Determination of capsaicinoids by magnetic solid phase extraction coupled with UPLC-MS/MS for screening of gutter oil

Capsaicinoids, including capsaicin, dihydrocapsaicin and N-vanillylnonanamide have been identified as characteristic markers for gutter oil. In this study, the nanocomposite of graphene oxide-Fe₃O₄ (GO-Fe₃O₄) was synthesized by a co-precipitation method, and applied to magnetic solid phase extraction (MSPE) process. The capsaicin, dihydrocapsaicin and N-vanillylnonanamide extracted in gutter oil were analyzed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Under the optimized pretreatment conditions, the limit of detection (LOD) and limit of quantification (LOQ) are 0.15 and 0.4 µg L^-1, respectively. The linear range is 0.4-200 µg L^-1, and the correlation coefficients (R²) are over 0.996 for all three compounds. The recoveries range from 81.2% to 103.3% for soybean oil and 71.2% to 84.3% for rapeseed oil. The values of matrix effect range in 87.6%-105.5% and 83.4%-110.6% and the intra-day RSDs range from 2.8%-4.6% to 4.8%-6.1% for soybean oil and rapeseed oil, respectively. The adsorbent can be reused for multiple times with no appreciable loss of adsorption capability. The present methodology has high potential for screening of gutter oil in food samples, thus having importance for food safety monitoring.