Silica anionite for solid phase extraction: synthesis and optimisation

Abstract

Solid-phase extraction is used in laboratories in order to concentrate and purify samples for the further use for analysis. For that, a particulate stationary phase or monolith with corresponding functional groups is used together with a mobile phase which contains desired analyte. For this work silica gel was used modified with 3-glycidyloxypropyltrimethoxysilane (GLYMO) and diethylamine (DEA) in order to attach amino groups for positive charge of stationary phase. The modification was carried out using a different ratio of GLYMO and DEA, different temperatures, different solvent as reaction medium and different modification time for the optimisation of the adsorptive properties of the monolith. The amount of nitrogen fixed on the monolith was determined using Kjeldahl method for nitrogen determination. Results have shown that the highest amount of nitrogen (0.617%) is obtained at the ratio of GLYMO and DEA of 1:1.2 in alkaline solution using dimethyl sulfoxide as a solvent and proceeding the modification for 24 hours in ca. 85ºC temperature, meanwhile the lowest amount (0.08%) of nitrogen is obtained at the ratio of GLYMO and DEA of 1:1.2 in alkaline solution using dimethyl sulfoxide as a solvent, proceeding the modification for 7.5 hours at ca. 68ºC temperature. The optimized monolith will be used in further experiments for solid-phase extraction of phytochemicals.