Abstract:

A method was established for the determination of 5 herbicide residues (metolachlor, clomazone, acetochlor, metalaxyl and pyrazosulfuron) in cereals using gas chromatography-mass spectrometry (GC-MS). Samples were extracted with acetonitrile and cleaned up with primary secondary amine (PSA) and amino group packing materials. The analysis was carried out using GC-MS with electron impact (EI) source in a simultaneous full scan-selected ion monitoring mode. Quantification was performed using the internal standard method. This method exhibited good linearity within the range from 0.05 to 0.5 mg/L with a correlation coefficient of 0.999. Average recoveries for metolachlor in 6 cereal species spiked at 0.05, 0.1 mg/kg and 0.2 mg/kg ranged from 85% to 99%, with a RSD of smaller than 5%. For this method, matrix solid phase dispersion extraction used gives a rapid sample preparation approach. This method is free of interference from matrices and highly sensitive, and is exactly suitable for the daily large-scale determination of metolachlor, clomazone, acetochlor, metalaxyl and pyrazosulfuron residues in cereals.

Key words: primary secondary amine (PSA), gas chromatography-mass spectrometry (GC-MS), herbicide, cereals