Solid-phase microextraction for quantitative analysis of organophosphorus pesticides in environmental water samples

Solid-phase microextraction (SPME) is a relatively new technique that appears as a convenient and efficient extraction method in contrast with more complex techniques used for pesticide residue analysis based on liquid-liquid and solid-phase extraction. This extraction procedure involves the absorption of analytes into a polymeric film coated onto a fine silica fiber directly dipped in the aqueous sample. An SPME procedure for the determination of 12 organophosphorus pesticides in clean environmental water samples at low ng/ml concentration level has been developed by optimising variables involved in extraction and desorption. The absorption equilibrium has been estimated by mathematical treatment of the process using an expression that describes experimental absorption time profiles. The method was evaluated according to the reproducibility, linearity range and limits of detection using two different fiber coatings: 100 microm polydimethylsiloxane and 85 microm polyacrylate. The limits of detection obtained using nitrogen-phosphorus detection ranged between 0.01 and 0.2 ng/ml with relative standard deviations lower than 15% at the 1 ng/ml level. The method showed good linearity between 0.1 and 10 ng/ml with regression coefficients ranging between 0.97 and 0.999. Determination of organophosphorus pesticides in water samples in concentration below 0.1 ng/ml can be easily carried out with this fast, economic and solvent-free SPME procedure.