POLY(DIMETHYLSILOXANE)-POLY(VINYL ALCOHOL) COATED SOLID PHASE MICROEXTRACTION FIBER FOR CHLORPYRIFOS ANALYSIS

Abstract

Traditional liquid – liquid extraction of pesticides consumes large volumes of organic solvent which are hazardous to the operator and is not environment friendly. Solid phase microextraction (SPME) is a solvent less extraction method which is safer to the operator and is environmental friendly. A sol-gel hybrid fibre coating material, poly(dimethylsiloxane)-poly(vinyl alcohol) (PDMS-PVA) was synthesized and used in head space solid phase microextraction (HS-SPME) of chlorpyrifos. The thickness of the synthesised PDMS-PVA fiber coating was 13.5 μm and it is thermally stable up to 400 °C. The PDMS-PVA sol-gel hybrid fiber was also stable to two organic solvents tested, acetonitrile and dichloromethane (1 hour dipping) and showed no significant changes in extraction performance for chlorpyrifos. Extracted chlorpyrifos was analysed using gas chromatography electron capture detector (GC-ECD). Optimum SPME parameters affecting the PDMS-PVA HS-SPME performance namely extraction time (15 min), extraction temperature (50 °C), desorption time (5 min), desorption temperature (260 °C) and stirring rate (120 rpm) were used for extraction. It was found that HSSPME using PDMS-PVA sol-gel fiber gave significantly better extraction performance of chlorpyrifos compared to commercial 100 μm PDMS fiber. The PDMS-PVA fiber showed excellent operational performances such as temperature stability (up to 380 °C), coating lifetime (up to 170 times use) and organic solvent stability. The PDMS-PVA-HS-SPME method showed excellent recovery for chlorpyrifos from tomatoes (98.0 , 5.9 RSD) at 0.01 μg/g spiked level (5 times lower than maximum residue limit set by European Union).