Simultaneous Determination of Aflatoxin B1, Bisphenol A, and 4-Nonylphenol in Peanut Oils by Liquid-Liquid Extraction Combined with Solid-Phase Extraction and Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

An analytical method based on liquid-liquid extraction combined with solid-phase extraction and isotope dilution-ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was well developed for simultaneous determination of aflatoxin B1 (AFB1), bisphenol A (BPA), and 4-nonylphenol (4-NP) in peanut oil. After adding isotope internal standards, the samples were firstly diluted by normal hexane and then extracted by acetonitrile and Carb/PSA solid-phase extraction cartridge in sequence to obtain the extracted solution. All the extracted solution was merged and was subsequently dried to near dryness by a mild nitrogen stream. Three target analytes were separated on a Phenomenex Luna C18 chromatographic column, quantified by an internal standard method and detected by ESI positive (ESI+) and negative (ESI-) subsection acquisition modes under multi-reaction monitoring (MRM) conditions. Results demonstrated that the three target analytes exhibited excellent linearity in their corresponding concentration ranges of 0.1-100.0 mu g/L with correlation coefficients all greater than 0.998. The corresponding method limits of quantitation (MLOQ, S/N = 10) of AFB1, BPA, and 4-NP were 0.2, 1.0, and 2.0 mu g/kg, respectively. Moreover, the mean recoveries for negative samples spiked at three concentration levels were calculated between 87.7 and 105.1% with relative standard deviation (RSD, n = 6) ranging from 2.2 to 7.9% and the interday precision (n = 5) ranging from 5.0 to 8.7%. Finally, the method was successfully applied to analyze 52 peanut oil samples, and AFB1 and 4-NP were detected in 43 samples with the concentrations in the ranges of 0.5-69.4 and 9.3-77.8 mu g/kg, respectively. None of BPA was detected in any samples.