Preparation and characterisation of sol-gel hybrid sorbent methyltrimethoxysilane-chloropropyltriethoxysilane for solid-phase extraction of selected organophosphorus pesticides

A new sol-gel hybrid methyltrimethoxysilane-chloropropyltriethoxysilane (MTMOS-CPTES) was prepared and used as solid-phase extraction (SPE) sorbent. The extraction efficiency of the prepared sol-gel hybrid MTMOS-CPTES was assessed by using three selected organophosphorus pesticides (OPPs) namely chlorpyrifos, profenofos and malathion as model analytes. Gas chromatography-mass spectrometry (GC-MS) was used for detection of OPPs. Several SPE vital parameters such as sample loading volume, types of eluting solvent and volume of eluting solvent were optimised to identify the best extraction conditions. The SPE-MTMOS-CPTES method showed good linearity in the range of 0.05-1 μg mL-1 while SPE-C18 method linearity ranged from 0.25-2 μg mL-1 with coefficient of determination, r2 > 0.995. The SPE-MTMOS-CPTES method showed good limits of detection (LODs) (0.01-0.07 μg mL-1) and limits of quantification (LOQs) (0.03-0.21 μg mL-1) compared to SPE-C18 method LODs (0.13-0.16 μg mL-1) and LOQs (0.38-0.49 μg mL-1). The LODs obtained for SPE-MTMOS-CPTES were 2.3-6.5× lower than the LODs of commercial C18. The developed SPE-MTMOS-CPTES method showed good repeatability (RSD 2.4-4.7%, n=3) compared to C18 (RSD 3.5-5.4%, n=3). The SPE-MTMOS-CPTES method and SPE-C18 method were applied to red apple and purple grape samples. The developed SPE-MTMOS-CPTES method provided satisfactory recovery (88.33-120.7%) with good relative standard deviations (RSD) ranging from 1.6% to 3.3% (n=3) in comparison to commercial SPE-C18 sorbent (70.3-100.2%, RSDs 6.3-8.8%, n=3).