PDF(Pubmed)
Abstract：
Analysis of low-level organic contaminants in complex matrices is essential for monitoring global food safety. However, balancing sample throughput with complex experimental designs and/or sample clean-up to best reduce matrix effects is a constant challenge. Multiple strategies exist to mitigate these effects, with internal standard-based methods such as isotope dilution mass spectrometry (IDMS) being the most advantageous. Here, multiple internal calibration strategies were investigated for the quantification of ochratoxin A (OTA) in wheat samples by liquid chromatography-mass spectrometry (LC-MS). Internal standard-based quantitation methods such as single (ID1MS), double (ID2MS), and quintuple (ID5MS) isotope dilution mass spectrometry, as well as external standard calibration, were explored and compared. A certified reference material (CRM) of OTA in flour, MYCO-1, was used to evaluate the accuracy of each method. External calibration generated results 18-38% lower than the certified value for MYCO-1, largely due to matrix suppression effects. Concurrently, consistently lower OTA mass fractions were obtained for the wheat samples upon quantitation by external calibration as opposed to ID1MS, ID2MS, and ID5MS. All isotope dilution methods produced results that fell within the expected range for MYCO-1 (3.17-4.93 µg/kg), validating their accuracy. However, an average 6% decrease in the OTA mass fraction was observed from results obtained by ID1MS compared to those by ID2MS and ID5MS. Upon scrutiny, these differences were attributed to an isotopic enrichment bias in the isotopically labelled internal standard [13C6]-OTA that was used for ID1MS, the OTAL-1 CRM. The advantages and limitations of each isotopic method are illustrated.
摘要：
分析复杂基质中的低水平有机污染物对于监测全球食品安全至关重要。然而,平衡样品通量与复杂的实验设计和/或样品清理以最好地减少基体效应是一个持续的挑战。存在多种策略来减轻这些影响，基于内标的方法，如同位素稀释质谱（IDMS）是最有利的。这里,通过液相色谱-质谱（LC-MS）研究了多种内部校准策略，以定量小麦样品中的曲霉毒素A（OTA）。基于内标的定量方法，如单一(ID1MS)，double(ID2MS),和五重（ID5MS）同位素稀释质谱，以及外部标准校准，进行了探索和比较。面粉中OTA的认证参考材料（CRM），MYCO-1用于评估每种方法的准确性。外部校准产生的结果比MYCO-1的认证值低18-38％，这主要是由于基质抑制作用。同时,与ID1MS相比，通过外部校准定量时，小麦样品获得的OTA质量分数始终较低，ID2MS,ID5MS所有同位素稀释方法产生的结果均在MYCO-1的预期范围内（3.17-4.93µg/kg），验证其准确性。然而,与ID2MS和ID5MS相比,从ID1MS获得的结果观察到OTA质量分数平均降低6%。经过审查，这些差异归因于同位素标记的内标[13C6]-OTA用于ID1MS的同位素富集偏差，OTAL-1CRM。说明了每种同位素方法的优点和局限性。
