U.S. Department of Agriculture, Wyndmoor, PA19038, USA.
J Agric Food Chem. 2011 Jul 27;59(14):7544-56. doi: 10.1021/jf104606j. Epub 2011 Apr 13.
Quantitative method validation is a well-established process to demonstrate trueness and precision of the results with a given method. However, an assessment of qualitative results is also an important need to estimate selectivity and devise criteria for chemical identification when using the method, particularly for mass spectrometric analysis. For multianalyte analysis, automatic instrument software is commonly used to make initial qualitative identifications of the target analytes by comparison of their mass spectra against a database library. Especially at low residue levels in complex matrices, manual checking of results is typically needed to correct the peak assignments and integration errors, which is very time-consuming. Low-pressure gas chromatography-mass spectrometry (LP-GC-MS) has been demonstrated to increase the speed of analysis for GC-amenable residues in various foods and provide more advantages over the traditional GC-MS approach. LP-GC-MS on a time-of-flight (ToF) instrument was used, which provided high sample throughput with <10 min analysis time. The method had already been validated to be acceptable quantitatively for nearly 150 pesticides, and in this study of qualitative performance, 90 samples in total of strawberry, tomato, potato, orange, and lettuce extracts from the QuEChERS sample preparation approach were analyzed. The extracts were randomly spiked with different pesticides at different levels, both unknown to the analyst, in the different matrices. Automated software evaluation was compared with human assessments in terms of false-positive and -negative results. Among the 13590 possible permutations with 696 blind additions made, the automated software approach yielded 1.2% false presumptive positives with 23% false negatives, whereas the analyst achieved 0.8% false presumptive positives and 17% false negatives for the same analytical data files. False negatives frequently occurred due to challenges at the lowest concentrations, but 70% of them involved certain pesticides that degraded (e.g., captafol, folpet) or otherwise could not be detected. The false-negative rate was reduced to 5-10% if the problematic analytes were excluded. Despite its somewhat better performance in this study, the analyst approach was extremely time-consuming and would not be practical in high sample throughput applications for so many analytes in complicated matrices.
定量方法验证是一种经过充分验证的过程，可用于证明给定方法的结果的准确性和精密度。然而，当使用该方法时，对定性结果的评估也是一个重要的需求，用于估计选择性并为化学鉴定制定标准，特别是对于质谱分析。对于多分析物分析，通常使用自动仪器软件通过将其质谱与数据库库进行比较来对目标分析物进行初步定性鉴定。特别是在复杂基质中残留水平较低的情况下，通常需要手动检查结果以更正峰分配和积分错误，这非常耗时。已经证明，低压气相色谱-质谱（LP-GC-MS）可以提高各种食品中 GC 相容残留物的分析速度，并提供比传统 GC-MS 方法更多的优势。使用飞行时间（ToF）仪器进行 LP-GC-MS 分析，该方法提供了高样品通量，分析时间<10 分钟。该方法已经在定量方面得到验证，可接受近 150 种农药，在这项定性性能研究中，总共分析了来自 QuEChERS 样品制备方法的草莓、番茄、土豆、橙子和生菜提取物的 90 个样品。在不同基质中，以分析师未知的不同水平，对提取物进行了不同农药的随机添加。比较了自动软件评估与人类评估在假阳性和假阴性结果方面的差异。在进行了 696 次盲加的 13590 种可能的排列中，自动软件方法的假阳性率为 1.2%，假阴性率为 23%，而分析师对相同的分析数据文件的假阳性率为 0.8%，假阴性率为 17%。假阴性经常发生在最低浓度的情况下，但其中 70%涉及到某些降解的农药（例如，克菌丹、灭菌丹）或其他无法检测到的农药。如果排除有问题的分析物，假阴性率可降低至 5-10%。尽管在这项研究中该方法的性能略好，但分析师方法非常耗时，并且在如此多的复杂基质中的分析物高样品通量应用中不实用。
