Magnetic silica aerogels with high efficiency for selective adsorption of pyrethroid insecticides in juices and tea beverages
An effective and reliable method, magnetic solid phase extraction based on magnetic silica aerogels, has been developed and used for the enrichment of 3 pyrethroid insecticides (including fenpropathrin, lambda-cyhalothrin and cypermethrin) from juices and tea beverages. The magnetic silica aerogels were successfully synthesized by an acid–base two-step catalytic sol–gel method using tetraethylorthosilicate (TEOS) as a precursor solution, and characterized. Several influencing factors that could affect magnetic solid-phase extraction (MSPE) performance including adsorbent dosage, adsorption time, the pH of the solution, ionic strength, elution solvent type, the volume of elution solvent and the elution time were systematically investigated and optimized. Under the optimal conditions, an excellent linearity was shown for fenpropathrin and lambda-cyhalothrin in the 0.04–4 ng mL−1 range and cypermethrin in the 0.08–8 ng mL−1 range, and the correlation coefficients were in the range of 0.9985–0.9996. The recoveries of fenpropathrin, lambda-cyhalothrin and cypermethrin ranged from 79.5% to 102.7% with relative standard deviation (RSD) less than 9.7%. The detection limit of the method was from 0.008 to 0.024 ng mL−1. The MSPE method, based on magnetic silica aerogels, possessed high sensitivity, efficiency, and convenience, and was suitable to determine the trace pyrethroid insecticides in juices and tea beverages.