Abstract

Tentu. Nageswara Rao¹*, A. Muralidhar Reddy², SNVS. Murthy³, Prathipati Revathi¹ and K. Suneel Kumar⁴

DOI : http://dx.doi.org/10.13005/ojc/320454

The silica nanoparticles prepared by stober’s mechanism by reaction of tetraethylorthosilicate (TEOS) with ammonia was tested for their adsorption capacity in the pre-concentration of residues of pesticides in water. The synthesized nanoparticles were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD). The size of the silica nanoparticles were 50 to 250 nm. The solid phase extraction (SPE) cartridges were prepared by filling the empty cartridges of 5.5 cm length and 0.3 cm i.d. with 200 mg of nanoparticles and protected between two polytetrafluroethylene (PTFE) frits. To avoid the passage of nanoparticles, 2% solution of polystyrene in chloroform was passed through PTFE frits and dried in air for two hours at room temperature before fitted into the cartridges. This process is to reduce the pore size of the PTFE frits. These cartridges are used in pre-concentration of different types of residues of pesticides in water. The pyrethroids tested for the pre-concentration are tetramethrin, lambda-cyhalothrin, cyphenothrin. The water samples were spiked with aliquots of pesticides and were passed through the cartridges. The amounts of the pesticides adsorbed on the cartridges were tested. The influence of temperature, sample volume, flow rate, pH and ionic strength on the performance of the cartridges was checked. The results of fortified sample analysis were compared with the data obtained from the commercially available C18 cartridges for the sample volume. The separation parameters were established for the simultaneous determination of residues using GC-EI-MS. The method was validated by means of linearity, precision, and assay accuracy. The limit of detection (LOD) and the limit of quantification (LOQ) were established based on the signal to noise ratio 3:1 and 10:1 respectively. An analytical method for the enrichment of residues using nanoparticles based SPE cartridges were developed and factors influencing the pre-concentration of residues of pyrethroids were studied and reported.

Silica nanoparticles; Pyrethroids; Solid phase extraction; GC-EI-MS

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