Sample Preparation, Nontarget and Suspect Screening of Persistent and Mobile Organic Contaminants in Water

Persistent and mobile organic contaminants (PMOCs) are a class of small molecule contaminants and transformation products whose high polarity enables them to persist in aquatic environments. These contaminants enter waterways by way of household, industrial, and agricultural waste, encompassing many use classes such as pharmaceuticals, pesticides, industrial chemicals, and short- and ultra-short-chain PFAS. Due to their hydrophilicity, PMOCs do not sorb well to sediments, soils or biomaterials, allowing them to slip through common water treatment and occur in treated effluent. In addition to this protection gap, high polarity makes these compounds difficult to analyze by conventional means, posing an analytical gap and leaving PMOCs under-monitored, understudied, and undiscovered. To enable PMOC analysis, an enrichment protocol utilizing evaporative concentration was developed and assessed for recovery for 25 model PMOC standards, including known PMOCs metformin, melamine, and trifluoroacetic acid. These methods were optimized for enrichment of PMOCs in drinking water and surface water samples for high recovery versus conventional methods. Targeted zwitterionic hydrophilic interaction liquid chromatography methods were developed for model standards and paired with electrospray ionization high resolution mass spectrometry using an Orbitrap Exploris 240. These methods were then expanded to suspect and nontarget analysis of PMOCs in drinking and surface water, revealing unmonitored organic contaminants. This study reinforces that conventional means of enrichment and chromatographic separation are often not amenable to highly polar analytes and tailored analytical methods are necessary to perform broad screening of this emerging class of contaminants.