School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.
School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, NSW, 2052, Australia.
Anal Chim Acta. 2019 Jun 13;1058:127-135. doi: 10.1016/j.aca.2019.01.038. Epub 2019 Jan 31.
The analysis of persistent organic pollutants, such as perfluoroalkyl substances (PFAS) including perfluorooctanoic acid (CFCOOH, PFOA) and perfluorooctane sulfonate (CFSO, PFOS) by hyphenated chromatography-mass spectrometry methods is crucial in ensuring water quality. One of the challenges in PFOA and PFOS analysis is the separation of linear and branched isomers that have the same mass-to-charge ratio but can have different toxicological properties. Current methods that are used for separating isomeric PFAS require relatively long analysis times (min to h) that can limit throughput. An emerging technique for the direct analysis of isomeric compounds is differential mobility spectrometry (DMS), which can rapidly separate gas phase ions prior to detection by mass spectrometry (MS). However, an ion mobility-based method for the analysis of PFAS has not been reported in the literature. Herein, high-resolution DMS-MS is used to separate and detect isomeric PFAS compounds for the first time in a separation process that occurs in milliseconds. The resolution of isomeric peaks increased by over 200% and 500% for PFOA and PFOS isomers, respectively, using a DMS carrier gas composed of 50:50% He:N by volume compared to 100% N, which was crucial in the separation of PFAS isomers under these conditions. Linear, secondary-branched, and tertiary-branched isomers of PFOA and PFOS including those that differ by the position of a single perfluoromethyl group can be resolved by DMS-MS. The DMS compensation field required to transmit different isomers increases as the extent of branching increases. For isomeric PFASs with a single branching point, the compensation field for optimal transmission also increases as the perfluoromethyl group is positioned closer to the carboxylate and sulfonate groups under these conditions. These results indicate that high-resolution DMS-MS should be a useful approach for the rapid analysis of isomeric PFAS.
通过联用色谱-质谱法分析持久性有机污染物，如全氟烷基物质（PFAS），包括全氟辛酸（CFCOOH，PFOA）和全氟辛烷磺酸（CFSO3，PFOS），这对水质监测至关重要。在 PFOA 和 PFOS 分析中，面临的挑战之一是分离具有相同质荷比但可能具有不同毒理学性质的直链和支链异构体。目前用于分离 PFAS 异构体的方法需要相对较长的分析时间（分钟至小时），这可能会限制通量。一种新兴的用于直接分析异构体化合物的技术是差分迁移谱（DMS），它可以在通过质谱（MS）检测之前快速分离气相离子。然而，在文献中尚未报道用于分析 PFAS 的基于离子迁移的方法。在此，首次在毫秒级的分离过程中使用高分辨 DMS-MS 来分离和检测 PFAS 异构体。与使用 100% N 相比，使用体积比为 50:50% 的 He:N 作为 DMS 载气时，PFOA 和 PFOS 异构体的峰分辨率分别提高了 200%和 500%以上，这对于在这些条件下分离 PFAS 异构体至关重要。可以通过 DMS-MS 来分辨 PFOA 和 PFOS 的直链、二级支链和三级支链异构体，包括那些仅通过单个全氟甲基位置不同的异构体。在这些条件下，随着支化程度的增加，传输不同异构体所需的 DMS 补偿场增大。对于具有单个支化点的异构体 PFAS，在最佳传输时，补偿场也随着全氟甲基位置更靠近羧酸根和磺酸根基团而增大。这些结果表明，高分辨 DMS-MS 应该是快速分析异构体 PFAS 的有用方法。
