Synthesis and applications of new cyanopropyl-triethoxy silane and cyanopropyltriethoxysilane nanomaterials as sorbents of selected organophosphorus analysis

Abstract

Conventional extraction methods such as liquid-liquid extraction for organophosphorus pesticides (OPPs) are tedious, time consuming, environmental unfriendly, hazardous to the operator, and use large volumes of organic solvents. These problems are addressed by the synthesis and development of two extraction methods based on two new in-house sol-gel nanosorbents for use in solid phasebased extraction. The two new nanomaterials, namely cyanopropyltriethoxysilane (CNPrTEOS) and silica nanoparticles functionalized with CNPrTEOS (SiO2-NPs- CNPrTEOS) were prepared via a sol-gel process. Synthesized sorbents were characterized by using Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric and nitrogen adsorption analysis. The particle sizes of both nanomaterials were between 20 to 500 nm with high surface areas of 379 m2 g-1 and 570 m2 g-1 for CNPrTEOS and SiO2-NPs- CNPrTEOS, respectively. The effects of several sol-gel synthesis parameters were evaluated to optimize sorbent extraction efficiency and increase the extraction of polar and non-polar OPPs simultaneously. The selected OPPs were analysed using high performance liquid chromatography with ultraviolet detector. The synthesized CNPrTEOS was successfully applied as a solid phase extraction (SPE) sorbent to extract three selected OPPs, namely dicrotophos, diazinon and chlorpyrifos. The synthesised SiO2-NPs-CNPrTEOS material was used as new sorbent in SPE and dispersive micro solid phase extraction (D-µ-SPE). Several effective extraction parameters in SPE and D-µ-SPE were optimized. The proposed SPE method based on CNPrTEOS and SiO2-NPs-CNPrTEOS exhibited good linearity between 0.3-100 µg L-1, high enrichment factor (833-1666) and low (0.088-0.214 µg L-1) limits of detection (LODs = 3 × SD/m). Finally, the proposed D-µ-SPE method based on the SiO2-NPs-CNPrTEOS successfully determined the selected polar and non polar OPPs in water samples with excellent recoveries (101.21-109.12%). LODs at ultratrace level (0.047-0.059 µg L-1) were obtained with 10 min of extraction time, small amount of sorbent (50 mg) and low organic solvent volume (150 µL). The LODs obtained using the proposed SPE and D-µ-SPE methods were well below the maximum residue limit (MRL) set by the European Union and LODs of commercial CN-SPE cartridges. The developed environmentally friendly methods using SPECNPrTEOS, SPE-SiO2-NPs-CNPrTEOS and D-µ-SPE-SiO2-NPs-CNPrTEOS provided precise, accurate and excellent recoveries of OPPs from water samples. These new sol-gel materials showed high potential for use as sorbent in solid phasebased extraction of pesticides of variety polarity.