[Study and comparison of detection methods for prochloraz and its metabolite residue in garlic bolting]

Two analytical methods for the determination of prochloraz and its metabolite residues in garlic bolting were established and compared. In the QuEChERS method, the sample was extracted with acetonitrile and purified in a QuEChERS purification tube, and then, the contents of prochloraz and its metabolite 2,4,6-trichlorophenol were determined by gas chromatography. The hydrolysis method involved extraction of the sample with acetonitrile, hydrolysis by pyridine hydrochloride, purification with sulfuric acid, and determination of the prochloraz content by gas chromatography. The standard curve in the hydrolysis and QuEChERS methods showed a good linear relationship in the concentration range of 0.01-2 mg/L, and the correlation coefficient (r²) was greater than 0.999. The limit of quantitation (LOQ) for prochloraz in the hydrolysis method was 0.005 mg/kg. The LOQ for prochloraz in the QuEChERS method was 0.039 mg/kg, and that for 2,4,6-trichlorophenol was 0.003 mg/kg. At three spiked levels in the sample, the recoveries were 81.5%-105.4%, and the relative standard deviations (RSDs) were between 1.3%-6.8%. In the determination of positive samples, the hydrolysis method can detect the total amount of prochloraz and its main metabolites. QuEChERS method can detect the presence and contents of prochloraz and its main metabolite 2,4,6-trichlorophenol. These two methods can complement each other for the detection and confirmation of prochloraz and its metabolites in garlic bolting.