DETERMINATION OF SULFONIC-ACID DEGRADATES OF CHLOROACETANILIDE AND CHLOROACETAMIDE HERBICIDES IN GROUNDWATER BY LC MS/MS/

An analytical method is presented which permits qualitative and quanti tative analysis of sulfonic acid degradates of three chloroacetanilide herbicides (acetochlor, alachlor, and metolachlor) and one chloroacet amide herbicide (dimethenamid) in groundwater at trace levels with det ermination by LC/MS/MS. The analytes were isolated from groundwater by solid-phase extraction (SPE). The final samples were analyzed by reve rsed-phase HPLC: with MS/MS detection utilizing a pneumatically assist ed, and heat-assisted electrospray interface (TurboIonSpray). Unique p recursor/product ion pairs were obtained in the MS/MS mode which permi tted conclusive identification of each analyte, even when the analytes coeluted. Quantification was performed by generation of an external c alibration curve. Excellent linearity was obtained over a calibration range from 0.25 to 10 ng injected on-column, with all linear correlati on coefficients exceeding 0.999. Method performance for this analytica l procedure was validated by analyzing groundwater samples fortified a t levels of 0.1, 1, and 50 ppb. The average recovery at each fortifica tion level for each analyte exceeded 89%, Excellent method precision w as demonstrated with percent relative standard deviations of less than 10% for all analytes at all fortification levels.