Determination of organochlorine pesticides in river water by gas chromatography-negative-ion chemical-ionization mass spectrometry using large volumeinjection

A method for the determination of 24 organochlorine pesticides by gas chrom atography-mass spectrometry (GC-MS) with negative-ion chemical-ionization ( NICI) using programmable temperature vaporizer (PTV)-based large volume inj ection (LVI) is described. The ion source temperature was determined to be 150 degreesC for the optimized NICI-selected ion monitoring (SIM) condition s. PTV inlet parameters were also optimized. The sensitivities of the pesti cides by splitless-GC-NICI-MS were approximately 7.8-360 times higher than those of the pesticides by splitless-GC-EI-MS. The sensitivities of the pes ticides by LVI-GC-NICI-MS were over 80 times higher than those of the pesti cides by spiltless-GC-NICI-MS. This method was applied to the determination of the pesticides in river water using micro liquid-liquid extraction as s ample preparation. The recoveries of the pesticides from a river water samp le spiked with standards at 2 ng l(-1) and 20 ng l(-1) were 75-111% (RSD, 2 .9-15%) and 92-105% (RSD, 0.5-5.6%), respectively. The methodical detection limits ranged from 0.004 to 2.2 ng l(-1).