Use of Quadrupole Time-of-Flight Mass Spectrometry in Environmental Analysis: Elucidation of Transformation Products of Triazine Herbicides in Water after UV Exposure

The photo- and microbial degradation kinetics and pathways of sulfadoxine in seawater elucidated by liquid chromatography coupled with time-of-flight mass spectrometry

Sulfadoxine (SDX) is a broad-spectrum veterinary antibiotic, which was used alone for the treatment of various infections in the past, and detected ubiquitously in the aqueous environment. However, understanding SDX's photo- and microbial degradation within the environment, especially in marine matrixes, remains limited. This research hones in on SDX's degradation dynamics in seawater. Photodegradation emerges as the dominant process, surpassing microbial degradation in speed and efficiency. Notably, 90% of SDX is photo-degraded within 12 h, while only 52% is removed via microbial degradation over two weeks. Time-of-flight mass spectrometry provides high-resolution molecular mass information on degradation products. The molecular structures of hydrolysis, photo-, and microbial degradation products are deduced from accurate precursor and fragment ion masses, alongside an integrated data processing workflow. Six hydrolysis products arise from the treatment, and photodegradation and microbial degradation yield nine and eighteen products, respectively. Molecular insights from these products inform plausible degradation pathways involving hydrolysis, photodegradation, and microbial degradation. Processes like bond cleavage, methylation, hydroxylation, oxidation, reduction, and methoxylation are identified and associated with degradation. This study presents a comprehensive workflow for acquiring and processing degradation product data linked to emerging organic pollutants. Moreover, it contributes to our comprehension of the environmental fate of veterinary drugs in marine ecosystems.

Impact of seasonality, redox conditions, travel distances and initial concentrations on micropollutant removal during riverbank filtration at four sites

Riverbank filtration (RBF) is a reliable water purification technique that has proven to be suitable for the removal of organic micropollutants. Its removal efficiency and dependency on a variety of factors such as redox conditions, temperatures, geology, travel times, level of initial micropollutant concentrations and seasonality were investigated during three seasonal sampling campaigns. Two anoxic (silty sand, Ems river) and two oxic (gravel, Ruhr river) RBF sites in Germany with different travel distances (42-633 m) were studied. Micropollutant concentrations were examined using a large-volume direct injection liquid chromatography method coupled to high-resolution mass spectrometry. Seasonal differences in micropollutant concentrations in the rivers were observed for chlorotolurone, diclofenac, terbuthylazine, mecoprop-P, MCPA (2-methyl-4-chlorophenoxyacetic acid) and propyphenazone. Redox dependencies in RBF were only found for sulfamethoxazole, propyphenazone, terbuthylazine and carbamazepine. Data for oxazepam, tramadol, N-desmethyl-tramadol, tilidin-desmethyl, carbamazepine and carbendazim indicate a required minimum travel distance of e.g. 100-200 m for the complete removal. Notably, travel time did not seem to be a substantial factor for their removal. High conductivity aquifers are also well suited for micropollutant removal. Seasonal initial concentration level variations showed no impact on the resulting abstraction well concentrations. Although the calculated removal efficiencies varied, they proved to be improper for seasonal raw water quality comparison. Knowledge of micropollutant behavior in riverbank filtration was broadened and RBF proved to be well suited for effective micropollutant reduction throughout the year, yet for a complete removal long travel distances or further technical purification steps are required.

Entry of biocides and their transformation products into groundwater via urban stormwater infiltration systems

Biocides are, inter alia, applied as preservatives on facades to prevent the growth of microorganisms. Their incomplete mineralization results in new compounds, so-called transformation products (TPs). Rain causes that both applied biocides and their TPs leach from facades with stormwater into the urban aquatic environment. This study is the first to investigate the introduction of the biocides Diuron, Terbutryn, and Octylisothiazolinone (OIT) and their TPs into the groundwater via urban stormwater infiltration systems. In this study, the TPs of these biocides were created by laboratory photolysis and elucidated using LC-HRMS. The results were then used to analyze TPs by LC-MS/MS in stormwater and groundwater samples, which were taken from an urban swale-trench system and from groundwater wells upgradient and downgradient of the infiltration system. A sprinkling experiment was conducted to evaluate facades as a contamination source. Biodegradation tests were conducted to determine bio-persistence of biocides and their TPs. Fourteen TPs were identified under laboratory photolysis. TP-186, TP-210, and TP-256 of Terbutryn were hitherto unknown. Nine TPs were qualitatively detected in environmental water samples. Parent compounds, TP-219 of Diuron and TP-212, TP-214, and TP-226 of Terbutryn were detected at a maximum concentration of 140 ng L^-1 during stormwater events. Concentrations in groundwater were considerably below German drinking water limits, but were higher in groundwater samples downgradient from the investigated swale-trench system than in those collected upgradient. Neither the biocides nor most of their TPs were readily biodegradable under simulated surface water conditions. The results show that entry of biocides and their TPs into groundwater is caused by infiltration of urban stormwater.

Mechanistic consideration of the photochemical transformation of domoic acid (algal toxin) in DOM-Rich brackish water

Domoic acid (DA) is a neurotoxin generated by several diatom species in harmful algae blooms (HABs). We report the photo-induced transformation products (TPs) and degradation mechanisms of DA in dissolved organic matter (DOM)-rich freshwater and brackish water. High-resolution quadrupole time-of-flight mass spectrometry (QTOF-MS) and the multivariate statistical strategy orthogonal partial least-squares discriminant analysis (OPLS-DA) identified 36 and 23 potential TPs in DOM-rich freshwater and brackish water, respectively. The main reactive sites of DA are the conjugated double bond and proline ring. Isomerization is the predominant transformation pathway induced by excited-state triplet DOM (³DOM^∗). The second-order rate constant of the isomerization reaction was measured as (3.8 ± 0.2) × 10⁸ M^-1 s^-1. The inverse correlation between the dissolved oxygen (DO) concentration and the rate of photo-induced DA isomerization was revealed. Furthermore, under halide-present conditions, halide radicals are mainly responsible for the differentiation of products by quenching hydroxyl radicals and generating unique organic peroxide products. Our results indicated that halide radicals could be important in the photochemical transformation of organic contaminants in high saline environments.

Photochemical Transformation of Nicotine in Wastewater Effluent

Nicotine is a highly toxic tobacco alkaloid that is ubiquitous in wastewater effluent. For the first time, we report the identification of the products and the pathways for the photodegradation of nicotine in an effluent matrix under simulated solar irradiation. Nicotine was found to be degraded by triplet-state organic matter (³OM*), thus indicating that electron transfer is a preferred reaction mechanism. Using the multivariate statistical strategies orthogonal projection to latent structures discriminant analysis (OPLS-DA) and hierarchical clustering, 49 potential transformation products (TPs) of nicotine were successfully extracted from the water matrix via high-resolution ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). Overall, 30 TPs, including 4 groups of nonseparated isomeric photo TPs, were identified with various levels of confidence based on the tandem mass spectrometry information on standard compounds and the isotope-labeling method (using rac-nicotine-2',3',3'-D₃, rac-nicotine-¹³CD₃, and rac-nicotine-D₄) under air-saturated conditions. The pyrrolidine ring of nicotine was found to be the reactive site under sunlight irradiation. Pseudooxynicotine was the main primary TP from nicotine, with a maximum transformation ratio of 64%. Nicotinic acid, cotinine, 3'-hydroxycotinine, and myosmine were the final stable TPs after 72 h of solar irradiation, with yields of 13%, 3%, 5%, and 5%, respectively.

Transformation products elucidation of forchlorfenuron in postharvest kiwifruit by time-of-flight mass spectrometry

Forchlorfenuron (1-(2-chloro-4-pyridyl)-3-phenylurea, FCF) is a plant growth regulator, being extensively used for increasing kiwifruit size. The toxicological properties of its may persist in their transformation products (TPs) or even higher toxicity than FCF. TPs elucidation of FCF in postharvest kiwifruit (Actinidia chinensis, Chinese gooseberry) by the liquid chromatography ionization hybrid ion trap and time-of-flight mass spectrometry (LC-ESI-IT-TOF/MS) in positive mode was the objective of the present study. Fifteen days after full bloom, kiwifruits were dipped for 5s with high dosage FCF solution (60 mg/L), so that sufficient peaks could be detected. The chemical structure of unknown TPs was analyzed in combination of functions of LCMS-IT-TOF, such as high-accurate MSⁿ, formula predictor, metabolite structural analysis software MetID Solution, profiling solution metabolomics software, and neutral loss, characteristic isotopic patterns of chlorine, the fragmentation pattern and retention time of standard substances, nitrogen rule, chemical components of kiwifruit. Total 17 TPs were detected via comparisons of their accurate MSⁿ data of commercial analytical standards and synthesized standards with high purity, such as 4-amino-2-chloropyridine, phenylurea, 2-hydroxy-FCF, 1-(2-chloro-6-((3, 4, 5-trihydroxy-6-(hydroxymethyl) tetrahydro-2H-pyran-2-yl) oxy) pyridin-4-yl)-3-phenylurea, 1, 3-bis (2-chloropyridin-4-yl) urea, 1,3-diphenylurea, 1-(2-chloropyridin-4-yl)urea, FCF-2-O-β-D-glucoside, and so on. The major transformation pathways of FCF in kiwifruit were biochemical and photochemical cleavage pathway. The experimental results indicate that LCMS-IT-TOF is powerful and effective tool for identification of FCF TPs.

Identification of unknown microcontaminants in Dutch river water by liquid chromatography-high resolution mass spectrometry and nuclear magnetic resonance spectroscopy

In the past decade during automated surface water monitoring in the river Meuse at border station Eijsden in The Netherlands, a set of unknown compounds were repeatedly detected by online liquid chromatography-diode-array detection in a relatively high signal intensity. Because of the unknown nature of the compounds, the consequently unknown fate of this mixture in water treatment processes, the location being close to the water inlet of a drinking water supply company and their possible adverse public health effects, it was deemed necessary to elucidate the identity of the compounds. No data are available for the occurrence of these unknowns at downstream locations. After concentration and fractionation of a sample by preparative Liquid Chromatography, identification experiments were performed using Liquid Chromatography-High Resolution Mass Spectrometry (LC-HR-MS) combined with High Resolution Nuclear Magnetic Resonance Spectroscopy (HR-NMR). Accurate mass determination of the unknown parent compound and its fragments obtained in MS/MS provided relevant information on the elemental composition of the unknown compounds. With the use of NMR techniques and the information about the elemental composition, the identity of the compounds in the different sample fractions was determined. Beside some regularly detected compounds in surface water, like caffeine and bisphenol-S, five dihydroxydiphenylmethane isomers were identified. The major unknown compound was identified as 4,4'-dihydroxy-3,5,3',5'-tetra(hydroxymethyl)diphenylmethane. This compound was confirmed by analysis of the pure reference compound. This is one of the first studies that employs the combination of high resolution MS with NMR for identification of truly unknown compounds in surface waters at the μg/L level. Five of the seven identified compounds are unexpected and not contained in the CAS database, while they can be presumed to be products generated during the production of resins.

Anticipating the fate and impact of organic environmental contaminants: a new approach applied to the pharmaceutical furosemide

The presence of trace levels of organic contaminants in the environment is currently an environmental concern. When these contaminants are subjected to environmental transformations, environmental transformation products (ETPs) are obtained, whose structures often remain unknown. The absence of information concerning these new compounds makes them unavailable and consequently makes their environmental detection as well as their (eco)toxicological study impossible. This report describes a multidisciplinary approach that seeks to both anticipate the fate and evaluate the impact of organic environmental contaminants. Our approach consists of three steps. First, isolated and fully characterized transformation products (TPs) of the parent molecule are obtained. In the second step, the parent molecule is subjected to environmentally relevant transformations to identify plausible ETPs. The detection of previously characterized TPs allows the concomitant identification of plausible ETPs. The third step is devoted to the toxicological evaluation of the identified plausible ETPs. Such an approach has recently been applied to furosemide and has allowed the identification of its main TPs. This report now seeks to identify and evaluate toxicologically plausible ETPs of this drug, which is also known as an environmental contaminant.

Investigation of cannabis biomarkers and transformation products in waters by liquid chromatography coupled to time of flight and triple quadrupole mass spectrometry

11-Nor-9-carboxy-Δ(9)-tetrahydrocannabinol (THC-COOH) is commonly selected as biomarker for the investigation of cannabis consumption through wastewater analysis. The removal efficiency of THC-COOH in wastewater treatment plants (WWTPs) has been reported to vary between 31% and 98%. Accordingly, possible transformation products (TPs) of this metabolite might be formed during treatment processes or in receiving surface water under environmental conditions. In this work, surface water was spiked with THC-COOH and subjected to hydrolysis, chlorination and photo-degradation (both ultraviolet and simulated sunlight) experiments under laboratory-controlled conditions. One hydrolysis, eight chlorination, three ultraviolet photo-degradation and seven sunlight photo-degradation TPs were tentatively identified by liquid chromatography coupled to quadrupole time-of-flight mass spectrometer (LC-QTOF MS). In a subsequent step, THC-COOH and the identified TPs were searched in wastewater samples using LC coupled to tandem mass spectrometry (LC-MS/MS) with triple quadrupole. THC-COOH was found in all influent and effluent wastewater samples analyzed, although at significant lower concentrations in the effluent samples. The removal efficiency of WWTP under study was approximately 86%. Furthermore, THC-COOH was also investigated in several surface waters, and it was detected in 50% of the samples analyzed. Regarding TPs, none were found in influent wastewater, while one hydrolysis and five photo-degradation (simulated sunlight) TPs were detected in effluent and surface waters. The most detected compound, resulting from sunlight photo-degradation, was found in 60% of surface waters analyzed. This fact illustrates the importance of investigating these TPs in the aquatic environment.

Aqueous photodegradation of sethoxydim herbicide: Qtof elucidation of its by-products, mechanism and degradation pathway

The photochemical fate of sethoxydim herbicide in water was studied under simulated sunlight radiation (Suntest apparatus). This compound exhibited a rapid degradation rate in water with a half-life of approximately 1h, which is in accordance with the high calculated value of the quantum yield (Φ=0.26). Consequently, the photolysis of sethoxydim should be considered as an efficient route of sethoxydim removal in aqueous media. During the photodegradation studies, ten by-products were detected, and their identification was accomplished using high-performance liquid chromatography (HPLC) coupled with quadrupole time-of-flight mass spectrometry (Qtof) and electrospray ionization in positive mode (ESI+). A detailed and exhaustive study of the mass spectra of the precursor ions and their MS/MS fragmentation patterns allowed for their identification. The photodegradation products resulted from the cleavage and isomerization of the NO bond of the oxime, oxidation of the sulfur atom, oxidative CS bond cleavage and Beckmann rearrangement followed by intramolecular cyclization. Additionally, the reactive species involved and a plausible mechanism for the photodegradation of sethoxydim in water are discussed. Finally, based on the identified products, a rational pathway for the photodegradation of sethoxydim in water is proposed.

Identification of new omeprazole metabolites in wastewaters and surface waters

Omeprazole is one of the world-wide most consumed pharmaceuticals for treatment of gastric diseases. As opposed to other frequently used pharmaceuticals, omeprazole is scarcely detected in urban wastewaters and environmental waters. This was corroborated in a previous research, where parent omeprazole was not detected while four transformation products (TPs), mainly resulting from hydrolysis, were found in effluent wastewaters and surface waters. However, the low abundance of omeprazole TPs in the water samples together with the fact that omeprazole suffers an extensive metabolism, with a wide range of excretion rates (between 0.01 and 30%), suggests that human urinary metabolites should be investigated in the water environment. In this work, the results obtained in excretion tests after administration of a 40 mg omeprazole dose in three healthy volunteers are reported. Analysis by liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF MS) reported low concentrations of omeprazole in urine. Up to twenty-four omeprazole metabolites (OMs) were detected and tentatively elucidated. The most relevant OM was an omeprazole isomer, which obviously presented the same exact mass (m/z 346.1225), but also shared a major common fragment at m/z 198.0589. Subsequent analyses of surface water and effluent wastewater samples by both LC-QTOF MS and LC-MS/MS with triple quadrupole revealed that this metabolite (named as OM10) was the compound most frequently detected in water samples, followed by OM14a and OM14b. Up to our knowledge, OM10 had not been used before as urinary biomarker of omeprazole in waters. On the contrary, parent omeprazole was never detected in any of the water samples. After this research, it seems clear that monitoring the presence of omeprazole in the aquatic environment should be focused on the OMs suggested in this article instead of the parent compound.

Identification of pesticide transformation products in agricultural soils using liquid chromatography/quadrupole-time-of-flight mass spectrometry

RATIONALE

A study of pesticide transformation products (TPs) was carried out in soils of agricultural areas working under integrated pest management programs (IPMs). Bupirimate and cyromazine were the pesticides detected in soils after an initial pre-screening. The aim of this work was the identification of relevant TPs of these two pesticides.

METHODS

Soil samples were extracted by pressurized liquid extraction (PLE), using a mixture of ethyl acetate/methanol (3:1, v/v), and analyzed by ultra-high-pressure liquid chromatography coupled to hybrid quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF-MS). For confirmation purposes, tandem mass spectrometry (MS(2) ) experiments were carried out using QTOF-MS, obtaining specific fragment structures of the pesticides and their degradates.

RESULTS

Retention times and exact masses of the protonated molecules were used for the identification of the pesticides bupirimate (m/z 317.1642) and cyromazine (m/z 167.1040) and their respective TPs, namely ethirimol (m/z 210.1601) and melamine (m/z 127.0727). A novel strategy using pseudo-MS(3) experiments was developed to confirm the structure of bupirimate TP (ethirimol). This strategy consists of generating the particular TP in the ion source, via collision-induced fragmentation, and then performing MS/MS to the fragment ion formed in-source.

CONCLUSIONS

Ethirimol and melamine were identified as degradation products of bupirimate and cyromazine, respectively. The study was applied to the analysis of 15 agricultural soil samples finding bupirimate and ethirimol in seven samples, cyromazine in one sample and melamine in four samples.

Current use of high-resolution mass spectrometry in the environmental sciences

During the last two decades, mass spectrometry (MS) has been increasingly used in the environmental sciences with the objective of investigating the presence of organic pollutants. MS has been widely coupled with chromatographic techniques, both gas chromatography (GC) and liquid chromatography (LC), because of their complementary nature when facing a broad range of organic pollutants of different polarity and volatility. A clear trend has been observed, from the very popular GC-MS with a single quadrupole mass analyser, to tandem mass spectrometry (MS-MS) and, more recently, high-resolution mass spectrometry (HRMS). For years GC has been coupled to HR magnetic sector instruments, mostly for dioxin analysis, although in the last ten years there has been growing interest in HRMS with time-of-flight (TOF) and Orbitrap mass analyzers, especially in LC-MS analysis. The increasing interest in the use of HRMS in the environmental sciences is because of its suitability for both targeted and untargeted analysis, owing to its sensitivity in full-scan acquisition mode and high mass accuracy. With the same instrument one can perform a variety of tasks: pre- and post-target analysis, retrospective analysis, discovery of metabolite and transformation products, and non-target analysis. All these functions are relevant to the environmental sciences, in which the analyst encounters thousands of different organic contaminants. Thus, wide-scope screening of environmental samples is one of the main applications of HRMS. This paper is a critical review of current use of HRMS in the environmental sciences. Needless to say, it is not the intention of the authors to summarise all contributions of HRMS in this field, as in classic descriptive reviews, but to give an overview of the main characteristics of HRMS, its strong potential in environmental mass spectrometry and the trends observed over the last few years. Most of the literature has been acquired since 2005, coinciding with the growth and popularity of HRMS in this field, with a few exceptions that deserve to be mentioned because of their relevance.

Use of quadrupole time-of-flight mass spectrometry to determine proposed structures of transformation products of the herbicide bromacil after water chlorination

The herbicide bromacil has been extensively used in the Spanish Mediterranean region, and although plant protection products containing bromacil have been withdrawn by the European Union, this compound is still frequently detected in surface and ground water of this area. However, the fast and complete disappearance of this compound has been observed in water intended for human consumption, after it has been subjected to chlorination. There is a concern about the possible degradation products formed, since they might be present in drinking water and might be hazardous. In this work, the sensitive full-spectrum acquisition, high resolution and exact mass capabilities of hybrid quadrupole time-of-flight (QTOF) mass spectrometry have allowed the discovery and proposal of structures of transformation products (TPs) of bromacil in water subjected to chlorination. Different ground water samples spiked at 0.5 µg/mL were subjected to the conventional chlorination procedure applied to drinking waters, sampling 2-mL aliquots at different time intervals (1, 10 and 30 min). The corresponding non-spiked water was used as control sample in each experiment. Afterwards, 50 μL of the water was directly injected into an ultra-high-pressure liquid chromatography (UHPLC)/electrospray ionization (ESI)-(Q)TOF system. The QTOF instrument enabled the simultaneous recording of two acquisition functions at different collision energies (MS(E) approach): the low-energy (LE) function, fixed at 4 eV, and the high-energy (HE) function, with a collision energy ramp from 15 to 40 eV. This approach enables the simultaneous acquisition of both parent (deprotonated and protonated molecules) and fragment ions in a single injection. The low mass errors observed for the deprotonated and protonated molecules (detected in LE function) allowed the assignment of a highly probable molecular formula. Fragment ions and neutral losses were investigated in both LE and HE spectra to elucidate the structures of the TPs found. For those compounds that displayed poor fragmentation, product ion scan (MS/MS) experiments were also performed. On processing the data with specialized software (MetaboLynx), four bromacil TPs were detected and their structures were elucidated. To our knowledge, two of them had not previously been reported.

Recent advances in environmental risk assessment of transformation products

When micropollutants degrade in the environment, they may form persistent and toxic transformation products, which should be accounted for in the environmental risk assessment of the parent compounds. Transformation products have become a topic of interest not only with regard to their formation in the environment, but also during advanced water treatment processes, where disinfection byproducts can form from benign precursors. In addition, environmental risk assessment of human and veterinary pharmaceuticals requires inclusion of human metabolites as most pharmaceuticals are not excreted into wastewater in their original form, but are extensively metabolized. All three areas have developed their independent approaches to assess the risk associated with transformation product formation including hazard identification, exposure assessment, hazard assessment including dose-response characterization, and risk characterization. This review provides an overview and defines a link among those areas, emphasizing commonalities and encouraging a common approach. We distinguish among approaches to assess transformation products of individual pollutants that are undergoing a particular transformation process, e.g., biotransformation or (photo)oxidation, and approaches with the goal of prioritizing transformation products in terms of their contribution to environmental risk. We classify existing approaches for transformation product assessment in degradation studies as exposure- or effect-driven. In the exposure-driven approach, transformation products are identified and quantified by chemical analysis followed by effect assessment. In the effect-driven approach, a reaction mixture undergoes toxicity testing. If the decrease in toxicity parallels the decrease of parent compound concentration, the transformation products are considered to be irrelevant, and only when toxicity increases or the decrease is not proportional to the parent compound concentration are the TPs identified. For prioritization of transformation products in terms of their contribution to overall environmental risk, we integrate existing research into a coherent model-based, risk-driven framework. In the proposed framework, read-across from data of the parent compound to the transformation products is emphasized, but limitations to this approach are also discussed. Most prominently, we demonstrate how effect data for parent compounds can be used in combination with analysis of toxicophore structures and bioconcentration potential to facilitate transformation product effect assessment.

Building an empirical mass spectra library for screening of organic pollutants by ultra-high-pressure liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry

Hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) has gained wide acceptance in many fields of chemistry, for example, proteomics, metabolomics and small molecule analysis. This has been due to the numerous technological advances made to this mass analyser in recent years. In the environmental field, the instrument has proven to be one of the most powerful approaches for the screening of organic pollutants in different matrices due to its high sensitivity in full acquisition mode and mass accuracy measurements. In the work presented here, the optimum experimental conditions for the creation of an empirical TOF MS spectra library have been evaluated. For this model we have used a QTOF Premier mass spectrometer and investigated its functionalities to obtain the best MS data, mainly in terms of mass accuracy, dynamic range and sensitivity. Different parameters that can affect mass accuracy, such as lock mass, ion abundance, spectral resolution, instrument calibration or matrix effect, have also been carefully evaluated using test compounds (mainly pesticides and antibiotics). The role of ultra-high-pressure liquid chromatography (UHPLC), especially when dealing with complex matrices, has also been tested. In addition to the mass accuracy measurements, this analyser allows the simultaneous acquisition of low and high collision energy spectra. This acquisition mode greatly enhances the reliable identification of detected compounds due to the useful (de)protonated molecule and fragment ion accurate mass information obtained when working in this mode. An in-house empirical spectral library was built for approximately 230 organic pollutants making use of QTOF MS in MS(E) mode. All the information reported in this paper is made available to the readers to facilitate screening and identification of relevant organic pollutants by QTOF MS.

Dihydrobenzoic acid modified nanoparticle as a MALDI-TOF MS matrix for soft ionization and structure determination of small molecules with diverse structures

Efficient structural characterization is important for quality control when developing novel materials. In this study, we demonstrated the soft ionization capability of the hybrid of immobilized silica and 2,5-dihydrobenzoic acid (DHB) on iron oxide magnetic nanoparticles in MALDI-TOF MS with a clean background. The ratio between SiO(2) and DHB was examined and was found to affect the surface immobilization of DHB on the nanoparticle, critically controlling the ionization efficiency and interference background. Compared with commercial DHB, the functionalized nanoparticle-assisted MALDI-TOF MS provided superior soft ionization with production of strong molecular ions within 5 ppm mass accuracy on a variety of new types of synthetic materials used for solar cells, light emitting devices, dendrimers, and glycolipids, including analytes with either thermally labile structures or poor protonation tendencies. In addition, the enhancements of the molecular ion signal also provided high-quality product-ion spectra allowing structural characterization and unambiguous small molecule identification. Using this technique, the structural differences among the isomers were distinguished through their characteristic fragment ions and comprehensive fragmentation patterns. With the advantages of long-term stability and simple sample preparation by deposition on a regular sample plate, the use of DHB-functionalized nanoparticles combined with high-resolution MALDI-TOF MS provides a generic platform for rapid and unambiguous structure determination of small molecules.

Indirect photodegradation of clethodim in aqueous media. byproduct identification by quadrupole time-of-flight mass spectrometry

Aqueous photolysis of clethodim herbicide in the presence of natural substances such as humic acids (HA), nitrate, and Fe(III) ions has been investigated. The photodegradation rate of clethodim was retarded in the presence of HA compared to ultrapure water, while nitrate ions had no effect. On the other hand, water containing different concentrations of Fe(III) ions enhanced degradation of this herbicide. Clethodim transformation gave rise to the formation of nine byproducts, some of them, to the best of our knowledge, described for the first time in this work. The identification of these photoproducts has been accomplished by coupling liquid chromatography to quadrupole time-of-flight mass spectrometry. The main transformation reactions observed for clethodim were photoisomerization to the Z-isomer, S-oxidation of E- and Z-clethodim isomers giving rise to sulfoxide diastereoisomers, reduction of the oxime moiety to yield clethodim imine, oxidative cleavage of the C-S bond, and S-oxidation of clethodim imine leading to the formation of imine ketone and imine sulfoxide.

Identification of transformation products of organic contaminants in natural waters by computer-aided prediction and high-resolution mass spectrometry

Transformation products (TPs) of organic contaminants in aquatic environments are still rarely considered in water quality and chemical risk assessment, although they have been found in concentrations that are of concern. Since many different TPs can potentially be formed in the environment and analytical standards are typically lacking for these compounds, knowledge on the prevalence of TPs in aquatic environments is fragmentary. In this study, an efficient procedure was therefore developed to comprehensively screen for large numbers of potential TPs in environmental samples. It is based on a target list of plausible TPs that has been assembled using the University of Minnesota Pathway Prediction System (UM-PPS) for the computer-aided prediction of products of microbial metabolism and an extensive search for TPs reported in the scientific literature. The analytical procedure for screening of the compounds on the target list has been developed to allow for the detection of a broad range of compounds in complex environmental samples in the absence of commercially available reference standards. It includes solid phase extraction with broad enrichment efficiency, followed by liquid chromatography and tandem mass spectrometry with high mass resolution and accuracy. The identification of target TPs consisted of extracting the exact mass from the chromatogram, selecting peaks of sufficient intensity, checking the plausibility of the retention time, and interpreting mass spectra. The procedure was used to screen for TPs of 52 pesticides, biocides, and pharmaceuticals in seven representative surface water samples from different regions in Switzerland. Altogether, 19 TPs were identified, including both some well-known and commonly detected TPs, and some rarely reported ones (e.g., biotransformation products of the pharmaceuticals venlafaxine and verapamil, or of the pesticide azoxystrobin). Overall, the rather low number of TPs detected suggests that TPs may not pose a problem of unexpected magnitude for aquatic resources.

Combined use of GC-TOF MS and UHPLC-(Q)TOF MS to investigate the presence of nontarget pollutants and their metabolites in a case of honeybee poisoning

The combined use of gas chromatography (GC) and ultrahigh-pressure liquid chromatography (UHPLC), both coupled to time-of-flight mass spectrometry (TOF MS), has been explored in this work for the investigation of several cases of honeybee poisoning. The procedure applied involves a previous extraction with acetone followed by liquid-liquid extraction with dichloromethane. Both techniques, GC-TOF MS and UHPLC-(Q)TOF MS, have been applied to discover the presence of compounds that might be responsible of honeybee deaths. The application of a nontarget methodological approach to a first case of poisoning allowed the detection of the insecticide coumaphos at high concentration levels in the samples. The presence of possible metabolites of this organophosphorus insecticide was investigated by using both techniques. UHPLC-(Q)TOF MS showed its higher applicability in this case, as most of the metabolites were more polar than the parent compound. Four metabolites were identified by UHPLC-(Q)TOF MS, whereas only two of them were found by GC-TOF MS. The developed methodology was applied to other subsequent poisoning cases in which insecticides such as coumaphos, thiamethoxam, pyriproxyfen, and chlorfenvinphos were identified by both techniques, whereas GC-TOF MS also allowed the detection of fenitrothion and methiocarb. In all positive cases, the confirmation of the presence of the compound detected was feasible by means of accurate mass measurements of up to five ions together with their ion ratio evaluation.

Degradation of reactive dyes in wastewater from the textile industry by ozone: analysis of the products by accurate masses

The present work describes the use of ozone to degrade selected reactive dyes from the textile industry and the analysis of the resulting complex mixture by liquid chromatography/mass spectrometry (LC-MS). To allow certain identification of the substances detected in the wastewater, the original dyes were also investigated either separately or in a synthetic mixture of three dyes (trichromie). Since the reactive dyes are hydrolyzed during the dyeing process, procedures for the hydrolysis were worked out first for the individual dyes. The ozonated solutions were concentrated by solid-phase extraction, which separated very polar or ionic substances from moderately polar degradation products. The latter, which are the primary degradation products, were investigated by liquid chromatography/mass spectrometry with a tandem quadrupole time-of-flight mass analyzer. Accurate masses, which in most cases could be determined with a deviation of <or=5 ppm from the exact value, were also measured. In addition, a diode-array detector was placed before the mass analyzer to provide UV-vis spectra of the products in the same run. With retention times, mass spectra, accurate masses, UV-vis spectra and, of course, knowledge of the structures of the original dyes, plausible structures could be proposed for most of the components of the moderately polar fraction. These structures were confirmed by 1H NMR in cases where it was practical to isolate the degradation products by preparative HPLC.

Investigating the presence of pesticide transformation products in water by using liquid chromatography-mass spectrometry with different mass analyzers

Many pesticide transformation products (TPs) can reach environmental waters as a consequence of their normally having a higher polarity than their parent pesticides. This makes the development of analytical methodology for reliable identification and subsequent quantification at the sub-microgram per liter levels necessary, as required under current legislation. In this paper we report the photodegradation of several pesticides frequently detected in environmental waters from the Spanish Mediterranean region using the high-resolution and exact-mass capabilities of hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) hyphenated to liquid chromatography (LC). Once the main photodegradation/hydrolysis products formed in aqueous media were identified, analytical methodology for their simultaneous quantification and reliable identification in real water samples was developed using on-line solid-phase extraction (SPE)-LC-tandem MS with a triple-quadrupole (QqQ) analyzer. The methodology was validated in both ground and surface water samples spiked at the limit of quantification (LOQ) and 10 x LOQ levels, i.e. 50 and 500 ng/l, obtaining satisfactory recoveries and precision for all compounds. Subsequent analysis of ground and surface water samples resulted in the detection of a number of TPs higher than parent pesticides. Additionally, several soil-interstitial water samples collected from the unsaturated zone were analyzed to explore the degradation/transformation of some pesticides in the field using experimental plots equipped with lisimeters. Several TPs were found in these samples, with most of them having also been detected in ground and surface water from the same area. This paper illustrates the extraordinary potential of LC-MS(/MS) with QTOF and QqQ analyzers for qualitative/structural and quantitative analysis, respectively, offering analytical chemists one of the most powerful tools available at present to investigate the presence of pesticide TPs in water.

Liquid Chromatography Quadrupole Time-of-Flight Mass Spectrometry Analysis of Carbosulfan, Carbofuran, 3-Hydroxycarbofuran, and Other Metabolites in Food

The potential of liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS) to identify and confirm carbosulfan and seven of its main metabolites (carbofuran, 3-hydroxycarbofuran, 3-ketocarbofuran, 3-hydroxy-7-phenol carbofuran, 3-keto-7-phenolcarbofuran, 7-phenolcarbofuran, dibutylamine) at trace levels from food is explored for the first time. The analytical method developed consists of pressurized liquid extraction (PLE) and LC-QqTOF-MS in positive ion mode, which attains unequivocal identification and quantification of the studied compounds in food, at levels well below of those of concern (0.05 mg/kg for the sum of carbosulfan, carbofuran, and 3-hydroxycarbofuran). PLE recoveries ranged from 55 to 94% with limits of quantification from 10 (for carbosulfan, carbofuran, 3-hydroxycarbofuran, and dibutylamine) to 70 microg/kg (3-keto-7-phenolcarbofuran). The method is precise, with relative standard deviations varying between 5 and 11% for the repeatability (within-day) and 8-13% for the reproducibility (interday). This method was used to monitor the presence and fate of the target compounds in orange, potato, and rice crops treated with a commercial product containing carbosulfan. Field degradation studies show that carbofuran, 3-hydroxycarbofuran, and dibutylamine are the main degradation products formed in the environmental disappearance of carbosulfan.

Molecular Imprinting under Molecular Crowding Conditions: An Aid to the Synthesis of a High-Capacity Polymeric Sorbent for Triazine Herbicides

Molecular crowding, an important feature of the molecular environments in biological cells, was applied to the synthesis of antibody-mimic polymers selective for a group of biologically active compounds, the triazine herbicides. Synthesis of these polymers was conducted using molecular imprinting under molecular crowding conditions, whereby atrazine (a template molecule) was complexed with methacrylic acid (a functional monomer) in the presence of a macromolecular crowding agent (either poly(methyl methacrylate) (PMMA) or polystyrene (PS)) followed by cross-linking with ethylene glycol dimethacrylate. After removal of atrazine from the polymer matrix, the retention properties and selectivity of the resultant polymers were assessed by chromatographic tests. The addition of a crowding-inducing agent resulted in polymers with superior retention properties and excellent selectivity for triazine herbicides, as compared to polymers prepared without addition of a crowding-inducing agent. An imprinted polymer prepared in the presence of PS as a crowding agent exhibited a retention factor for atrazine an order of magnitude larger than that of an imprinted polymer prepared in the absence of a crowding agent. NMR results suggest that the crowding agent is capable of promoting hydrogen bond formation between atrazine and methacrylic acid, which could account for the effect of crowding on molecular imprinting.

Fragmentation and gas phase aggregation processes in the laser desorption ionization of chlorodiaminotriazines

Fragmentation and supramolecular aggregation induced during the laser desorption/ionization (LDI) of four chlorodiaminotriazines (simazine, atrazine, terbutylazine and propazine) have been investigated. The laser wavelength employed (266 nm) lies within the first absorption band of the four triazines. The main fragmentation channel observed involves the prompt cleavage of the Cl atom, followed by partial or total fragmentation of the side alkyl chains. Breakage of the triazinic ring becomes efficient at moderate laser powers; however, the deamination of the triazine is not observed to take place. In addition, the formation of both covalent and non-covalent triazinic aggregates in the desorption plume is found to be particularly efficient. Aggregates as large as heptamers are neatly detected, with the observation that those with the most intense signal involve the dechlorinated triazinic fragment. Both aggregation and fragmentation are largely suppressed upon dilution of the triazine under matrix-assisted laser desorption/ionization conditions.

Fast determination of herbicides in waters by ultra-performance liquid chromatography/tandem mass spectrometry

A rapid multiresidue method for the analysis of more than 40 herbicides (such as simazine, terbuthylazine and diuron) in waters has been developed and validated by ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC/MS/MS). Prior to chromatographic determination, the samples were extracted using a solid-phase extraction procedure. The analysis was performed on an Acquity UPLC BEH C(18) column using a gradient elution profile and a mobile phase consisting of methanol and an aqueous solution of formic acid (0.01%). Other chromatographic and MS/MS parameters were optimised in order to improve selectivity and sensitivity of the analytes. The analytes were detected using electrospray ionisation (ESI)-MS/MS in positive ion mode with multiple reaction monitoring (MRM), optimising parameters such as voltage cone, capillary voltage, source and desolvation temperature, and desolvation and cone gas flow. The optimised method provides a rapid separation (less than 10 min) of the selected herbicides in the assayed matrices, and it was validated by the analysis of spiked blank matrix samples. Good linearity was obtained and the repeatability of the method was less than 20% for the lowest calibration point. The limits of detection ranged from 0.002 to 0.02 microg/L, and the limits of quantification from 0.005 to 0.05 microg/L, which were below the values specified by the European Union. Finally, the method was successfully applied to real environmental samples from Andalusia (southern Spain). Terbuthylazine, simazine, atrazine desisopropyl and desethyl terbuthylazine were the herbicides most frequently found in water samples.

Screening and confirmation of 100 pesticides in food samples by liquid chromatography/tandem mass spectrometry

An analytical method for screening, quantitation and confirmation of a group of 100 pesticides in vegetable and fruit samples was developed using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The pesticides studied belonged to different chemical families of herbicides, insecticides and fungicides; some degradation products were included as well. A thorough optimization was performed for each analyte to achieve individual optimum fragmentor and collision energy voltages. Two transitions per parent compound were monitored in a single chromatographic run containing two time segments. A small particle size C(18) column (1.8 microm) was used for the chromatographic separation of the mixture, providing very narrow peaks and allowing an excellent separation of all the analytes in a 30-min period for maximum peak capacity. The method was validated with blank matrices of green pepper, tomato and orange spiked from 0.1 to 100 microg/kg with the pesticide mix. Quantitation was carried out using matrix-matched standard calibration and linearity of response over 3 orders of magnitude was demonstrated (r > 0.99). Limits of detection based on two transitions and ion-ratio requirements ranged between 0.3 and 50 microg/kg. In general, the sensitivity obtained meets the maximum residue levels (MRLs) established by the European Union regulation for food monitoring programs. The analytical performance of the method was evaluated for different types of vegetables and fruits, showing little or no matrix effects, and examples of screening and confirmation of pesticides in these samples are shown here.

Analyses of macrolide antibiotic residues in eggs, raw milk, and honey using both ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry and high-performance liquid chromatography/tandem mass spectrometry

Two liquid chromatography mass spectrometric techniques, i.e. ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/Q-Tof MS) and high-performance liquid chromatography/tandem mass spectrometry (LC/MS/MS), were used for quantification, confirmation or identification of six macrolide antibiotic residues and/or their degradation products in eggs, raw milk, and/or honey. Macrolides were extracted from food samples by acetonitrile or phosphate buffer (0.1 M, pH 8.0), and sample extracts were further cleaned up using solid-phase extraction cartridges. UPLC/Q-Tof data were acquired in Tof MS full scan mode that allowed both quantification and confirmation of macrolides, and identification of their degradation products. LC/MS/MS data acquisition was achieved using multiple reaction monitoring (MRM), i.e. two transitions, to provide a high degree of sensitivity and repeatability. Matrix-matched standard calibration curves with the use of roxithromycin as an internal standard were utilized to achieve the best accuracy of the method. Both techniques demonstrated good quantitative performance in terms of accuracy and repeatability. LC/MS/MS had advantages over UPLC/Q-Tof MS in that its limits of detection were lower and repeatability was somewhat better. UPLC/Q-Tof provided ultimate and unequivocal confirmation of positive findings, and allowed degradation product identification based on accurate mass. The combination of the two techniques can be very beneficial or complementary in routine analysis of macrolide antibiotic residues and their degradation products in food matrices to ensure the safety of food supply.

Analysis of pesticides in water by liquid chromatography-tandem mass spectrometric techniques

Pesticide residues continue to be the focus of many environmental studies, and the number of articles describing the development of more advanced, multiresidue analytical methodologies does not decline. The use of liquid chromatography-mass spectrometry based on single quadrupole or ion trap analyzers is consolidated for this purpose. The implementation, in the near future, of more sophisticated mass analyzers, such as triple quadrupole and hybrid quadrupole-time-of-flight is anticipated for routine analysis. This article reviews the various works published so far in the literature for the determination of pesticides and transformation products (TPs) in water by means of liquid chromatography (LC) coupled to tandem mass spectrometry. It discusses the various ionization sources and analyzers used for this purpose, as well as the extraction procedures employed for previous sample preconcentration. Because of the widespread use of triple quadrupole analyzers for the generation of pesticides levels in water using tandem mass spectrometry, a table compiling the transitions monitored for ca. 70 compounds is also included.

Time of flight mass spectrometry applied to the liquid chromatographic analysis of pesticides in water and food

Liquid chromatography coupled to mass spectrometry (LC-MS) is an excellent technique to determine trace levels of polar and thermolabile pesticides and their degradation products in complex matrices. LC-MS can be equipped with several mass analyzers, each of which provides unique features capable to identify, quantify, and resolve ambiguities by selecting appropriate ionization and acquisition parameters. We discuss in this review the use of LC coupled to (quadrupole) time-of-flight mass spectrometry (LC-(Q)ToF-MS) to determine the presence of target and non-target pesticides in water and food. This technique is characterized by operating at a resolving power of 10,000 or more. Therefore, it gives accurate masses for both parent and fragment ions and enables the measurement of the elemental formula of a compound achieving compound identification. In addition, the combination of quadrupole-ToF permits tandem mass spectrometry, provides more structural information, and enhances selectivity. The purpose of this article is to provide an overview on the state of art and applicability of liquid chromatography time-of-flight mass spectrometry (LC-ToF-MS), and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) for the analysis of pesticides in environmental matrices and food. The performance of such techniques is depicted in terms of accurate mass measurement, fragmentation, and selectivity. The final section is devoted to describing the applicability of LC-(Q)ToF-MS to routine analysis of pesticides in food matrices, indicating those operational conditions and criteria used to screen, quantify, and identify target and "suspected" pesticides and their degradation products in water, fruits, and vegetables. The potential and future trends as well as limitations of LC-(Q)ToF-MS for pesticide monitoring are highlighted.

Application of liquid chromatography/quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS) in the environmental analysis

This paper gives an overview of the potentials of liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QqTOF) in the environmental analysis. Examples of applications of QqTOF instruments for target analysis of pharmaceuticals and pesticides are presented and discussed, as well as applications aimed on the identification of unknown compounds present in environmental waters or on the elucidation of structures of biodegradation and photodegradation products. Specific issues such as uncertainty of mass measurement and quantitative performances are discussed in details.

Multi-residue analysis of pharmaceuticals in wastewater by ultra-performance liquid chromatography–quadrupole–time-of-flight mass spectrometry

In this work, a new multi-residue method using ultra-performance liquid chromatography (UPLC) quadrupole-time-of-flight mass spectrometry (Q-TOF-MS) was developed for screening and confirmation of 29 pharmaceutical compounds belonging to different therapeutical classes: analgesics and antiinflammatories, lipid regulating agents cholesterol lowering statin agents, psychiatric drugs, anti ulcer agents, histamine H2 receptor antagonist, antibiotics and beta-blockers. UPLC uses columns packed with 1.7 microm particles and enables elution of sample components in much narrower, more concentrated bands, resulting in better chromatographic resolution and increased peak height. The typical peak width was 5-10s at base, permitting very good separation of all compounds in 10 min, which represented an approximate three-fold reduction in the analysis time in comparison to conventional high-performance liquid chromatography (HPLC). Unequivocal identification of target pharmaceutical compounds was based on accurate mass measurement of the molecular ions in the TOF mode and by performing collision induced dissociation (CID) in the Q-TOF mode in order to generate accurate mass measurement of the product ions. Using lock mass correction the accurate masses calculated for the product ions deviated from the theoretical masses by 0.2 to 1.3 mDa (root mean square (RMS) value=0.67) and 0.7-6.4 ppm (RMS=3.53), respectively. Quantitation was carried out working in the TOF mode using the narrow window extracted ion chromatograms (nwXICs) of each compound (extracted using a 20 mDa window) yielding relative standard deviation (RSD) from 0.5 to 5.3% (run-to-run) and from 2.1 to 9.1% (day-to-day) and instrumental detection limits (IDLs) from 1 to 200 pg. Analysis of wastewater treatment plant (WWTP) samples gave method detection limits (MDLs) ranging from 10 to 500 ng/L. The UPLC-Q-TOF method was successfully applied to analyze pharmaceutical residues in WWTP samples.

Potential of liquid chromatography/time-of-flight mass spectrometry for the determination of pesticides and transformation products in water

Until now, time-of-flight (TOF) mass analysers have only been very rarely used in pesticide residue analysis (PRA) of water samples. However, the inherent characteristics of TOF MS make these analysers well-suited to this field, mainly for qualitative purposes. Thus, the high sensitivity obtained from full-scan acquisition in comparison to other MS analysers and the high resolution of TOF MS suggest its suitability for screening purposes; it also increases the multiresidue capabilities of methods based on it and decreases the chance of recording false positives. Although these characteristics can also be helpful for quantification, confirmation and elucidation, some limitations on the use of TOF for these purposes have been observed. These limitations are more noticeable when dealing with samples containing very low analyte concentrations, which is the normal situation for PRA in water. The use of hybrid quadrupole-time-of-flight instruments (QTOF) minimises the limitations of TOF, facilitating the simultaneous detection and unequivocal confirmation of pesticides found in the sample. Additionally, the acquisition of accurate product ion full-scan mass spectra can help to elucidate the structures of unknown compounds. In this paper, the potential of TOF and QTOF hyphenated to liquid chromatography for PRA in water is explored, emphasizing both the advantages and limitations of this approach for screening, quantification, confirmation and elucidation purposes. Emphasis is placed on the determination of polar pesticides and transformation products-the analytes that fit well with LC-API-(Q)TOF MS technology.

Use of liquid chromatography quadrupole time-of-flight mass spectrometry in the elucidation of transformation products and metabolites of pesticides. Diazinon as a case study

Liquid chromatography (LC) coupled to hybrid quadrupole time-of-flight (QTOF) mass spectrometry (MS) is a useful analytical tool in the elucidation and confirmation of transformation products (TPs)/metabolites of pesticides with a wide range of polarity, in both environmental and biological samples. Firstly, the versatility of LC allows the determination of very distinct TPs/metabolites as chromatographic conditions can be easily changed and optimized depending on the analytical problem. Secondly, the mass accuracy provided by the TOF analyser allows the assignment of a highly probable empirical formula for each compound and the differentiation between nominal isobaric compounds. Finally, the possibility of performing MS/MS spectra with accurate mass measurements can been used for the final characterization of the TPs/metabolites detected and for the differentiation of isomeric compounds. In this study, the insecticide diazinon was used as model compound, and its photodegradation and metabolism have been investigated by LC-QTOF-MS. On one hand, environmental spiked water was irradiated with a mercury lamp for 9 days, sampling 3-mL aliquots approximately every 12 h. On the other hand, both in vitro and in vivo metabolism experiments were carried out with different substrate concentrations and incubation times. After centrifugation, and protein precipitation in the in vitro and in vivo studies, 50-microL aliquots of both environmental and biological samples were directly injected into the LC electrospray ionization QTOF system. The most important transformation processes were found to be hydrolysis of the ester moiety, hydroxylation in the aromatic ring or in one of the alkylic groups, oxidation of the sulfur atom on the P=S cleavage or a combination of these processes, with the highest number of compounds being found in the photodegradation study. Very polar compounds, such as diethyl phosphate and diethyl thiophosphate, were detected after direct injection of the aqueous sample, which was feasible owing to the characteristics of the LC. In MS mode, mass errors were below 3 mDa, leading to an empirical formula for each compound. MS/MS spectra with accurate mass were used for the final elucidation of the compounds detected.