Validation and analysis of thiram, a dithiocarbamate, as CS₂ from soybean (Glycine max) samples on GC–MS

Abstract

A method was validated for the estimation of dithiocarbamates in soybean leaf, pod, seed, oil and in soil. Method involves acid hydrolysis and reduction of dithiocarbamates to carbon disulfide in the presence of stannous chloride and hydrochloric acid. Thiram was spiked in the samples at the levels of 0.5, 2.5 and 5.0 µg g⁻¹ and estimated as carbon disulfide on gas chromatograph coupled to single quadrupole (GC–MS) by monitoring m/z 76 (quantitation ion). Retention time of carbon disulfide was 2.119. All method validation parameters like linearity, accuracy and precision were within the acceptable range as per SANTE (in European Union Guidance document on analytical quality control and method validation procedures for pesticide residues analysis in food and feed. Document No. SANTE/11945/2015, 2015). The linearity, expressed as correlation coefficient, was 0.997. Accuracy was expressed as percent recovery. The recovery ranged from 87 to 102% in soybean leaf, 81–98% in soybean pod, 83–113% in soybean seed, 85–109% in soybean oil and 75–109% in soil at different fortification levels. Precision, expressed as relative standard deviation, ranged from 0.1 to 0.11 in various soybean samples. Limit of quantitation (LOQ) was 0.32 µg g⁻¹ for soybean leaf, 0.18 µg g⁻¹ for pod, 0.19 µg g⁻¹ for seed and 0.1 µg g⁻¹ for oil and soil. To our knowledge, this is the first report describing the extraction and analysis of thiram, a dithiocarbamate (DTCs) from soybean (oilseeds and oil). The method described here can be extended for the estimation of DTCs in other oilseeds and oils.