Department of Civil & Mineral Engineering, University of Toronto, 35 St. George Street, Toronto, Ontario M5S 1A4, Canada.
Department of Chemical Engineering & Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5, Canada.
Anal Chem. 2023 May 2;95(17):6801-6809. doi: 10.1021/acs.analchem.2c05099. Epub 2023 Apr 20.
Compound-specific isotope analysis (CSIA) is an established tool to study the fate of legacy groundwater contaminants but is only emerging for nonconventional contaminants, e.g., nitro- and amino-substituted chlorobenzenes that are widely used as industrial feedstock and the target of this work. To date, CSIA of the target compound groups used special combustion interfaces and the potential matrix interferences in environmental samples has not been assessed. We validated CSIA methods for δC, δH, and δN of four analytes from each chemical group and developed a solid-phase extraction (SPE) method to minimize matrix interferences during preconcentration of complex aqueous samples. The SPE recovery was >80% and the method quantification limits of SPE-CSIA for δC, δH, and δN were 0.03-0.57, 1.3-2.7, and 3.4-10.2 μM aqueous-phase concentrations, respectively, using 2 L of spiked MQ water. The SPE-CSIA procedure showed negligible isotope fractionation for δC (≤0.5‰), δN (≤0.5‰), and δH (≤5‰ for nitroaromatics and ≤10‰ for aminoaromatics). In addition, solvent evaporation, water sample storage up to 7 months, and SPE extract storage for 1.5 years did not change analytes' δC signatures beyond ±0.5‰. However, to avoid significant δH and δN fractionation of aminoaromatics, cartridge breakthrough should be avoided and SPE preconcentration must be conducted at pH > p + 2. Application of the method at a contaminated site showed excellent precision, at ≤0.3‰ for C and N, and ≤1.5‰ for H. The methods validated here now allow the use of multielement CSIA to track the environmental fate of nitro- and amino-substituted chlorobenzenes in complex aqueous samples.
化合物特定同位素分析（CSIA）是研究地下水污染物归宿的一种成熟工具，但仅用于非常规污染物，例如硝基和氨基取代的氯苯，这些物质被广泛用作工业原料，也是本研究的目标。迄今为止，CSIA 针对目标化合物组使用了特殊的燃烧界面，而环境样品中潜在的基质干扰尚未得到评估。我们验证了每个化学基团的四种分析物的 δC、δH 和 δN 的 CSIA 方法，并开发了固相萃取（SPE）方法，以在复杂水样的预浓缩过程中最大限度地减少基质干扰。SPE 的回收率>80%，SPE-CSIA 对 δC、δH 和 δN 的方法定量限分别为 0.03-0.57、1.3-2.7 和 3.4-10.2 μM 水相浓度，使用 2 L 加标 MQ 水。SPE-CSIA 程序对 δC（≤0.5‰）、δN（≤0.5‰）和 δH（硝基芳烃≤5‰，氨基芳烃≤10‰）的同位素分馏可忽略不计。此外，溶剂蒸发、水样储存长达 7 个月以及 SPE 提取物储存 1.5 年，不会使分析物的 δC 特征发生变化，变化幅度在±0.5‰以内。然而，为了避免氨基芳烃的显著 δH 和 δN 分馏，应避免柱穿透，并且 SPE 预浓缩必须在 pH > p + 2 下进行。该方法在污染现场的应用显示出良好的精密度，C 和 N 的精度≤0.3‰，H 的精度≤1.5‰。本文验证的方法现在可以使用多元素 CSIA 来追踪复杂水样中硝基和氨基取代氯苯的环境归宿。
