Development, validation and application of a method based on DI-SPME and GC-MS for determination of pesticides of different chemical groups in surface and groundwater samples

A simple and rapid method based on solid-phase micro extraction (SPME) technique followed by gas chromatography-mass spectrometry with selected ion monitoring (GC-MS. SIM) was developed by the simultaneous determination of 16 pesticides of seven different chemical groups 1 Six organophosphorus (trichlorfon, diazinon, methyl parathion, malathion, fenthion and ethyon), three pyrethroids (bifenhin, permethrin. cypermethrin), two imidazoles (imazalil and prochloraz), two strobilurins (azoxystrobin and pyraclostrobin), one carbamate (carbofuran), one tetrazine (clofentezine), and one triazole (difenoconazole)] in water. The pesticides extraction was done with direct immersion mode (DI-SPME) of the polyacrilate fiber (PA 85 mu m). The extraction temperature was adjusted to 50 degrees C during 30 min, while stirring at 250 rpm was applied. After extraction, the fiber was introduced in the GC injector for thermal desorption for 5 min. at 280 degrees C. The method was validated using ultra pure water samples fortified with pesticides at different concentration levels and shows good linearity in the concentrations between 0.05 and 250.00 ng mL(-1). The LOD and LOQ ranged, from 0.02 to 0.30 ng mL(-1) and 0.05 to 1.00 ng mL(-1), respectively. Intra-day and inter-day precisions were determined in two concentration levels (5.00 and 50.00 ng mL(-1)). Intra-day relative standard deviation (%R.S.D.) ranged between 3.6 and 13.6%, and inter-day (%R.S.D.) ranged between 6.3 and 18.5%. Relative recovery tests were carried out spiking the ultra pure sample with standards in three different concentration levels 0.20, 5.00 and 50.00 ng mL(-1). The recovery at 0.20 ng mL(-1) level varied from 86.4 +/- 9.4% to 108.5 +/- 10.5%, at 5.00 ng mL(-1) level varied from 77.5 +/- 10.8% to 104.6 +/- 9.6% and at 50.00 ng mL(-1) level varied from 70.2 +/- 4.6% to 98.4 +/- 8.5%. The proposed SPME method was applied in twenty-six water samples collected in the "Plato de Neopolis", State of Sergipe, Brazil. Methyl parathion was detected in five samples with an average concentration of 0.17 ng mL(-1) and bifenthrin, pyraclostrobin and azoxystrobin residues were found in three samples with average concentrations of 2.28, 3.12 and 0.15 ng mL(-1), respectively. (C) 2010 Elsevier B.V. All rights reserved.