Compound specific isotope analysis (CSIA) of phthalates and non-targeted isotope analysis (NTIA) of SPE-extractable organic carbon in dilute aquatic environments

Isotope ratio analysis of total organic carbon (TOC) is well-established for the study of rivers, lakes, and oceans. Similarly, these aquatic systems are routinely surveyed to quantify natural and anthropogenic organic compounds and pollutants, including such things as pharmaceuticals, illicit drugs, and phthalates. We merged these two approaches to demonstrate compound specific isotope analysis (CSIA) on four phthalate esters and non-targeted isotope analysis (NTIA) on a gas chromatography isotope ratio mass spectrometry (GC-IRMS) platform. Water from the Rivers Foss and Trent and a waste-water treatment plant (WWTP) effluent was sampled, followed by solid phase extraction (SPE) and GC-IRMS. Di–ethyl hexyl phthalate (DEHP) concentration in the effluent was 0.20 µg/L while it was 0.22 µg/L and 0.14 µg/L in the Trent and Foss Rivers, respectively. CSIA δ 13C values for selected phthalates measured in river and effluent samples ranged from −24.3‰ to −28.8‰. NTIA returned over 100 compounds which in aggregate aligned well with published values for isotope analysis of TOC. NTIA demonstrated that the volatile SPE-extractable fraction of TOC has high heterogeneity with δ 13C from −26.8‰ to −44.3‰ for matched compounds in both rivers. GC-IRMS can be applied to dilute environmental systems using both compound specific and non-targeted strategies