Combination of different chromatographic and sampling modes for high-resolution mass spectrometric screening of organic microcontaminants in water

Nitrophenols in the environment: An update on pretreatment and analysis techniques since 2017

Nitrophenols, a versatile intermediate, have been widely used in leather, medicine, chemical synthesis, and other fields. Because these components are widely applied, they can enter the environment through various routes, leading to many hazards and toxicities. There has been a recent surge in the development of simple, rapid, environmentally friendly, and effective techniques for determining these environmental pollutants. This review provides a comprehensive overview of the latest research progress on the pretreatment and analysis methods of nitrophenols since 2017, with a focus on environmental samples. Pretreatment methods include liquid-liquid extraction, solid-phase extraction, dispersive extraction, and microextraction methods. Analysis methods mainly include liquid chromatography-based methods, gas chromatography-based methods, supercritical fluid chromatography. In addition, this review also discusses and compares the advantages/disadvantages and development prospects of different pretreatment and analysis methods to provide a reference for further research.

Screening of organic chemicals associated to virgin low-density polyethylene microplastic pellets exposed to the Mediterranean Sea environment by combining gas chromatography and liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry

In this work, organic chemicals associated with microplastics (MPs) exposed to a coastal anthropogenized environment for up to eight weeks have been screened for, in order to discern the (de)sorption dynamics of chemicals in the marine ecosystem. Low-density polyethylene (LDPE) pellets were studied since they represent primary MPs used by the plastic industry and a relevant input of MPs into the oceans. To maximize the coverage of chemicals that could be detected, both liquid and gas chromatography coupled to quadrupole-time-of-flight (GC-QTOF and LC-QTOF, respectively) were used. In the case of LC-QTOF, an electrospray ionization source was employed, and the compounds were investigated by combining suspect and non-target screening workflows. The GC-QTOF was equipped with an electron ionization source and compounds were screened in raw and derivatized (silylated) extracts by deconvolution and contrast to high- and low-resolution libraries. A total of 50 compounds of multifarious classes were tentatively identified. Among them, melamine and 2-ethylhexyl salicylate (EHS) were detected in the original MPs but were rapidly desorbed. Melamine was completely released into the marine environment, while EHS was partly released but a portion remained bound to the MPs. On the other hand, many other chemicals of both anthropogenic (e.g. phenanthrene or benzophenone) and natural origin (e.g. betaine and several fatty acids) accumulated onto MPs over time. Quantification of 12 unequivocally identified chemicals resulted into a total concentration of 810 μg/kg after MPs exposure for 8 weeks.

Fluorescent sensor based on solid-phase extraction with negligible depletion: A proof-of-concept study with amines as analytes

This paper describes the development and proof-of-concept testing of an easy-to-use trace analysis technique, namely F-SPE, by coupling fluorescent sensor with solid phase extraction (SPE). F-SPE is a two-step methodology that concentrates an analyte from a liquid sample onto a fluorophore-modified membrane and measures the amount of analyte from the extent the extracted analyte quenches the emission of the fluorophore. By applying the principle of negligible depletion (ND) intrinsic to SPE, the procedure of F-SPE for analyzing a sample can be markedly simplified while maintaining the ability to detect analytes at low limits of detection (LOD). The merits of this approach are demonstrated by impregnating a SPE membrane with a perylene diimide (PDI) fluorophore, N,N'-di(nonyldecyl)-perylene-3,4,9,10-tetracarboxylic diimide (C9/9-PDI), for the low-level detection of organic amines (e.g., aniline) and amine-containing drugs (e.g., Kanamycin). The sensing mechanism is based on the donor-acceptor quenching of PDI by amines, which, when coupled with the concentrative nature of SPE, yields LODs for aniline and Kanamycin of 67 nM (∼6 ppb) and 32 nM (∼16 ppb), respectively.

Occurrence of organic pollutants in the River Itchen and River Test-two chalk streams in Southern England, UK

The River Itchen and River Test, two chalk streams in Southern England, are sites of special scientific interest. These ecosystems face a number of environmental pressures from anthropogenic inputs of organic pollutants. Hence, we investigated the occurrence of these chemicals within the two catchments. Spot water samples (1 L) were collected at nineteen sites along the catchment on two occasions (March and June 2019). Samples were extracted (HLB-L sorbent disks) and analysed using high-resolution liquid chromatography-quadrupole-time-of-flight mass spectrometry and gas chromatography-mass spectrometry. Compounds were identified against commercially available databases. Using this approach, we found 115 pharmaceutical and personal care products, 81 plant protection products and 35 industrial chemicals. This complex mixture of pollutants covered a range of physico-chemical properties and included priority substances in the EU Water Framework Directive or currently on the third Watch List. Both rivers had similar chemical profiles for both months. Herbicides and fungicides were dominant in the spring, whereas insecticides occurred more frequently in the summer. Point discharges from wastewater treatment plants were the main source of pharmaceutical and personal care products. Agricultural activities were the main contributor to the presence of plant protection products. The impact of these organic chemicals on the ecology, particularly on macroinvertebrate biodiversity, is unknown and warrants further investigation. Our suspect screening approach could guide future toxicological investigations to assess the environmental impacts of these diverse chemicals.

A Review on Polyethersulfone Membranes in Polar Organic Chemical Integrative Samplers: Preparation, Characterization and Innovation

The membranes in polar organic chemical integrative samplers (POCIS) enclose the receiving sorbent and protect it from coming into direct contact with the environmental matrix. They have a crucial role in extending the kinetic regime of contaminant uptake, by slowing down their diffusion between the water phase and the receiving phase. The drive to improve passive sampling requires membranes with better design and enhanced performances. In this review, the preparation of standard polyethersulfone (PES) membranes for POCIS is presented, as well as methods to evaluate their composition, morphology, structure, and performance. Generally, only supplier-related morphological and structural data are provided, such as membrane type, thickness, surface area, and pore diameter. The issues related to the use of PES membranes in POCIS applications are exposed. Finally, alternative membranes to PES in POCIS are also discussed, although no better membrane has yet been developed. This review highlights the urge for more membrane characterization details and a better comprehension of the mechanisms which underlay their behavior and performance, to improve membrane selection and optimize passive sampler development.

Pesticide fate during drinking water treatment determined through passive sampling combined with suspect screening and multivariate statistical analysis

Emerging contaminants such as polar pesticides pose a potential risk to human health due to their presence in drinking water. However, their occurrence and fate in drinking water treatment plants is poorly understood. In this study we use passive sampling coupled to suspect screening and multivariate analysis to describe pesticide fate throughout the treatment stream of an operational drinking water treatment plant. Chemcatcher^Ò passive sampling devices were deployed at sites (n = 6) positioned at all stages of the treatment stream during consecutive deployments (n = 20) over a twelve-month period. Sample extracts (n = 120) were analysed using high-resolution liquid chromatography-quadrupole-time-of-flight mass spectrometry and compounds identified against a commercially available database. A total of 58 pesticides and transformation products from different classes were detected. Statistical analysis of the qualitative screening data was performed to identify clusters of pesticides with similar fate during ozonation, granular activated carbon (GAC) filtration, and chlorination. The performance of each treatment process was investigated. Adsorption to GAC media was found to account for the greatest proportion of pesticide attenuation (average removal of 70% based on detection frequency), however, operational performance varied for certain pesticides during periods of episodic and sustained pollution. GAC breakthrough occurred for 21 compounds detected in the GAC filtrate. Eleven pesticides were found to occur in potable water following treatment. We developed a management plan containing controls, triggers, and responses, for five pesticides and a metabolite (atrazine, atrazine desethyl, DEET, dichlorobenzamide, metazachlor, and propyzamide) prioritised based on their current and future risk to treated water quality.

The study of polar emerging contaminants in seawater by passive sampling: A review

Emerging Contaminants (ECs) in marine waters include different classes of compounds, such as pharmaceuticals and personal care products, showing "emerging concern" related to the environment and human health. Their measurement in seawater is challenging mainly due to the low concentration levels and the possible matrix interferences. Mass spectrometry combined with chromatographic techniques represents the method of choice to study seawater ECs, due to its sensitivity and versatility. Nevertheless, these instrumental techniques have to be preceded by suitable sample collection and pre-treatment: passive sampling represents a powerful approach in this regard. The present review compiles the existing occurrence studies on passive sampling coupled to mass spectrometry for the monitoring of polar ECs in seawater and discusses the availability of calibration data that enabled quantitative estimations. A vast majority of the published studies carried out during the last two decades describe the use of integrative samplers, while applications of equilibrium samplers represent approximately 10%. The polar Chemcatcher was the first applied to marine waters, while the more sensitive Polar Organic Chemical Integrative Sampler rapidly became the most widely employed passive sampler. The organic Diffusive Gradients in Thin film technology is a recently introduced and promising device, due to its more reliable sampling rates. The best passive sampler selection for the monitoring of ECs in the marine environment as well as future research and development needs in this area are further discussed. On the instrumental side, combining passive sampling with high resolution mass spectrometry to better assess polar ECs is strongly advocated, despite the current challenges associated.

Non-target and suspect-screening analyses of hydroponic soybeans and passive samplers exposed to different watershed irrigation sources

Water scarcity increases the likelihood of irrigating food crops with municipal wastewater that may pose potential dietary risks of regulated and non-regulated organic chemical uptake to edible plant tissues. Only a few studies have used high resolution mass spectrometry (HRMS) to assess the uptake of chemicals of concern into food crops. This study used non-target and suspect-screening analyses to compare total chemical features, tentatively identified chemicals (TICs), and EPA ToxCast chemicals in soybean plants and passive samplers exposed to five different irrigation sources that were collected from an agricultural watershed during mild drought conditions. Secondary-treated municipal wastewater effluent, two surface waters, two ground waters, and deionized municipal tap water were used for two hydroponic experiments: soybean roots and shoots and Composite Integrative Passive Samplers (CIPS) harvested after fourteen days of exposure and soybeans after fifty-six days. CIPS were sealed in separate glass amber jars to evaluate their efficacy to mimic chemical features, TICs, and ToxCast chemical uptake in plant roots, shoots, and beans. Total soybean biomass and water use were greatest for tap water, municipal wastewater, and surface water downstream of the municipal wastewater facility relative to groundwater samples and surface water collected upstream of the wastewater facility. ToxCast chemicals were ubiquitous across watershed irrigation sources in abundance, chemical use category, and number. Wastewater-exposed soybeans had the fewest extractable TICs in plant tissues of all irrigation sources. More ToxCast chemicals were identified in CIPS than extracted from irrigation sources by solid phase extraction. ToxCast chemicals in beans and CIPS were similar in number, chemical use category, and log Kow range. CIPS appear to serve as a useful surrogate for ToxCast chemical uptake in beans, the edible food product.

Screening of Contaminants of Emerging Concern in Surface Water and Wastewater Effluents, Assisted by the Persistency-Mobility-Toxicity Criteria

Contaminants of emerging concern (CECs) are compounds of diverse origins that have not been deeply studied in the past which are now accruing growing environmental interest. The NOR-Water project aimed to identify the main CECs and their sources in the water environment of Northern Portugal-Galicia (located in northwest Spain) transnational region. To achieve these goals, a suspect screening analytical methodology based on the use of liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) was applied to 29 sampling sites in two campaigns. These sampling sites included river and sea water, as well as treated wastewater. The screening was driven by a library of over 3500 compounds, which included 604 compounds prioritized from different relevant lists on the basis of the persistency, mobility, and toxicity criteria. Thus, a total of 343 chemicals could be tentatively identified in the analyzed samples. This list of 343 identified chemicals was submitted to the classification workflow used for prioritization and resulted in 153 chemicals tentatively classified as persistent, mobile, and toxic (PMT) and 23 as very persistent and very mobile (vMvP), pinpointing the relevance of these types of chemicals in the aqueous environment. Pharmaceuticals, such as the antidepressant venlafaxine or the antipsychotic sulpiride, and industrial chemicals, especially high production volume chemicals (HPVC) such as ε-caprolactam, were the groups of compounds that were detected at the highest frequencies.

Tracking pollutants in a municipal sewage network impairing the operation of a wastewater treatment plant

This work provides a screening of organic contaminants and characterization of the dissolved organic matter in the sewer network until the municipal wastewater treatment plant (WWTP), identifying the network areas with a higher degree of contamination and their impact on the WWTP performance, particularly in the activated sludge reactor. Three monitoring campaigns were carried out at six selected locations of the sewage system (PVZ-1, PVZ-2, PS-F, PS-VC, CP-VC, and PS-T), influent (WWTP_INF) and effluent (WWTP_EFF) of the WWTP. Advanced analytical techniques were employed, namely excitation/emission matrix fluorescence-parallel factor analysis (EEM-PARAFAC), size exclusion chromatography with organic carbon detector (SEC-OCD), and liquid chromatography with high-resolution-mass spectrometric detection (LC-HRMS). EEM-PARAFAC showed higher fluorescence intensity for the protein-like component (C2), particularly at CP-VC (near seafood industries) associated with the presence of surfactants (~50 mg/L). SEC-OCD highlighted the WWTP efficiency in removing low molecular weight acids and neutrals. LC-HRMS tentatively identified 108 compounds of emerging concern (CEC) and similar detection patterns were obtained for all wastewater samples, except for PVZ-2 (lower detection), many of which occurred in the effluent. Eight CECs included on relevant Watch-Lists were detected in all WWTP_EFF samples. Furthermore, 111 surfactants were detected, the classes more frequently found being alcohol ethoxylates (AEOs), nonylphenol polyethoxylates (NPEOs) and linear alkylbenzene sulphonates (LAS). The continuous presence of LAS and NPEOs allied to surfactants concentrations in the WWTP_INF of 15-20 mg/L, with CP-VC location (linked with food industries) as an important contributor, explain the morphological changes in the activated sludge and high LAS content in the dewatered sludge, which may have impacted WWTP performance.

Functionalized mesoporous silicas SBA-15 for heterogeneous photocatalysis towards CECs removal from secondary urban wastewater

The photocatalytic activity of TiO₂ nanoparticles (NPs) supported on mesoporous silica SBA-15 (TiO₂/SBA-15) was evaluated for the photodegradation of sulfadiazine (SDZ), as target contaminant of emerging concern (CEC), using either pure water solutions (PW) or a real secondary urban wastewater (UWW) spiked with SDZ. For this purpose, TiO₂/SBA-15 samples with 10, 20 and 30% TiO₂ (w/w) were prepared by the sol-gel post synthetic method on pre-formed SBA-15, using titanium (IV) isopropoxide as a precursor. The TiO₂/SBA-15 materials were characterized by HRTEM, SAXS and XRD, nitrogen adsorption isotherms and UV-vis diffuse reflectance spectroscopy. TiO₂ NPs were shown to be attached onto the external surface, decorating the SBA-15 particles. The TiO₂/SBA-15 catalysts were active in SDZ photodegradation using the annular FluHelik photoreactor, when irradiated with UVA light. The 30% TiO₂/SBA-15 sample presented the best performance in optimization tests performed using PW, and it was further used for the tests with UWW. The photocatalytic activity of 30% TiO₂/SBA-15 was higher (56% SDZ degradation) than that of standard TiO₂-P25 (32% SDZ degradation) in the removal of SDZ spiked in the UWW ([SDZ] = 2 mg L^-1). The photodegradation of SDZ with 30% TiO₂/SBA-15 eached 90% for UWW spiked with a lower SDZ concentration ([SDZ] = 40 μg L^-1). Aside of SDZ, a suit of 65 other CECs were also identified in the UWW sample using LC-MS spectrometry. A fast-screening test showed the heterogeneous photocatalytic system was able to remove most of the detected CECs from UWW, by either adsorption and/or photocatalysis.

Development and application of an in-house library and workflow for gas chromatography-electron ionization-accurate-mass/high-resolution mass spectrometry screening of environmental samples

This work presents an optimized gas chromatography–electron ionization–high-resolution mass spectrometry (GC-EI-HRMS) screening method. Different method parameters affecting data processing with the Agilent Unknowns Analysis SureMass deconvolution software were optimized in order to achieve the best compromise between false positives and false negatives. To this end, an accurate-mass library of 26 model compounds was created. Then, five replicates of mussel extracts were spiked with a mixture of these 26 compounds at two concentration levels (10 and 100 ng/g dry weight in mussel, 50 and 500 ng/mL in extract) and injected in the GC-EI-HRMS system. The results of these experiments showed that accurate mass tolerance and pure weight factor (combination of reverse-forward library search) are the most critical factors. The validation of the developed method afforded screening detection limits in the 2.5–5 ng range for passive sampler extracts and 1–2 ng/g for mussel sample extracts, and limits of quantification in the 0.6–3.2 ng and 0.1–1.8 ng/g range, for the same type of samples, respectively, for 17 model analytes. Once the method was optimized, an accurate-mass HRMS library, containing retention indexes, with ca. 355 spectra of derivatized and non-derivatized compounds was generated. This library (freely available at https://doi.org/10.5281/zenodo.5647960), together with a modified Agilent Pesticides Library of over 800 compounds, was applied to the screening of passive samplers, both of polydimethylsiloxane and polar chemical integrative samplers (POCIS), and mussel samples collected in Galicia (NW Spain), where a total of 75 chemicals could be identified.

Risk-based prioritization of suspects detected in riverine water using complementary chromatographic techniques

Surface waters are widely used as drinking water sources and hence their quality needs to be continuously monitored. However, current routine monitoring programs are not comprehensive as they generally cover only a limited number of known pollutants and emerging contaminants. This study presents a risk-based approach combining suspect and non-target screening (NTS) to help extend the coverage of current monitoring schemes. In particular, the coverage of NTS was widened by combining three complementary separations modes: Reverse phase (RP), Hydrophilic interaction liquid chromatography (HILIC) and Mixed-mode chromatography (MMC). Suspect lists used were compiled from databases of relevant substances of very high concern (e.g., SVHCs) and the concentration of detected suspects was evaluated based on ionization efficiency prediction. Results show that suspect candidates can be prioritized based on their potential risk (i.e., hazard and exposure) by combining ionization efficiency-based concentration estimation, in vitro toxicity data or, if not available, structural alerts and QSAR.based toxicity predictions. The acquired information shows that NTS analyses have the potential to complement target analyses, allowing to update and adapt current monitoring programs, ultimately leading to improved monitoring of drinking water sources.

Passive sampling with suspect screening of polar pesticides and multivariate analysis in river catchments: Informing environmental risk assessments and designing future monitoring programmes

Pollution of surface water by polar pesticides is a major environmental risk, particularly in river catchments where potable water supplies are abstracted. In these cases, there is a need to understand pesticide sources, occurrence and fate. Hence, we developed a novel strategy to improve water quality management at the catchment scale using passive sampling coupled to suspect screening and multivariate analysis. Chemcatcher® passive sampling devices were deployed (14 days) over a 12 month period at eight sites (including a water supply works abstraction site) in the Western Rother, a river catchment in South East England. Sample extracts (n = 197) were analysed using high-resolution liquid chromatography-quadrupole-time-of-flight mass spectrometry and compounds identified against a commercially available database. A total of 128 pesticides from different classes were found. Statistical analysis of the qualitative screening data was used to identify clusters of pesticides with similar spatiotemporal pollution patterns. This enabled pesticide sources and fate to be identified. At the water supply works abstraction site, spot sampling and passive sampling were found to be complementary, however, the passive sampling method in conjunction with suspect screening detected 50 pesticides missed by spot sampling combined with targeted analysis. Geospatial data describing pesticide application rates was found to be poorly correlated to their detection frequency using the Chemcatcher®. Our analysis prioritised 61 pesticides for inclusion in a future water quality risk assessment at the abstraction site. It was also possible to design a seasonal monitoring programme to effectively characterise the spatiotemporal pesticide profiles within the catchment. A work flow of how to incorporate passive sampling coupled to suspect screening into existing regulatory monitoring is proposed. Our novel approach will enable water quality managers to target the mitigation (non-engineered actions) of pesticide pollution within the catchment and hence, to better inform drinking water treatment processes and save on operational costs.