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Mycotoxins are potential food pollutants produced by fungi. Among them, aflatoxins (AFs) are the most toxic. Therefore, AFs were selected as models, and a sensitive, simple and green graphene oxide (GO)-based stir bar sorptive extraction (SBSE) method was developed for extraction and determination of AFs with high performance liquid chromatography-laser-induced fluorescence detector (HPLC-LIF). This method improved the sensitivity of AFs detection and solved the deposition difficulty of the direct use of GO as adsorbent. Several parameters including a spiked amount of NaCl, stirring rate, extraction time and desorption time were investigated. Under optimal conditions, the quantitative method had low limits of detection of 2.4-8.0 pg/mL, which were better than some reported AFs analytical methods. The developed method has been applied to soy milk samples with good recoveries ranging from 80.5 to 102.3%. The prepared GO-based SBSE can be used as a sensitive screening technique for detecting AFs in soy milk.

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A sensitive and reliable method using a two-phase hollow fiber liquid-phase microextraction (HF-LPME) pretreatment technique was developed for simultaneously screening multiple b-blockers in environmental samples. In this study, heptanol was chosen as the optimal extraction solvent, and six bblockers with a wide range of polarities were extracted across the porous walls of hollow fibers and into the acceptor phase (AP). The fundamental parameters affecting the extraction efficiency (EE) of analytes including extraction time, temperature, pH of the donor phase (DP) and AP, stirring speed, volume of the sample solution, ionic strength and the type of hollow fiber membrane were studied and optimized.Under optimal conditions, extracts were analyzed by HPLC with ultraviolet detection (UV). Finally, satisfactory results were obtained, good linearity was observed for all b-blockers in the range of 0.16-200 ng mL À1 , limits of detection (LODs) were between 0.08 and 0.5 ng mL À1 , the intra-and inter-day precision values of the six b-blockers were 1.0-2.2% and 1.4-2.7%, respectively. The recovery with RSDs was less than 2.2% for the pretreatment method. The proposed technique was successfully applied for screening multiple b-blockers in complex aqueous samples with the best specificity and provided a simple and reliable new means for the self-checking of laboratories at the basic level.