Per- and polyfluoroalkyl substances (PFAS) have become ubiquitous environmental contaminants found in many parts of the globe and in all environmental compartments. The phase out of legacy C8 PFAS has led to an increase in functionality of the carbon backbone chain to include ether linkages and branching points. With the increased production of functionalized PFAS, there remains a paucity of information regarding the occurrence of constitutional isomers in the environment. In this study, a series of novel PFAS constitutional isomers were detected by high resolution mass spectrometry and characterized by MS/MS in river water collected weekly over 40 weeks. Constitutional isomers of C₄H₂F₈O₄S₁ (-1.8 ± 2.5 ppm) were detected for the first time in 83% of the samples analyzed and the MS/MS fragmentation patterns clearly indicated there were two coeluting isomers present. Two chromatographically resolved peaks with deprotonated molecular formula C₇H₁F₁₄O₅S₁ (1.9 ± 2.7 and 2.2 ± 3.1 ppm) were detected in 85% of the samples measured. MS/MS fragmentation patterns and a standard provided by a fluorochemical manufacturer confirmed the two isomers. A series of novel chlorinated PFAS were detected (M-1: C₁₁H₁Cl₁F₂₀O₅ 0.9 ± 2.7 ppm and C₁₄H₁Cl₁F₂₆O₆ 2.1 ± 2.6 ppm) in 34% of the water samples analyzed. The exact structure is not confirmed. River sediment collected below the water sample location contained several of the compounds detected in the water column illustrating the connectivity between the environmental compartments. Results highlight the need for further studies on the occurrence of isomers and authentic standards to confirm structures.

全氟烷基物质和多氟烷基物质（PFAS）已成为在全球许多地区和所有环境隔间中普遍存在的环境污染物。逐步淘汰传统的C8 PFAS导致碳主链的功能性增加，包括醚键和分支点。随着功能化PFAS产量的增加，关于环境中结构异构体的出现的信息仍然很少。在这项研究中，通过高分辨率质谱检测了一系列新颖的PFAS组成异构体，并通过40周每周收集的河水中的MS / MS进行了表征。C ₄ H ₂ F ₈ O ₄ S _1的结构异构体在83％的分析样品中首次检测到（-1.8±2.5 ppm），MS / MS碎片图谱清楚表明存在两种共洗脱异构体。在85％的样品中检测到两个具有去质子化的分子式C ₇ H ₁ F ₁₄ O ₅ S _1的色谱分离峰（1.9±2.7和2.2±3.1 ppm）。MS / MS碎片图谱和含氟化合物制造商提供的标准品证实了这两种异构体。检测到一系列新型的氯化PFAS（M-1：C ₁₁ H ₁ Cl ₁ F ₂₀ O ₅ 0.9±2.7 ppm和C ₁₄ H ₁在所分析的34％的水样品中含有Cl ₁ F ₂₆ O ₆ 2.1±2.6 ppm）。尚未确认确切的结构。在水样位置下方收集的河流沉积物包含在水柱中检测到的几种化合物，说明了环境隔室之间的连通性。结果强调需要进一步研究异构体的发生和确定结构的真实标准品。