Coacervative microextraction: innovative preconcentration technique for determination of organophosphates pesticides in honey samples by GC-MS

ARIEL R. FONTANA; RODOLFO G. WUILLOUD; ALEJANDRA B. CAMARGO; JORGELINA C. ALTAMIRANO

Santa Fe, Argentina

Workshop; 2do WORKSHOP LATINOAMERICANO SOBRE RESIDUOS DE PESTICIDAS. ALIMENTOS Y MEDIOAMBIENTE; 2009

Polybrominated diphenyl ethers (PBDEs) are flame retardants used in a variety of consumer products including plastics, foams, textiles and electronic equipment. PBDEs are persistent environmental contaminants that bioaccumulate into the highest levels of the food chain [1]. The analysis of PBDEs in water samples is of particular interest; however their low concentrations demands the use of pre-concentration techniques prior their determination. Therefore, it is necessary to count on highly efficient and reliable pre-concentration techniques for their determination by GC. A DLLME technique for extraction and pre-concentration of PBDEs in waters prior gas chromatography-mass spectrometry (GC–MS/MS) was developed and validate.A 5 mL of water sample were extracted by adding 1 mL of acetone (disperser solvent) containing 20 µL of CCl4 (extraction solvent) and mixed up. The cloudy solution formed was kept in a thermostatic bath at 35 °C for 5 min and then centrifuged at 3500 rpm for 2 min. After centrifugation, 1 µL aliquot of the CCl4 phase was injected into GC–MS for analysis. GC–MS/MS analyses were performed on a gas chromatograph equipped with an ion trap mass detector. The GC column used was VF-5ms (25m×0.25 mm, 0.25µm film thickness).Under optimum conditions, extraction efficiency >99% was achieved. The enrichment factors (EF) were ≥583. The LODs of the analytes were ranged from 0.2 to 0.4 ng L-1 with RSDs values between 9.4 to 12.9%. A satisfactory linearity was observed in the range of 2-1000 ng L-1 with r² ≥0.9991. The analytical methodology was validated in real water samples at two different concentration levels (10 and 50 ng L-1) and analyzed by DLLME-GC–MS/MS. This study led to satisfactory robustness with recoveries ≥ 95 %. The PBDEs contents in the analyzed samples were below the detection limit of the proposed methodology.Under optimized working conditions, high EF were obtained for the target analytes allowing to reach detection limits in the order of picogram per liter with an acceptable precision. The method was successfully applied to determine PBDEs in real water samples, showing good recoveries and no matrix effect. Additionally, it is important to point out that DLLME is a low organic solvent consuming extraction technique, which turns it into a low cost and environmentally friendly technique.