Fast Analysis of Chlorinated Phenoxy Herbicides in Environmental Samples by Negative ESI LC-MS/MS – 14337

This paper describes the analysis procedure and results for environmental herbicide samples by a negative ESI LC-MS/MS method. After the preparation of aqueous and soil samples, the extracts are directly injected into a high performance liquid chromatography system coupled to negative eletrospray ionization (ESI-) tandem mass spectrometry. The sample preparation incorporates modified hydrolysis steps from EPA 8151 to ensure herbicides containing a variety of functional groups are captured in the reported concentration. Herbicides in the final extract have been converted to their carboxylic acid form for LC-MS/MS analysis. The liquid chromatograph uses a narrow-bore C-18 column and acidic acetonitrile mobile phase. The triple quadruple mass spectrometer uses a Multiple Reaction Monitoring (MRM) mode for each herbicide compound enabling highly selective identification. The method was certified for herbicide targets from EPA 8151. Parallel blind performance evaluation tests run concurrently between EPA 8151 and TestAmerica’s EPA 8321 LC-MS/MS herbicide method indicate that the LC-MS/MS method has superior performance on accuracy, precision, sensitivity, and selectivity in addition to the aforementioned advantages of sample preparation efficiency and TAT for both aqueous and solid samples. The increased reliability of the qualitative identification of the herbicides using the LCMS/MS method produces more reliable and defensible data.