LC- and GC-QTOF-MS as Complementary Tools for a Comprehensive Micropollutant Analysis in Aquatic Systems

Magnetic solid phase extraction using Fe3O4@β-cyclodextrin–lipid bilayers as adsorbents followed by GC-QTOF-MS for the analysis of nine pesticides

A rapid method for the analysis of trace organochlorine pesticides in a complex matrix.

Organic contaminants in human breast milk identified by non-targeted analysis

Understanding the health implications of human exposure to mixtures of chemical contaminants is aided by analytical methods that can screen for a broad range of both expected and unexpected compounds. We performed a proof-of-concept analysis combining human breast milk, a biomonitoring matrix for determining contaminant exposure to mothers and infants, with a non-targeted method based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS). A total of 172 presumably anthropogenic halogenated compounds and non-halogenated cyclic and aromatic compounds were tentatively identified in breast milk from San Diego, California through mass spectral database searches. Forty of the compounds were prioritized for confirmation based on halogenation or 100% frequency of detection, and the identities of 30 were verified using authentic standards. Thirty-four (85%) of the prioritized contaminants are not typically monitored in breast milk surveys, and 31 (77%) are regulated in at least one market worldwide, indicating breast milk may be a useful biomonitoring matrix for non-targeted analysis and the assessment of human exposure to future emerging or undiscovered contaminants.

Suspect screening of plastic-related chemicals in northern pike (Esox lucius) from the St. Lawrence River, Canada

Environmental contaminant monitoring traditionally relies on targeted analysis, and very few tools are currently available to monitor "unexpected" or "unknown" compounds. In the present study, a non-targeted workflow (suspect screening) was developed to investigate plastic-related chemicals and other environmental contaminants in a top predator freshwater fish species, the northern pike, from the St. Lawrence River, Canada. Samples were extracted using sonication-assisted liquid extraction and analyzed by high performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (HPLC-QTOF-MS). Ten bisphenol compounds were used to test the analytical performances of the method, and satisfactory results were obtained in terms of instrumental linearity (r² > 0.97), recoveries, (86.53-119.32%), inter-day precision and method detection limits. The non-targeted workflow data processing parameters were studied, and the peak height filters (peak filtering step) were found to influence significantly the capacity to detect and identify trace chemicals in pike muscle extracts. None of the ten bisphenol analogues were detected in pike extracts suggesting the absence of accumulation for these chemicals in pike muscle. However, the non-targeted workflow enabled the identification of diethyl phthalate (DEP) and perfluorooctanesulfonic acid (PFOS) in pike extracts. This approach thus can be also applied to various contaminants in other biological matrices and environmental samples.

A Data-Independent Methodology for the Structural Characterization of Microcystins and Anabaenopeptins Leading to the Identification of Four New Congeners

Toxin-producing cyanobacteria are responsible for the presence of hundreds of bioactive compounds in aquatic environments undergoing increasing eutrophication. The identification of cyanotoxins is still emerging, due to the great diversity of potential congeners, yet high-resolution mass spectrometry (HRMS) has the potential to deepen this knowledge in aquatic environments. In this study, high-throughput and sensitive on-line solid-phase extraction ultra-high performance liquid chromatography (SPE-UHPLC) coupled to HRMS was applied to a data-independent acquisition (DIA) workflow for the suspect screening of cyanopeptides, including microcystin and anabaenopeptin toxin classes. The unambiguous characterization of 11 uncommon cyanopeptides was possible using a characterization workflow through extensive analysis of fragmentation patterns. This method also allowed the characterization of four unknown cyanotoxins ([Leu1, Ser7] MC-HtyR, [Asp3]MC-RHar, AP731, and AP803). The quantification of 17 common cyanotoxins along with the semi-quantification of the characterized uncommon cyanopeptides resulted with the identification of 23 different cyanotoxins in 12 lakes in Canada, United Kingdom and France. The concentrations of the compounds varied between 39 and 41,000 ng L-1. To our knowledge, this is the first DIA method applied for the suspect screening of two families of cyanopeptides simultaneously. Moreover, this study shows the great diversity of cyanotoxins in lake water cyanobacterial blooms, a growing concern in aquatic systems.

Assessment of gas chromatography time-of-flight mass spectrometry for the screening of semi-volatile compounds in indoor dust

Indoor dust contains a complex mixture of anthropogenic and synthetic compounds closely related to dermal and respiratory diseases. Target methods have been developed for the quantification of distinct groups of substances in dust samples; however, the comprehensive characterization of the different species existing in this matrix remains a challenging issue. Herein, we assess the performance of gas chromatography (GC) time-of-flight mass spectrometry (TOF-MS), using electron ionization (EI), for the screening of compounds present in indoor dust. Samples are processed by pressurized-liquid extraction (PLE) before GC-EI-TOF-MS analysis. The study proposes a data mining workflow for the non-target identification of species contained in dust extracts, aided by preliminary comparison with nominal resolution EI-MS spectra in the NIST17 library. The possibilities, and the limitations, of the above approach are discussed and the identities of >75 compounds are confirmed by comparison with authentic standards in dust from indoor environments. Some species, such as indigo, phthalic anhydride, 2,4-toluene di-isocyanate, phthalimide, certain UV absorbers and octyl isothiazolinone, identified in this research, have not been previously considered in target methods dealing with dust analysis. The study also evaluates two different algorithms for the suspected-target screening of dust extracts using a customized library of accurate EI-MS spectra. Finally, a semi-quantitative estimation of the range of concentrations for a group of 44 pollutants in a set of 27 dust samples is provided.

Nontarget analysis: A new tool for the evaluation of wastewater processes

Strategies to determine the removal efficiency of micropollutants in wastewater treatment plants (WWTPs) are widely discussed. Especially the evaluation of the potential benefit of further advanced treatment steps such as an additional tertiary treatment based on ozonation or activated carbon have come into focus. Such evaluation strategies are often based on the removal behavior of known micropollutants via target or suspected analysis. The utilization of nontarget analysis is considered to lead to a more comprehensive picture as also unknown or not expected micropollutants are analyzed. Here, the results of an evaluation via target and nontarget analysis were compared for biological treatment (BT) processes of eleven full-scale WWTPs and three different post-treatments (PTs): one sand filter (SF) and two granular activated carbon (GAC) filters. The similarity of the determined removals from target and nontarget analysis of the BTs increased significantly by excluding easily degradable "features" from the nontarget evaluation. A similar ranking of the removal trends for the BTs could also be achieved by comparing this new subset of nontarget features with a set of nine readily to moderately biodegradable micropollutants. This observation suggests that a performance ranking of BTs based either on target or nontarget analysis is plausible. In contrast to the BTs, the evaluation of the three PTs revealed that the difference of feature removal between SF and the two GACs was small, but large for the target analytes with substantially higher removal effciencies for the GACs compared to the SF. In addition to the removal behavior, the nontarget analysis provided further information about the number and quantity of transformation products (TPs) in the effluent from the BTs. For all BTs more than half (55-67%) of the features detected in the effluent were not found in the influent. A comparable proportion of TPs was also detected after GAC and sand filtration due to their microbial activities.

Bi-Directional Learning: Identifying Contaminants on the Yurok Indian Reservation

The Yurok Tribe partnered with the University of California Davis (UC Davis) Superfund Research Program to identify and address contaminants in the Klamath watershed that may be impairing human and ecosystem health. We draw on a community-based participatory research approach that begins with community concerns, includes shared duties across the research process, and collaborative interpretation of results. A primary challenge facing University and Tribal researchers on this project is the complexity of the relationship(s) between the identity and concentrations of contaminants and the diversity of illnesses plaguing community members. The framework of bi-directional learning includes Yurok-led river sampling, Yurok traditional ecological knowledge, University lab analysis, and collaborative interpretation of results. Yurok staff and community members share their unique exposure pathways, their knowledge of the landscape, their past scientific studies, and the history of landscape management, and University researchers use both specific and broad scope chemical screening techniques to attempt to identify contaminants and their sources. Both university and tribal knowledge are crucial to understanding the relationship between human and environmental health. This paper examines University and Tribal researchers' shared learning, progress, and challenges at the end of the second year of a five-year Superfund Research Program (SRP) grant to identify and remediate toxins in the lower Klamath River watershed. Our water quality research is framed within a larger question of how to best build university-Tribal collaboration to address contamination and associated human health impacts.

Suspect screening analysis of the occurrence and removal of micropollutants by GC-QTOF MS during wastewater treatment processes

The presence of micropollutants in wastewater treatment plant (WWTP) poses potential risks to the aquatic system and human health. This study comprehensively characterized the presence, elimination, and transformation of micropollutants in the WWTP using the suspect screening approaches by employing the gas chromatography coupled with quadrupole time-of-flight mass spectrometry. Overall, 5724 features were identified in influent, while only 3418 features existed in effluents. Hierarchical cluster analysis (HCA) was used to group features based on intensity profiles to investigate the behavior and fate of detected features. Four representative trends were defined with the corresponding features. Among 117 compounds identified during the treatment process, there were 99 compounds in influent, 10 biological transformation products (TPs), 3 ozone TPs, and 5 ultraviolet TPs. Furthermore, the removal efficiencies for the detected compounds were determined. The study findings highlight the importance of the removal of emerging pollutants and TPs such as fipronil, fipronil sulfide, and fipronil sulfone.

Understanding the bioavailability of pyrethroids in the aquatic environment using chemical approaches

Pyrethroids are a class of commonly used insecticides and are ubiquitous in the aquatic environment in various regions. Aquatic toxicity of pyrethroids was often overestimated when using conventional bulk chemical concentrations because of their strong hydrophobicity. Over the last two decades, bioavailability has been recognized and applied to refine the assessment of ecotoxicological effects of pyrethroids. This review focuses on recent advances in the bioavailability of pyrethroids, specifically in the aquatic environment. We summarize the development of passive sampling and Tenax extraction methods for assessing the bioavailability of pyrethroids. Factors affecting the bioavailability of pyrethroids, including physicochemical properties of pyrethroids, and quality and quantity of organic matter, were overviewed. Various applications of bioavailability on the assessment of bioaccumulation and acute toxicity of pyrethroids were also discussed. The final section of this review highlights future directions of research, including development of standardized protocols for measurement of bioavailability, establishment of bioavailability-based toxicity benchmarks and water/sediment quality criteria, and incorporation of bioavailability into future risk assessment and management actions.

Analyzing a broader spectrum of endocrine active organic contaminants in sewage sludge with high resolution LC-QTOF-MS suspect screening and QSAR toxicity prediction

Endocrine active contaminants (EACs) in environmental samples can pose a range of toxicological threats to ecosystems, especially through their impacts on reproductive pathways mediated by the estrogen receptor. The physicochemical properties of known organic EACs vary greatly and typically require different sample preparation techniques to identify different classes of compounds. EAC sources are similarly diverse, including both endogenous compounds and anthropogenic chemicals found in personal care products, pharmaceuticals, and their transformation products, which are often disposed of to sewers at their end of use. Looking for EACs in sewage sludge proposes a bottom-up, or end-of-use and treatment approach to discover environmentally relevant EACs, since many EACs accumulate in sludges even after application of robust wastewater treatment processes. This study demonstrates an extraction and analytical method capable of detecting a broad spectrum of known and suspected EACs via High Resolution Liquid Chromatography Quadropole Time-of-Flight Mass Spectrometry (LC-QTOF-MS) suspect screening of fourteen California sewage sludge samples. Spike-recovery experiments were performed using twelve carefully selected surrogates to assess different extraction solvents, sample weights, extraction pH values, procedures for combining extracts with different extraction pH's, and solid phase extraction cartridges. Using LC-QTOF-MS, identifications of several other organic compounds in the samples were made, a goal unachievable with unit resolution mass spectrometry. Suspect screening of California sludge samples discovered 118 compounds including hormones, pharmaceuticals, phosphate flame retardants, recreational drugs, antimicrobials, and pesticides. Additionally, 22 of these identified compounds are predicted to interfere with estrogen receptors or other reproductive/developmental pathways based on the VEGA QSAR toxicity prediction model.

Expanding phytoremediation to the realms of known and unknown organic chemicals of concern

Recent advancements in analytical chemistry and data analyses via high-resolution mass spectrometry (HRMS) are evolving scientific understanding of the potential totality of organic chemical exposure and pollutant risk. This review addresses the importance of HRMS approaches, namely suspect screening and nontarget chemical analyses, to the realm of phytoremediation. These analytical approaches are not without caveats and constraints, but they provide an opportunity to understand in greater totality how plant-based technologies contribute, mitigate, and reduce organic chemical exposure across scales of experimental and system-level studies. These analytical tools can enlighten the complexity and efficacy of plant-contaminant system design and expand our understanding of biogenic and anthropogenic chemicals at work in phytoremediation systems. Advances in data analytics from biological sciences, such as metabolomics, are crucial to HRMS analysis. This review provides an overview of targeted, suspect screening, and nontarget HRMS approaches, summarizes the expanding knowledge of regulated and unregulated organic chemicals in the environment, addresses requisite HRMS instrumentation, analysis cost, uncertainty, and data processing techniques, and offers potential bridges of HRMS analyses to phytoremediation research and application.

Comprehensive investigation of pesticides in Brazilian surface water by high resolution mass spectrometry screening and gas chromatography-mass spectrometry quantitative analysis

In this work, a comprehensive investigation on the occurrence of pesticides in the Paraná 3 hydrographic basin of Paraná State, Brazil, was made by application of wide-scope screening based on ultra-high performance liquid chromatography (LC) and gas chromatography (GC) both coupled to quadrupole time-of-flight mass spectrometry (QTOF MS). The use of two complementary techniques, such as GC-QTOF MS and LC-QTOF MS, allowed screening a large number of compounds with different polarity and volatility. This screening approach was applied to 17 samples, enabling the detection of fifty-two pesticides and six metabolites. In a second step, an specific research was made on the herbicide atrazine, one of the most frequent compounds in samples, and its major transformation products (TPs), which were quantitatively analyzed by dispersive liquid-liquid microextraction (DLLME) followed by GC-MS measurement. Twenty-one agricultural streams from the Paraná 3 hydrographic basin were sampled twice in 2017, each time along six successive weeks. Additional samples were also collected after rain events exceeding 10 mm. In total, 407 samples were quantitatively analyzed by DLLME/GC-MS. Atrazine concentrations did not exceed the maximum permitted concentration of 2 μg L^-1 according to Brazilian legislation, and only one surface water sample, collected after precipitation events, was slightly above this value (2.89 μg L^-1). The maximum concentrations for the TPs desethylatrazine and deisopropylatrazine were 0.80 and 1.22 μg L^-1, respectively. Based on the quantification results, a map was produced showing the occurrence of atrazine and its TPs in the area under study. This is the first time that the presence of agrochemicals is evaluated in the Paraná 3 hydrographic basin.

Comprehensive Target Analysis for 484 Organic Micropollutants in Environmental Waters by the Combination of Tandem Solid-Phase Extraction and Quadrupole Time-of-Flight Mass Spectrometry with Sequential Window Acquisition of All Theoretical Fragment-Ion Spectra Acquisition

There are many thousands of chemicals in use for a wide range of purposes, and highly efficient analytical methods are required to monitor them for protection of the environment. In order to cope with this difficult task we developed a novel, comprehensive method for 484 substances in water samples. In this method target chemicals were extracted by tandem SPE and then determined by LC-QTOF-MS-SWATH. Targets were unambiguously identified using retention times, accurate masses of a precursor and two product ions, their ion ratios, and accurate MS/MS spectrum. Quantitation was achieved by the internal standard method using a precursor ion. Results of recovery tests at two concentrations (50 and 500 ng L^-1) showed average recoveries of 87.5% and 87.0% (RSD, 9.1% and 9.4%), respectively. Limits of detection of one-half of the targets were below 1.0 ng L^-1. The method was applied to the influent and effluent of a sewage treatment plant, and around 100 chemicals were detected. Results of examination on matrix effects using their extracts spiked with 209 pesticides showed that the ratios of detected amounts between the extracts and the standard solution were 89.8% (influent) and 91.7% (effluent), respectively. In addition, investigation on the stability of calibration curves by injecting the same standards for 1 year showed that their quantitative results did not change; average accuracy was 103.3% (RSD, 10.0%), indicating that the calibration curves can be used for an extended period of time without calibration, and quantitative retrospective analysis can be done after creating calibration curves for new targets.

Impact of method parameters on the performance of suspect screening for the identification of trace organic contaminants in surface waters

The performance of a suspect screening method to detect diverse small-molecule trace organic contaminants (TOCs) was systematically evaluated using a set of 39 model compounds. Experiments showed that ionization efficiency, ion transfer parameters, and chromatography could affect the detection of TOCs. As expected, compounds with low ionization yields and poorly retained compounds in chromatographic columns are more difficult to identify in the samples at environmental concentrations. Similarly, TOCs with large deviations from the average mass of the compounds screened were not transmitted efficiently in the mass spectrometer thus negatively affecting their detection. The suspect screening method was validated in terms of recovery and limits of identification of the model compounds using three different types of solid-phase extraction cartridges (reversed phase with polar groups, mixed-mode anion exchange, and mixed mode cation exchange). Experiments showed that more than two-thirds of the model compounds had recoveries >75% with each of the three cartridges, and comparison of limits of identification showed that more than one-half of the model compounds could be identified at concentrations between 6 and 100 ng L−1. However, it was observed that the amount of co-extracted compounds was higher in mixed-mode ion exchangers compared with the reversed-phase cartridge. Application of the suspect screening method using the three different cartridges to surface water samples showed that between 0 to 3% of the positive matches found by the peak identification algorithm were classified as probable structures. Solutions to improve suspect screening of TOCs are proposed and discussed.

Exposure Assessment For Air-To-Skin Uptake of Semivolatile Organic Compounds (SVOCs) Indoors

Semivolatile organic compounds (SVOCs) are ubiquitous in the indoor environment and a priority for exposure assessment because of the environmental health concerns that they pose. Direct air-to-skin dermal uptake has been shown to be comparable to the inhalation intake for compounds with certain chemical properties. In this study, we aim to further understand the transport of these types of chemicals through the skin, specifically through the stratum corneum (SC). Our assessment is based on collecting three sequential forehead skin wipes, each hypothesized to remove pollutants from successively deeper skin layers, and using these wipe analyses to determine the skin concentration profiles. The removal of SVOCs with repeated wipes reveals the concentration profiles with depth and provides a way to characterize penetration efficiency and potential transfer to blood circulation. We used a diffusion model applied to surface skin to simulate concentration profiles of SVOCs and compared them with the measured values. We found that two phthalates, dimethyl and diethyl phthalates, penetrate deeper into skin with similar exposure compared to other phthalates and targeted SVOCs, an observation supported by the model results as well. We also report the presence of statistically significant declining patterns with skin depth for most SVOCs, indicating that their diffusion through the SC is relevant and eventually can reach the blood vessels in the vascularized dermis. Finally, using a nontarget approach, we identified skin oxidation products, linked to respiratory irritation symptoms, formed from the reaction between ozone and squalene.

Developmental exposure to environmentally relevant concentrations of bifenthrin alters transcription of mTOR and ryanodine receptor-dependent signaling molecules and impairs predator avoidance behavior across early life stages in inland silversides (Menidia beryllina)

Altered transcription of calcium-dependent signaling cascades involving the ryanodine receptor (RyR) and mechanistic target of rapamycin (mTOR) in response to environmental exposures have been described in model vertebrates, including zebrafish, while the relevance for wild fishes remains unknown. To address this knowledge gap, we exposed the euryhaline model species Menidia beryllina (inland silversides) to the insecticide bifenthrin, a known modulator of calcium signaling. The main objectives of this study were to determine: (1) whether exposure of developing silversides to environmentally relevant concentrations of bifenthrin alters their behavior; and (2) whether behavioral changes correlate with altered expression of genes involved in RyR and mTOR-dependent signaling pathways. At six hours post fertilization (hpf), inland silversides were exposed to bifenthrin at 3, 27 and 122 ng/L until 7 days post fertilization (dpf, larvae hatched at 6dpf), followed by a 14-day recovery period in uncontaminated water. Transcriptional responses were measured at 5, 7 and 21 dpf; locomotor behavior following external stimuli and response to an olfactory predator cue were assessed at 7 and 21 dpf. Bifenthrin elicited significant non-monotonic transcriptional responses in the majority of genes examined at 5 dpf and at 21 dpf. Bifenthrin also significantly altered predator avoidance behavior via olfactory mechanisms with main effects identified for animals exposed to 3 and 27 ng/L. Behavioral effects were not detected in response to visual stimuli during acute exposure, but were significant in the predator-cue assessment following the recovery period, suggesting delayed and long-term effects of early developmental exposures to bifenthrin. Our findings demonstrate that at picomolar (pM) concentrations, which are often not represented in ecotoxicological studies, bifenthrin perturbs early development of inland silversides. These developmental impacts are manifested behaviorally at later life stages, specifically as altered patterns of predator avoidance behavior, which have been correlated with population decline. Collectively, these data suggest that bifenthrin may be negatively impacting wild fish populations.

Perspectives on Liquid Chromatography-High-Resolution Mass Spectrometry for Pesticide Screening in Foods

This perspective discusses the use of liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) for multiresidue analysis of pesticides in foods and agricultural commodities. HRMS has the important distinction and advantage of mass-resolving power and, therefore, requires different concepts, experiments, and guidance for screening, identification, and quantitation of pesticides in complex food matrices over triple quadrupole mass spectrometry. HRMS approaches for pesticide screening, including full-scan experiments in conjunction with tandem mass spectrometry (MS/MS) experiments, are described. This approach results in the generation of chromatographic retention times and high-resolution mass spectra with accurate mass measurements that can be used to create compound databases. New data processing tools can create an efficient and optimized screening approach that can speed the analysis and identification of compounds, reduce the need for chemical standards, and harmonize pesticide analytical procedures.

Using High-Resolution Mass Spectrometry to Identify Organic Contaminants Linked to Urban Stormwater Mortality Syndrome in Coho Salmon

Urban stormwater is a major threat to ecological health, causing a range of adverse, mostly sublethal effects. In western North America, urban runoff is acutely lethal to adult coho salmon ( Oncorhynchus kisutch) that spawn each fall in freshwater creeks. Although the mortality syndrome is correlated to urbanization and attributed to road runoff contaminant(s), the causal agent(s) remain unknown. We applied high-resolution mass spectrometry to isolate a coho mortality chemical signature: a list of nontarget and identified features that co-occurred in waters lethal to coho spawners (road runoff from controlled exposures and urban receiving waters from two field observations of symptomatic coho). Hierarchical cluster analysis indicated that tire wear particle (TWP) leachates were most chemically similar to the waters with observed toxicity, relative to other vehicle-derived sources. Prominent road runoff contaminants in the signature included two groups of nitrogen-containing compounds derived from TWP, polyethylene glycols, octylphenol ethoxylates, and polypropylene glycols. A (methoxymethyl)melamine compound family, previously unreported in North America, was detected in road runoff and urban creeks at concentrations up to ∼9 and ∼0.3 μg/L, respectively. The results indicate TWPs are an under-appreciated contaminant source in urban watersheds and should be prioritized for fate and toxicity assessment.

Contaminant exposure effects in a changing climate: how multiple stressors can multiply exposure effects in the amphipod Hyalella azteca

Global climate change (GCC) is likely to intensify the synergistic effects between altered physicochemical parameters [of changing habitats] and other anthropogenic threats, such as water pollution, posing increased risks to aquatic biodiversity. As such, it is critical to understand how organisms will respond to changes in water temperature and salinity in the presence of contaminants. We exposed the epibenthic amphipod Hyalella azteca to a 3 × 3 factorial treatment design of three temperatures and three salinities ranging from 12 to 18 °C and 0 to 8 parts per thousand (ppt), respectively, in combination with a low-level environmentally relevant concentration of the pyrethroid insecticide bifenthrin (1 ng/L). Effects on survival and swimming behavior were evaluated after 96 h exposure. Transcription of a select suite of genes was monitored at 24, 48, and 96 h using quantitative polymerase chain reaction (qPCR). Our results not only demonstrate that the changes in salinity and temperature result in negative effects to invertebrate survival, behavior, and gene response, but that the effects were significantly more pronounced in the presence of bifenthrin. This is particularly important since greater thermal fluctuations, changes in timing and extent of glacial melt, and changes in precipitation, could result in H. azteca experiencing lower temperatures at times that coincide with increased spraying of pyrethroids. These environmentally relevant exposures using the standard test species H. azteca provide essential information for understanding effects caused by GCC in conjunction with increasing pesticide use, further highlighting the need to incorporate GCC impacts into risk assessments of contaminants of concern.

Suspect Screening and Regulatory Databases: A Powerful Combination To Identify Emerging Micropollutants

This study demonstrates that regulatory databases combined with the latest advances in high resolution mass spectrometry (HRMS) can be efficiently used to prioritize and identify new, potentially hazardous pollutants being discharged into the aquatic environment. Of the approximately 23000 chemicals registered in the database of the National Swedish Product Register, 160 potential organic micropollutants were prioritized through quantitative knowledge of market availability, quantity used, extent of use on the market, and predicted compartment-specific environmental exposure during usage. Advanced liquid chromatography (LC)-HRMS-based suspect screening strategies were used to search for the selected compounds in 24 h composite samples collected from the effluent of three major wastewater treatment plants (WWTPs) in Sweden. In total, 36 tentative identifications were successfully achieved, mostly for substances not previously considered by environmental scientists. Of these substances, 23 were further confirmed with reference standards, showing the efficiency of combining a systematic prioritization strategy based on a regulatory database and a suspect-screening approach. These findings show that close collaboration between scientists and regulatory authorities is a promising way forward for enhancing identification rates of emerging pollutants and expanding knowledge on the occurrence of potentially hazardous substances in the environment.

Recent trends in water analysis triggering future monitoring of organic micropollutants

Water analysis has been an important area since the beginning of analytical chemistry. The focus though has shifted substantially: from minerals and the main constituents of water in the time of Carl Remigius Fresenius to a multitude of, in particular, organic compounds at concentrations down to the sub-nanogram per liter level nowadays. This was possible only because of numerous innovations in instrumentation in recent decades, drivers of which are briefly discussed. In addition to the high demands on sensitivity, high throughput by automation and short analysis times are major requirements. In this article, some recent developments in the chemical analysis of organic micropollutants (OMPs) are presented. These include the analysis of priority pollutants in whole water samples, extension of the analytical window, in particular to encompass highly polar compounds, the trend toward more than one separation dimension before mass spectrometric detection, and ways of coping with unknown analytes by suspect and nontarget screening approaches involving high-resolution mass spectrometry. Furthermore, beyond gathering reliable concentration data for many OMPs, the question of the relevance of such data for the aquatic system under scrutiny is becoming ever more important. To that end, effect-based analytics can be used and may become part of future routine monitoring, mostly with a focus on adverse effects of OMPs in specific test systems mimicking environmental impacts. Despite advances in the field of water analysis in recent years, there are still many challenges for further analytical research. Graphical abstract Recent trends in water analysis of organic micropollutants that open new opportunities in future water monitoring. HRMS high-resolution mass spectrometry, PMOC persistent mobile organic compounds.

Household Dust as a Repository of Chemical Accumulation: New Insights from a Comprehensive High-Resolution Mass Spectrometric Study

Chemical exposure in household dust poses potential risks to human health but has been studied incompletely thus far. Most analytical studies have focused on one or several compound classes, with analysis performed by either liquid or gas chromatography coupled with mass spectrometry (LC-MS or GC-MS). However, a comprehensive investigation of individual dust samples is missing. The present study comprehensively characterizes chemicals in dust by applying a combination of target, suspect, and nontarget screening approaches using both LC and GC with quadrupole time-of-flight (Q/TOF) MS. First, the extraction method was optimized to streamline detection of LC-Q/TOF and GC-Q/TOF amenable compounds and was successfully validated with over 100 target compounds. Nontarget screening with GC-Q/TOF was done by spectral deconvolution followed by a library search. Suspect screening by LC-Q/TOF was carried out with an accurate mass spectral library. Finally, LC-Q/TOF nontarget screening was carried out by extracting molecular features, acquiring tandem mass spectrometric (MS/MS) spectra, and performing compound identification by use of in silico fragmentation software tools. In total, 271 chemicals could be detected in 38 dust samples, 163 of which could be unambiguously confirmed by a reference standard. Many of them, such as the plastic leachable 7,9-di- tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione (CAS 82304-66-3) and three organofluorine compounds, are of emerging concern and their presence in dust has been underestimated. Advantages and drawbacks of the different approaches and analytical instruments are critically discussed.

Using Mutations for Pesticide Resistance to Identify the Cause of Toxicity in Environmental Samples

Traditional Toxicity Identification Evaluations (TIE) are applied to identify causal agents in complex environmental samples showing toxicity and rely upon physical or chemical manipulation of samples. However, mutations conferring toxicant resistance provide the opportunity for a novel biologically based TIE. Populations within the Hyalella azteca complex from pesticide-affected waterways were 2 and 3 orders of magnitude more resistant to the pyrethroid cyfluthrin and the organophosphate chlorpyrifos, respectively, than laboratory-cultured H. azteca widely used for toxicity testing. Three resistant populations, as well as laboratory-cultured, nonresistant H. azteca, were exposed to urban and agricultural runoff. Every sample causing death or paralysis in the nonresistant individuals had no effect on pyrethroid-resistant individuals, providing strong evidence that a pyrethroid was the responsible toxicant. The lack of toxicity to chlorpyrifos-sensitive, but pyrethroid-resistant, individuals suggested chlorpyrifos was not a likely toxicant, a hypothesis supported by chemical analysis. Since these mutations that confer resistance to pesticides are highly specific, toxicity to wild-type, but not resistant animals, provides powerful evidence of causality. It may be possible to identify strains resistant to even a wider variety of toxicants, further extending the potential use of this biologically based TIE technique beyond the pyrethroid and organophosphate-resistant strains currently available.

Recent applications of gas chromatography with high-resolution mass spectrometry

Gas chromatography coupled to high-resolution mass spectrometry is a powerful analytical method that combines excellent separation power of gas chromatography with improved identification based on an accurate mass measurement. These features designate gas chromatography with high-resolution mass spectrometry as the first choice for identification and structure elucidation of unknown volatile and semi-volatile organic compounds. Gas chromatography with high-resolution mass spectrometry quantitative analyses was previously focused on the determination of dioxins and related compounds using magnetic sector type analyzers, a standing requirement of many international standards. The introduction of a quadrupole high-resolution time-of-flight mass analyzer broadened interest in this method and novel applications were developed, especially for multi-target screening purposes. This review is focused on the development and the most interesting applications of gas chromatography coupled to high-resolution mass spectrometry towards analysis of environmental matrices, biological fluids, and food safety since 2010. The main attention is paid to various approaches and applications of gas chromatography coupled to high-resolution mass spectrometry for non-target screening to identify contaminants and to characterize the chemical composition of environmental, food, and biological samples. The most interesting quantitative applications, where a significant contribution of gas chromatography with high-resolution mass spectrometry over the currently used methods is expected, will be discussed as well.