[Determination of bongkrekic acid in tremella and auricularia auricular by improved QuEChERS method combined with ultra-high performance liquid chromatography-triple quadrupole mass spectrometry].

An improved QuEChERS (quick, easy, cheap, effective, rugged, safe) method, combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), was used to determine bongkrekic acid (BA) in tremella and auricularia auricular. BA is a fat-soluble, fatal bacterial toxin produced by the aerobic gram-negative bacteria Burkholderia gladioli pathovar cocovenenans. Tremella and auricularia auricular, which have rich nutritional values, are traditional edible fungi in China that are very popular among Chinese consumers. However, tremella and auricularia auricular are easily contaminated by BA during storage and foaming, and this poses a great threat to food safety and human health. Therefore, establishing a rapid and efficient analysis method for detecting BA in tremella and auricularia auricular is of considerable significance. However, the BA concentration in the actual sample is very low, and the matrices of tremella fuciformis and auricularia auricular are very complex. Thus, it is necessary to employ appropriate sample pretreatment technology to extract and purify BA from tremella and auricularia auricular samples prior to instrumental analysis. In this study, the QuEChERS method, combined with UHPLC-MS/MS, was used to detect BA in tremella and auricularia auricular. The key parameters, such as extraction solvent, extraction method, and adsorbent used for cleanup, were optimized to obtain high extraction efficiency. The content of acetic acid in the extraction solution strongly influenced the extraction efficiency of BA, and acetonitrile with 5%(v/v) acetic acid was determined to be the optimum extraction solvent. After salting out, the acetonitrile extract was purified by dispersive solid phase extraction using 200 mg C18 as a cleanup adsorbent. The sample was then separated on a Waters HSS T3 column (100 mm×2.1 mm, 1.8 μm), using a water solution containing 0.01% (v/v) formic acid and 0.05% (v/v) ammonia and methanol as mobile phases. MS analysis was performed using an electrospray ionization source in the negative and multiple reaction monitoring (MRM) modes. Under the optimized conditions, the matrix effects of UHPLC-MS/MS in tremella and auricularia auricular were -6.3% and -11.5%, respectively; this indicated that the method had a significant purification effect, and the sample matrix did not affect the MS detection of BA. Further study showed that in the concentration range of 1-200 μg/L, the square of the regression coefficient of the linear equation () was greater than 0.999. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.15 μg/kg and 0.5 μg/kg, respectively. The average recoveries in samples spiked with 0.5, 10, and 50 μg/kg BA in tremella ranged from 92.4% to 102.6%, and the intra-day and inter-day relative standard deviations (RSDs) were 4.3%-4.9% and 3.2%-3.5%, respectively. For auricularia auricular, the average recoveries ranged from 89.6% to 102.3%, and the intra-day and inter-day RSDs were 2.4%-9.5% and 3.6%-4.1%, respectively. These results indicate that the proposed method has satisfactory sensitivity, accuracy, and precision. Finally, the method showed good performance when applied to the analysis of real samples. Compared with other reported methods, the LOD and LOQ of our proposed method were lower, with satisfactory recovery and precision. Taken together, this study provides an effective detection technology for the monitoring and risk control of BA in tremella and auricularia auricular.