Determination of dithiocarbamate pesticide residues in rice using HS-SPME-GC-QTOF

A new method was developed for the determination of dithiocarbamate pesticide residues in rice by combining headspace-solid phase microextraction with gas chromatography time-of-flight mass spectrometry (HS-SPME-GC-QTOF). Based on the derivatization principle, dithiocarbamate pesticides react with stannous chloride-hydrochloric acid solution to produce carbon disulfide (CS₂) derivatives via water-bath heating at 80 ℃ in headspace vials. Then the generated CS₂ was absorbed by SPME fiber and analyzed by GC-QTOF. The results indicated that the optimal SPME conditions were DVB/CAR/PDMS fiber, extraction temperature of 40 ℃ and extraction time of 10 min. Good linearity of CS₂ was achieved within the concentration range of 0.005~2 mg/L (R² = 0.9967). The average spiked recoveries of dithiocarbamate pesticides in rice substrates were in the range of 70%-116%, and RSDs were 1.9%-7.6%. The limit of detection (LOD) and limit of quantification (LOQ) were 0.005 mg/kg and 0.05 mg/kg, respectively. Compared with conventional detection methods, this established HS-SPME-GC-QTOF method possesses the advantages of easy automation, high precision and favorable greenness, which exhibits great application potential in routine residue analysis of rice samples.