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

FONTANA, A.; WUILLOUD, R.; CAMARGO, A.; ALTAMIRANO, J.

Santa Fe

Workshop; 2nd Latin American Pesticide Residue Workshop. Food and Environment; 2009

Universidad Nacional del Litoral, Facultad de Ingeniería Química- Laboratorio Central

Organophosphates pesticides (OPs) are widely used for agricultural practices because they help to control pests and diseases. The extensive distribution of this group of pesticides caused several problems to apiculture industry including residues in hive products. Honey is an exported product of Argentina and it is subjected to several quality controls. For the determination of pesticides in honey samples, routine methods typically involve several sample preparations steps such as extraction, clean-up and pre-concentration before instrumental analysis. The goal of this work was to development and validation of a method for OPs determination in honey of different regions of Argentine using coacervative-microextraction ultrasound-assisted back-extraction-gas chromatography-mass spectrometry (CM-UABE-GC-MS). A mass of 0.5 g honey samples contained into 10 mL aqueous solution pH 2 was extracted with 100 µL 100 g L-1 Triton X-114 at 80 °C. Under these conditions the coacervate-phase started get agglomerated and decanted from the aqueous bulk. After centrifugation at 3500 rpm for 5 min the analytes were ultrasound-assisted back-extracted from the coacervate phase into hexane. Again, two phases were formed: the coacervate-phase (at the button of the tube) and the hexane one. A 1 µL of the hexane phase was injected and analyzed into the GC-MS. The GC column used was VF-5ms (25m×0.25 mm, 0.25µm film thickness). Under optimum conditions, extraction efficiency (EE) ranged from 7 to 47%. The LODs of the analytes were ranged from 0.3 ng g-1 to 2.1 ng g-1 with RSDs values lower than 10.7%. The linear range was 5-1000 ng g-1 for Fenitrothion, Parathion and Methidathion; and 1.5-1000 ng g-1 for Chlorpirifos with r² higher than 0.9992. The developed CM-UABE-GC-MS method was applied to the analysis of pesticides in real honey samples; none of them reported the presence of the studied pesticides. The CM-UABE can be successfully applied for extraction and pre-concentration of polar pesticides. Even though, EE was low, the obtained LODs are suitable for real world applications. An important aspect of the proposed methodology to point out is the low organic solvent consumption. All these results disclosed that CM-UABE-GC-MS is a sensitive, reproducible, rapid and versatile technique.