toxic by dermal absorption.…”