Determination of pyrethroid insecticides in sediment by gas chromatography--ion trap tandem mass spectrometry.

A method was developed to analyze 10 pyrethroid insecticides in sediment by gas chromatography-ion trap tandem mass spectrometry (GC-MS/MS) after accelerated solvent extraction and solid phase extraction cleanup. The MS/MS parameters included selection of the precursor and product ions, excitation mode, excitation amplitude and the stability parameter q(z), and were optimized to maximize detection sensitivity. Due to its superior ability to remove background noise, GC-MS/MS showed elevated selectivity and improved confidence in peak identification compared to GC-electron capture detector (ECD). The instrumental detection limits for GC-MS/MS ranged from 148 to 4033 fg, and the calibration curves were linear from 5 to 1000 microg/L for all of the pyrethroids except cyfluthrin. The method detection limits for pyrethroids ranged from 0.10 to 0.80 microg/kg dry sediment, while the recoveries were 59.7-128%, 60.6-90.9% and 63.2-83.6% with the relative standard deviations of 5.3-25.3%, 1.1-10.6% and 3.0-15.6% at the spiking levels of 1, 5 and 20 microg/kg, respectively. Field sediment collected from California was used to validate the newly developed method, and analytical results were comparable to those by GC-ECD in most cases. However, as the result of a cleaner background, more pyrethroids were identified by GC-MS/MS.