Determination of tebufenpyrad and oxadiazon by solid-phase microextraction and gas chromatography-mass spectrometry

A method for determination of trace amounts of the pesticides tebufenpyrad and oxadiazon, previous solid-phase microextraction (SPME), was developed using gas chromatography-mass spectrometry and selected ion monitoring (GC-MS; SIM). Both pesticides were extracted with a fused silica fiber coated with 100 mum polydimethylsiloxane. The effects of pH, ionic strength, sample volume, extraction and desorption times as well as extraction temperature were studied. The linear concentration range of application was 0.5 - 250 ng mL(-1) for both compounds, with a detection limit of 0.06 ng mL(-1) for tebufenpyrad and 0.02 ng mL(-1) for oxadiazon. SPME-GC-MS analysis yielded good reproducibility (RSD between 7.5 - 10.1%). It was used to check the eventual existence of tebufenpyrad and oxadiazon above this limit in water and soil samples from Granada (Spain) as well as in human urine samples. The method validation was completed with spiked matrix samples. It can be applied as a monitoring tool for water, soil and urine in the investigation of environmental and occupational exposure to tebufenpyrad and oxadiazon.