title: Simultaneous determination of traces of pyrethroids, organochlorines and other main plant protection agents in agricultural soils by headspace solid-phase microextraction-gas chromatography.
abstract: A solvent-free and simple method based on headspace solid-phase microextraction (HS-SPME) was developed in order to determine simultaneously 36 common pesticides and breakdown products (mostly pyrethroids and organochlorine compounds) in soil. The analysis was carried out by gas chromatography with micro-electron-capture detection (GC-microECD). As far as we know, this is the first study about the SPME of pyrethroid insecticides from soil. Factors such as extraction temperature, matrix modification by addition of water, salt addition (% NaCl) and fiber coating were considered in the optimization of the HS-SPME. To this end, a 3 x 2(3-1) fractional factorial design was performed. The results showed that temperature and fiber coating were the most significant variables affecting extraction efficiency. A suitable sensitivity for all investigated compounds was achieved at 100 degrees C by extracting soil samples wetted with 0.5 mL of ultrapure water (0% NaCl) employing a polyacrylate (PA) coating fiber. Using the recommended extraction conditions with GC-microECD, a linear calibration could be achieved over a range of two orders of magnitude for both groups of analytes. Limits of detection (LODS) at the sub-ng g(-1) level were attained and relative standard deviations (RSDs) were found to be lower than 14% for both groups of pesticides. Matrix effects were investigated by the analysis of different soil samples fortified with the target compounds. The method accuracy was assessed and good recovery values (>70%, in most cases) were obtained. The method was also validated with a certified reference material (RTC-CRM818-050), which was quantified using a standard addition protocol. Finally, the proposed HS-SPME-GC-microECD methodology was further applied to the screening of environmental soil samples for the presence of the target pesticides.
authors.affiliation: Departamento de Quimica Analitica, Nutricion y Bromatologia, Instituto de Investigacion y Analisis Alimentario, Campus Sur, Universidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Fernandez-Alvarez
authors.forename: Maria
authors.initials: M
authors.lastname: Llompart
authors.forename: J Pablo
authors.initials: JP
authors.lastname: Lamas
authors.forename: Marta
authors.initials: M
authors.lastname: Lores
authors.forename: Carmen
authors.initials: C
authors.lastname: Garcia-Jares
authors.forename: Rafael
authors.initials: R
authors.lastname: Cela
authors.forename: Thierry
authors.initials: T
authors.lastname: Dagnac
mesh_terms: D000383:Agriculture; D002849:Chromatography, Gas; D006843:Hydrocarbons, Chlorinated / Q000032:analysis*; D010575:Pesticides / Q000032:analysis* / Q000302:isolation & purification; D011722:Pyrethrins / Q000032:analysis*; D012015:Reference Standards; D015203:Reproducibility of Results; D012987:Soil / Q000032:analysis*; D052617:Solid Phase Microextraction / Q000379:methods*; D012997:Solvents; D013696:Temperature
chemical_list: D006843:Hydrocarbons, Chlorinated; D010575:Pesticides; D011722:Pyrethrins; D012987:Soil; D012997:Solvents