Seawater analysis by ambient mass-spectrometry-based seaomics

Abstract

Abstract. An analytical method coupled to multivariate statistical analysis was developed based on transmission-mode direct analysis in real-time quadrupole time-of-flight mass spectrometry (TM-DART-QTOF-MS) to interrogate lipophilic compounds in seawater samples without the need for desalinization. An untargeted metabolomics approach is addressed here as seaomics and was successfully implemented to discriminate the sea surface microlayer (SML) from the underlying water (ULW) samples (n=22, 10 paired samples) collected during a field campaign at the Cabo Verde islands during September–October 2017. A panel of 11 ionic species detected in all samples allowed sample class discrimination by means of supervised multivariate statistical models. Tentative identification of the species enriched in the SML samples suggests that fatty alcohols, halogenated compounds, and oxygenated boron-containing organic compounds are available at the surface for air–water transfer processes. A subset of SML samples (n=5) were subjected to on-site experiments during the campaign by using a lab-to-field approach to test their secondary organic aerosol (SOA) formation potency. The results from these experiments and the analytical seaomics strategy provide a proof of a concept that can be used for an approach to identifying organic molecules involved in aerosol formation processes at the air–water interface.

Tidy-Direct-to-MS: An Open-Source Data-Processing Pipeline for Direct Mass Spectrometry-Based Metabolomics Experiments

“…These comparisons demonstrate that the majority of the results and features detected by both tools are in agreement, and that Tidy-Directto-MS correctly processed the DART-MS data set. The Tidy-Direct-to-MS pipeline was also able to detect the discriminant features reported by Zabalegui et al 17 Furthermore, an interbatch drift correction (see Batch Correction section) was performed after feature detection and processing with the Tidy-Direct-to-MS pipeline. A time dependent intensity drift was successfully corrected using the pooled QC samples, yielding mean abundance shift factors of between 0.75 and 1.32 across the acquisition batches.…”

“…The seaomics data set from Zabalegui et al 17 was processed with the developed pipeline, to showcase the capabilities of the tool. While this work focused on how to apply the tool in a particular experiment, the proposed framework is still general for other direct-to-MS-based metabolomics studies.…”

“…That study investigated seawater samples collected at the Cape Verde Islands with two different water collection methods from the sea surface microlayer (SML) and 1 m depth (underlying water, ULW). Samples were lyophilized, reconstituted, and subsequently analyzed with TM-DART-MS (the interested reader is referred to the publication 17 for detailed information).…”

“…Results from raw data processed using the vendor tools Progenesis Bridge (Waters Corp., Milford, USA) and Progenesis QI (Waters Corp., Milford, USA) (further details are provided in Zabalegui et al 17 ) were compared with those obtained from the same raw data processed with the newly developed Tidy-Direct-to-MS pipeline. Data processing parameters of the pipeline were optimized with the semiautomated method before selecting a final set.…”

Rapid Screening and Quantification of PFAS Enabled by SPME-DART-MS

“…Conventionally, analysis of PFAS is performed utilizing LC-MS/MS techniques. ,− While these methods are highly sensitive and allow effective separation of isomeric species and quantification, alternative techniques such as direct ambient mass spectrometry (AMS) can enable higher sample throughput, which is ideal for screening purposes . The plasma-based AMS technique direct analysis in real time (DART) enables high throughput screening and quantification of various classes of molecules for both positively and negatively ionized species. − Furthermore, there has been recent interest in the DART analysis of PFAS, with results from Cody and Maleknia demonstrating robust ng/L level quantification of PFOA and the screening of various other PFAS such as PFOS, using coated glass capillaries (CGCs) with octadecylamine as an extraction phase for PFAS . In fact, many developed AMS methods benefit from analyte preconcentration prior to instrumental analysis. , Previous work from our research group has demonstrated the use of solid phase microextraction (SPME) devices composed of hydrophilic–lipophilic balance–weak anion exchange particles embedded in polyacrylonitrile (HLB-WAX/PAN) as an ideal strategy for the preconcentration of multiple classes of PFAS, allowing sub-ng/L detection when coupled with LC-MS/MS. , …”