A graphene-coated magnetic nanocomposite for the enrichment of fourteen pesticides in tomato and rape samples prior to their determination by gas chromatography-mass spectrometry

A graphene-based magnetic nanocomposite (Fe3O4@SiO2–G) was synthesized and used as the adsorbent for the extraction of fourteen pesticides in tomato and rape samples prior to their gas chromatography-mass spectrometry (GC-MS) detection. Various experimental parameters affecting the extraction efficiencies, such as the amount of Fe3O4@SiO2–G, extraction time, the pH and salt concentration of the sample solution and desorption conditions were investigated. Under optimized experimental conditions, good linearity existed in the range of 1.0–100.0 ng g−1 for all the analytes with the correlation coefficients (r) ranging from 0.9972 to 0.9996. The limits of detection (S/N = 3) of the method for the compounds were between 0.005 and 0.030 ng g−1 for the vegetable samples. Good reproducibilities were obtained with the relative standard deviations (RSDs) below 12.5% (n = 5). The recoveries of the method were in the range between 83.2% and 110.3%.