Narrowing the analytical gap for water-soluble polymers: A novel trace-analytical method and first quantitative occurrence data for polyethylene oxide in surface and wastewater.

Water-soluble polymers (WSPs) like polyethylene oxide (PEO) have annual production volumes ranging from thousands to millions of tonnes and are used in a wide variety of applications that enable a release into the aquatic environment. Despite these facts, a lack of quantitative trace-analytical methods for WSPs prevents the comprehensive study of their environmental occurrence. Here, size exclusion chromatography was hyphenated with electrospray ionization high-resolution mass spectrometry. An all-ion fragmentation approach for the formation of diagnostic fragments independent of molecular weight, charge state, and ion species was used to quantify PEO and its derivatives in wastewater treatment plants (WWTPs) and surface water samples. Despite its inherent biodegradability, PEO concentrations found in the samples analysed ranged from 1 µg/L) and reached up to 20 µg/L (effluent) and 400 µg/L (influent) for WWTPs. A substantial shift in molecular weight ranges was observed between influent and effluent, pointing towards a molecular weight fraction between 1.3 and 4 kDa being dominant in the effluent. Due to an assumed size exclusion during sample enrichment, information on the MW-distribution of PEO is limited to MW < 55 kDa. The high concentrations widely detected for a readily biodegradable WSP such as PEO, raise strong concerns about the occurrence and fate of recalcitrant WSPs in the aquatic environment. The method presented herein may provide the tools necessary to assess the burden of these high production volume chemicals and the risk they may pose.

Making waves: Water-soluble polymers in the aquatic environment: An overlooked class of synthetic polymers?

Synthetic polymers have been one of the defining environmental topics of the last decade. Synthetic polymers in the environment are usually classified by their size. They encompass the widely discussed size fractions of macroplastic, microplastic, and nanoplastic. Water-soluble polymers (WSPs), however, are mostly absent in this discussion. In this paper, we argue that WSPs are produced in large quantities and have many applications that facilitate a discharge into the environment, where their fate and impact remain mostly unclear. We argue that there are yet no suitable analytical methods for the quantification of WSPs in environmental matrices and propose an analytical method that utilizes size exclusion chromatography - mass spectrometry to detect and potentially also quantify WSPs through specific fragments generated by in-source fragmentation. With the detection of polyethylene glycol in a wastewater treatment plant effluent and a surface water sample we provide a first prove of principle for the applicability of this novel analytical approach to WSPs. Ultimately, we conclude that WSPs are currently in a similar position as MP were in the advent of their investigation: We know of an environmental contamination but are uncertain of its extent and impact and still lack the tools to investigate them thoroughly.