Supercritical Fluid Chromatography Coupled to High-Resolution Mass Spectrometry Reveals Persistent Mobile Organic Compounds with Unknown Toxicity in Wastewater Effluents

Abstract

Broad screening approaches for monitoring wastewater are normally based on reversed-phase liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS). This method is not sufficient for the very polar micropollutants, neglected in the past due to a lack of suitable analytical methods. In this study, we used supercritical fluid chromatography (SFC) to detect very polar and yet-undetected micropollutants in wastewater effluents. We tentatively identified 85 compounds, whereas 18 have only rarely been detected and 11 have not previously been detected in wastewater effluents such as 17α-hydroxypregnenolone, a likely transformation product (TP) of steroids, and 1H-indole-3-carboxamide, a likely TP from new synthetic cannabinoids. Suspect screening of 25 effluent wastewater samples from 8 wastewater treatment plants revealed several distinct potential pollution sources such as a pharmaceutical company and a golf court. The analysis of the same samples with LC−HRMS showed clearly how SFC increases the ionization efficiency for low-molecular-weight micropollutants (m/z < 300 Da) by a factor 2 to 87 times, which significantly improved the mass spectra for identifying very polar compounds. In order to assess which micropollutants might be of environmental concern, literature and toxicological databases were screened. There was a lack of available hazard and bio-activity data for regulatory-relevant in vitro and in vivo assays for >50% of the micropollutants. Especially, 70% of the data were lacking for the whole organism (in vivo) tests.

NORMAN guidance on suspect and non-target screening in environmental monitoring

“…Furthermore, due to the low viscosity originally seen as a "green" substitute for NPLC, SFC gained particular interest in environmental analysis as a complementary technique to RPLC to separate hydrophilic contaminants on polar stationary phases [122,123]. For certain substances with logD ow values close to 0, SFC can exhibit better sensitivity compared to RPLC due to high CO 2 content and low water content in the mobile phase which can improve ionisation in ESI [124] Although different strategies exist for coupling NPLC to mass spectrometry, this remains a challenging issue [125] and no application for the screening of environmental samples has been published so far. Classical NPLC employing aprotic solvents is incompatible with ESI, but could be coupled with APCI or atmospheric pressure photoionisation (APPI) sources.…”

ICP-MS As a Contributing Tool to Nontarget Screening (NTS) Analysis for Environmental Monitoring

“…Analytical separation includes reversed phase liquid chromatography (RP-LC), and gas chromatography (GC). To broaden the analytical platforms, other separation techniques such as hydrophilic lipophilic interaction chromatography (HILIC), ion chromatography (IC) , and supercritical fluid chromatography (SFC) , have also been employed to include the more polar compounds. Additional techniques like ion mobility and two-dimensional chromatography enhance separation and improve annotation, and identification of CECs. − Detection relies on high-resolution mass spectrometry (HRMS) for both suspect screening and NTS.…”

“…Additionally, it supports results obtained from other model prediction tools in LC-ESI-MS. 21,33 4.4. Mass Balance for Elemental Analysis to Support Analytical Workflows.…”

“…This is particularly relevant for providing quantitative NTS data that can be used in regulatory contexts demanding high accuracy and precision. Additionally, it supports results obtained from other model prediction tools in LC-ESI-MS. 21 , 33 …”