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Simultaneous determination of traces of pyrethroids, organochlorines and other main plant protection agents in agricultural soils by headspace solid-phase microextraction-gas chromatography.

Journal of chromatography. A (2008-03-19)
Maria Fernandez-Alvarez, Maria Llompart, J Pablo Lamas, Marta Lores, Carmen Garcia-Jares, Rafael Cela, Thierry Dagnac
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.

MATERIALS
Product Number
Brand
Product Description

Supelco
SPME fiber assembly polyacrylate (PA), df 85 μm (PA), for use with manual holder, needle size 24 ga
Supelco
SPME fiber assembly polyacrylate (PA), df 85 μm (PA), for use with autosampler, needle size 24 ga
Supelco
SPME fiber assembly polyacrylate (PA), df 85 μm (PA), for use with autosampler, needle size 23 ga