Abstract:

To investigate the contamination of dithiocarbamate pesticides in the samples and their transfer during the processing, through optimizing pretreatment conditions and chromatographic conditions, this study established a gas chromatography-flame photometry (GC-FPD) method to determine thiram and mancozeb residual quantity in Jiawei Xiaoyao tablets. Dithiocarbamate pesticides reacted to form CS₂ in hydrochloric acid medium containing stannous chloride. The precision of headspace injection method was not good, and the presence of high concentration of HCl in headspace gas would cause corrosion of gas chromatography injection components. Therefore, in this study, headspace injection was changed to solution injection, and isooctane was used to extract the detection indexes. The linear range of this method was 0.02-2.0 μg/mL, and the R of correlation coefficient was greater than 0.99. The average recoveries of mancozeb and thiram were 99%-115% at the level of 5, 20, 100 μg/kg, and the RSD of them was less than 2.0%, both met the detection requirements of trace pesticide residues. A total of 36 batches of Jiawei Xiaoyao tablets, and its Chinese herbal medicines and extracts were detected. The results showed that the residues of CS₂ in the samples met the relevant residue limits of European Pharmacopoeia and Chinese Food Safety Standards. In this study, a GC method for the determination of mancozeb and thiram in Jiawei Xiaoyao tablets was established, which is sensitive, accurate and reliable, and could be used for the monitoring of pesticide residues in Jiawei Xiaoyao tablets and its intermediates.

Key words: mancozeb, thiram, Jiawei Xiaoyao tablets, gas chromatography, transfer of pesticides