title: Development of a stir-bar-sorptive extraction-liquid desorption-large-volume injection capillary gas chromatographic-mass spectrometric method for pyrethroid pesticides in water samples.
abstract: 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 microg L(-1) level it was established that stir-bars coated with 47 microL 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 pyrethroid 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) (r2>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 microg 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.
authors.affiliation: Chemistry and Biochemistry Department, University of Lisbon, Campo Grande Ed. C8, 1749-016 Lisbon, Portugal.
authors.forename: P
authors.initials: P
authors.lastname: Serôdio
authors.forename: J M F
authors.initials: JM
authors.lastname: Nogueira
mesh_terms: D000327:Adsorption; D020650:Combinatorial Chemistry Techniques; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D015394:Molecular Structure; D011722:Pyrethrins / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013499:Surface Properties; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D011722:Pyrethrins; D014874:Water Pollutants, Chemical