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).