New sol-gel silica-based hybrid materials and their applications in the analysis of organophosphorus pesticides in various matrices

Abstract

Commercial sorbent materials are based on polymeric materials and are normally designed to extract polar or non-polar analytes separately and are expensive. In the current work, these problems were addressed through the development of three new in-house sol-gel hybrid organic-inorganic materials which have become important materials for the analysis of organic pollutants residues. Two of these new sol-gel hybrid organic-inorganic materials were synthesized, characterized and used as sorbents for two sample preparations techniques namely, stir bar sorptive extraction (SBSE) and solid phase extraction (SPE). Their extraction performances were evaluated for extraction of selected organophosphorus pesticides (OPPs) in water, fruit and vegetable samples. The first material, 3-(2-aminoethylamino) propyltrimethoxysilane-polydimethylsiloxane, was synthesized as SBSE sorbent and combined with high performance liquid chromatography with ultraviolet detector. Both polar and non-polar OPPs were extracted simultaneously using the new sorbent and it showed high selectivity for the OPPs as compared to commercial polydimethylsiloxane (PDMS) Twister™ SBSE sorbent. The second new sol-gel hybrid material synthesized, methyltrimethoxysilane-cyanopropyl-triethoxysilane, was used as SPE sorbent for OPPs extractions prior to gas chromatography-mass spectrometry analysis. This new sol-gel hybrid sorbent showed lower detection limits (10-70 pg mL-1) and excellent recoveries (94.93-99.98%) against commercial C18 SPE sorbent (0.05-1.23 ng mL-1). Parameters affecting sol-gel process were optimized for each sorbent material to obtain the most efficient sorbent materials and to improve the extraction of the more polar compounds. The third new cyano-based sol-gel hybrid film was synthesized using molecular imprinting (MIP) with methamidophos for sensing OPPs applications in the analysis of vegetable and fruit samples. Low-cost large-scale production, ease of synthesis, and the predictability of specificity by logical design, provide economic advantages which have encouraged researchers to further develop the methodology and applications of MIPs. Cyano-based sol-gel hybrid film act as functional monomers providing more recognition sites through hydrogen bonds with methamidophos for template recognition. The electrochemical behaviour of methamidophos at the sol-gel sensor was characterized by cyclic voltammetry. The results showed that the new method is able to provide a sensitive, anti-interferent and rapid detection of methamidophos in real samples.