Determination of zinc-thiazole residues in water, soil and Cucumis sativus L. by high performance liquid chromatography

A new residue determination method for zinc-thiazole in water, soil and Cucumis sativus L. samples has been developed and validated by high performance liquid chromatography with diode array detection. Zinc-thiazole (bis-(2-amino-5-mercapto-1,3,4-thiadiazole)zinc) was converted into AMT (2-amino-5-mercapto-1,3,4-thiadiazole) in the alkaline solution. The quantitative analysis of zinc-thiazole was then achieved by the determination of AMT. Samples were reacted with sodium sulfide, and extracted with acetonitrile at 40℃. The mixture was filtered and the pH of the filtrate was adjusted to 3. The filtrate clean-up was conducted by liquid-liquid extraction (LLE) using ethyl acetate. The determination was carried out using HPLC-DAD (313 nm) with BDS Hypersil C18 column and V (acetonitrile):V (0.1% acetic acid)=10:90 were used as the mobile phase. The analyte was quantified by external standard method. The results showed that the linear range of this method was 0.1-10 mg/L for AMT, 0.2-5 mg/L for zinc-thiazole. And the correlation coefficients were above 0.999 5. The limits of detection (LODs) for AMT was 0.05 mg/L. The average recovery of zinc-thiazole in water, soil and C. sativus at three spiked levels (0.05-5 mg/kg) were 81%-110% with relative standard deviations (RSDs, n=5) ranged from 0.7% to 6.4%. The limit of quantification (LOQs) of zinc-thiazole in water, C. sativus and soil samples were 0.03, 0.05 and 0.05 mg/kg, respectively. This method is simple, accurate and reliable, which is suitable for the determination of zinc-thiazole in water, soil and C. sativus.