Development of a stir-bar-sorptive extraction-liquid desorption-large-volume injection capillary gas chromatographic-mass spectrometric method for pyrethroid pesticides in water samples

Stir-bar-sorptive extraction followed by liquid desorption and large-volume injection capillary gas chromatography with mass spectrometric detection (SBSE-LD-LVI-GC-MS), had been applied for the determination of ultra-traces of eight pyrethroid pesticides (acrinathrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, fenvalerate, and permethrin cis and trans isomers) in water samples. Instrumental calibration for selected-ion monitoring acquisition and conditions that could affect the SBSE-LD efficiency are fully discussed. By performing systematic assays on 30-mL water samples spiked at the 0.10 mu g L-1 level it was established that stir-bars coated with 47 L-1 polydimethylsiloxane, an equilibrium time of 60 min (750 rpm), 5% methanol as organic modifier, and acetonitrile as back-extraction solvent, provided the best analytical performance to monitor pyrethrold pesticides in water matrices. Good accuracy (81.8-105.0%) and remarkable reproducibility (< 11.7%) were obtained, and the experimental recovery data were in good agreement with the theoretical equilibrium described by octanol-water partition coefficients (log K-O/W), with the exception of acrinathrin for which lower yields were measured. Excellent linear dynamic ranges between 25 and 400 ng L-1 (r(2) > 0.994), low quantification (3.0-7.5 ng L-1) and detection (1.0-2.5 ng L-1) limits were also achieved for the eight pyrethroid pesticides studied. The method was successfully used for analysis of tap-water and groundwater matrices spiked at the 0.10 mu g L-1, revealing the suitability of the method for determination of pyrethroid pesticides in real samples. The method was shown be reliable and sensitive and a small volume of sample was required to monitor pyrethroids at ultra-trace levels, in compliance with international regulatory directives on water quality.