Micropollutants are frequently detected in groundwater. Thus, the question arises whether they are eliminated by natural attenuation so that pesticide degradation would be observed with increasing residence time in groundwater. Conventional analytical approaches rely on parent compound/metabolite ratios. These are difficult to interpret if metabolites are sorbed or further transformed. Compound-specific stable isotope analysis (CSIA) presents an alternative for identifying degradation based on the analysis of natural isotope abundances in pesticides and their changes during degradation. However, CSIA by gas chromatography-isotope ratio mass spectrometry is challenged by the low concentrations (ng/L) of micropollutants in groundwater. Consequently, large amounts of water need to be sampled requiring enrichment and clean-up steps from interfering matrix effects that must not introduce artefacts in measured isotope values. The aim of this study was to evaluate the accuracy of isotope ratio measurements of the frequently detected micropollutants atrazine, desethylatrazine and 2,6-dichlorobenzamide after enrichment from large water volumes (up to 100 L) by solid-phase extraction with consecutive clean-up by HPLC. Associated artefacts of isotope discrimination were found to depend on numerous factors including organic matter content and extraction volume. This emphasizes the necessity to perform a careful method evaluation of sample preparation and sample pre-treatment prior reliable CSIA.

中文翻译：

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大体积提取过程中微污染物的同位素分馏：地下水中低 ng/L 浓度的莠去津、去乙基莠去津和 2,6-二氯苯甲酰胺的关键方法评估

地下水中经常检测到微污染物。因此，出现的问题是它们是否通过自然衰减消除，以便随着在地下水中停留时间的增加而观察到农药降解。传统的分析方法依赖于母体化合物/代谢物的比率。如果代谢物被吸附或进一步转化，这些很难解释。化合物特定的稳定同位素分析 (CSIA) 提供了一种基于农药中天然同位素丰度及其降解过程中变化的分析来识别降解的替代方法。然而，气相色谱-同位素比质谱法的 CSIA 受到地下水中微污染物的低浓度 (ng/L) 的挑战。最后，需要对大量水进行采样，需要进行富集和净化步骤，以免干扰基质效应，这些效应不得在测得的同位素值中引入人为因素。本研究的目的是评估经常检测到的微污染物莠去津、去乙基莠去津和 2,6-二氯苯甲酰胺通过固相萃取和连续净化从大量水（高达 100 L）中富集后同位素比测量的准确性通过 HPLC。发现同位素鉴别的相关人工制品取决于许多因素，包括有机物含量和提取量。这强调了在可靠的 CSIA 之前对样品制备和样品预处理进行仔细方法评估的必要性。本研究的目的是评估经常检测到的微污染物莠去津、去乙基莠去津和 2,6-二氯苯甲酰胺通过固相萃取和连续净化从大量水（高达 100 L）中富集后同位素比测量的准确性通过 HPLC。发现同位素鉴别的相关人工制品取决于许多因素，包括有机物含量和提取量。这强调了在可靠的 CSIA 之前对样品制备和样品预处理进行仔细方法评估的必要性。本研究的目的是评估经常检测到的微污染物莠去津、去乙基莠去津和 2,6-二氯苯甲酰胺通过固相萃取和连续净化从大量水（高达 100 L）中富集后同位素比测量的准确性通过 HPLC。发现同位素鉴别的相关人工制品取决于许多因素，包括有机物含量和提取量。这强调了在可靠的 CSIA 之前对样品制备和样品预处理进行仔细方法评估的必要性。发现同位素鉴别的相关人工制品取决于许多因素，包括有机物含量和提取量。这强调了在可靠的 CSIA 之前对样品制备和样品预处理进行仔细方法评估的必要性。发现同位素鉴别的相关人工制品取决于许多因素，包括有机物含量和提取量。这强调了在可靠的 CSIA 之前对样品制备和样品预处理进行仔细方法评估的必要性。