Determination of 9 Phenoxy Acid Herbicides in Soil by Solid Phase Extraction and LC/MS/MS

A method for the determination of 9 phenoxy acid herbicides in soil by solid phase extraction and LC/MS/MS with matrix correction was developed. The sample was treated by ultrasonic extraction twice with 1.5% formic acid in acetonitrile. The extract was cleaned up with NH sub(2) solid phase extraction column. A C sub(18) column with formic acid in pure water/methanol mixture as the mobile phase was used under gradient elution. Mass spectral acquisition was done in negative ion mode by multiple reactions monitoring ( MRM ). Two transitions per compound were used to provide qualitative and quantitative analysis. There were good linear relationships in the range of 2-250 mu g/L for 9 phenoxy acid herbicides. The correlation coefficients were in the range of 0. 9927-0. 9972. The method detection limits were in the range of 1. 66-3. 82 mu pg/kg. The average recoveries at three spiked levels (10, 40, 200 pg/kg) ranged from 85. 3% to 110. 0% with the relative standard deviations (RSD) of 3. 2% -12%.