Chemical tracers for Wildfires-Analysis of runoff surface Water by LC/Q-TOF-MS.

A quantitative methodology using high resolution mass spectrometry was developed for the identification of organic compounds derived from wildfires in surface water samples. The methodology involves the use of solid-phase extraction (SPE) followed by detection using liquid chromatography-quadrupole time of flight-mass spectrometry (LC/Q-TOF-MS) for a group of fourteen chemical compounds (pyridine, benzene, naphthalene and biphenyl polycarboxylic acids). All compounds were successfully separated chromatographically using a reversed phase column and they were identified by accurate mass using the deprotonated species and their main fragment ions. The method produced excellent accuracies (>95%) and precisions (3-10%) for all the compounds studied. This methodology was successfully applied to the identification of fourteen compounds in runoff surface waters impacted by wildfires in Colorado in 2020. Concentrations of individual compounds ranging from 0.1 to 59.5 µg/L were found in wildfire impacted waters, with totals of ∼200 µg/L, thus showing these compounds as chemical tracers of wildfire events at significantly high concentrations. In addition, non-target analysis using chromatography patterns and mass spectrometry identification by MS-MS revealed other polycarboxylic acid isomers were also present in runoff surface water samples.

Wildfires: Identification of a new suite of aromatic polycarboxylic acids in ash and surface water.

Ash and surface water samples collected after wildfires in four different geographical locations (California, Colorado, Kansas and Alberta) were analyzed. The ash samples were leached with deionized water, and leachates were concentrated by solid phase extraction and analyzed by liquid chromatography/time-of-flight mass spectrometry. In addition, three surface water samples and a lysimeter water sample were collected from watersheds recently affected by fire in California and Colorado, and analyzed in similar fashion. A suite of benzene polycarboxylic acids (BPCAs), with two and three carboxyl groups and their corresponding isomers were identified for the first time in both ash leachates and water samples. Also found was a pyridine carboxylic acid (PCA), 3,5-pyridine dicarboxylic acid. Furthermore, putative identifications were made for other carboxylated aromatic acids: quinolinic, naphthalenic, and benzofuranoic acid carboxylates. The wildfire ashes, a controlled wood ash, and post-fire surface water samples suggest that burned woody material, along with surface plant-material and heated o-horizon soil organic matter, contribute to both BPCAs and PCAs in runoff. This study is the first of its kind to identify this suite of aromatic acids in wildfire ash and surface water samples. These data make an important contribution to the nature of dissolved organic matter from wildfire and are useful to better understand the impact of wildfire on water quality and drinking water sources.

Sustainable microalgae-based technology for biotransformation of benzalkonium chloride in oil and gas produced water: A laboratory-scale study.

Many countries have implemented stringent regulatory standards for discharging produced water (PW) from the oil and gas extraction process. Among the different chemical pollutants occurring in PW, surfactants are widely applied in the oil and gas industry to provide a barrier from metal corrosion. However, the release of these substances from the shale formation can pose serious hazardous impacts on the aquatic environment. In this study, a low-cost and eco-friendly microalgae laboratory-scale technology has been tested for biotransformation of benzalkonium chloride (BACC12 and BACC14) in seawater and PW during 14-days of treatment (spiked at 5 mg/L). From the eight microalgae strains selected, Tetraselmis suecica showed the highest removal rates of about 100% and 54% in seawater and PW, respectively. Suspect screening analysis using liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) allowed the identification of 12 isomeric intermediates generated coming from biotransformation mechanisms. Among them, the intermediate [OH-BACC12] was found as the most intense compound generated from BACC12, while the intermediate [2OH-BACC14] was found as the most intense compound generated from BACC14. The suggested chemical structures demonstrated a high reduction on their amphiphilic properties, and thus, their tendency to be adsorbed into sediments after water discharge. In this study, Tetraselmis suecica was classified as the most successful specie to reduce the surfactant activity of benzalkonium chloride in treated effluents.

Determination of dextromethorphan and dextrorphan solar photo-transformation products by LC/Q-TOF-MS: Laboratory scale experiments and real water samples analysis.

This work discusses the identification of the transformation products (TPs) generated during the photolytic degradation of dextromethorphan (DXM) and its metabolite dextrorphan (DXO), under simulated solar radiation in aqueous solutions (Milli-Q water and river water) in order to determinate its behavior into the aquatic environment. Tentative identification of the TPs was performed by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS), following a suspect screening approach. The use of high resolution-mass spectrometry (HRMS) allowed the tentative identification of DXM and DXO photoproducts based on the structure proposed by an in silico software, the accurate mass measurement, the MS/MS fragmentation pattern and the molecular formula finding. A total of 19 TPs were found to match some of the accurate masses included in a suspect list, and they were all tentatively identified by their characteristic MS-MS fragments. Most of the TPs identified showed a minor modified molecular structure like the introduction of hydroxyl groups, or demethylation. The time-evolution of precursors and TPs were monitored throughout the experiments, and degradation kinetics were presented for each analyte. Finally, the occurrence of DXM, DXO, and their tentatively proposed photodegradation TPs was evaluated in both surface and wastewater. In all real matrices, the results showed that the highest concentration was detected for DXO, followed by TP-244 (N-desmethyldextrorphan) and DXM.

Desalting and Concentration of Common Hydraulic Fracturing Fluid Additives and their Metabolites with Solid-Phase Extraction.

This work describes the development of a solid-phase extraction method capable of detecting common fracturing fluid additives in flowback and produced water with mass spectrometry. Dissolved organic carbon (DOC) was used as a bulk measurement to investigate the retentive capacity of seven sorbents and to determine a loading volume. Conductivity was used to determine rinse volume. Based on this, four sorbents (HLB, PPL, Carbon, and C-18) were selected for further investigation of their ability to recover common fluid additives. Enrichment factors were calculated for poly(ethylene) glycols (PEGs), PEG-amines, and their metabolites PEG-carboxylates and PEG-carboxylate-amines, poly(propylene) glycols (PPGs), and linear alkyl ethoxylates (LAEs). The sorbent HLB gave the greatest enrichment for all of these compounds, with an average of 8.0× for PEGs, 11.9× for PEG-amines, 4.9× for PEG-carboxylates, and 21.6× for LAEs, though enrichment was highly dependent on sample composition. The effect was more pronounced for higher molecular weight compounds and enabled detection of some compounds in saltier samples. Then, HLB was used to recover these additives from 1:200 and 1:1000 dilutions in groundwater, illustrating the ability of solid-phase extraction to detect these compounds at low levels (<100 ppb) and highlighting the utility of desalting. This method was used to identify ethoxylated amines in flowback and produced waters from across the country.

Nontargeted Screening of Water Samples Using Data-Dependent Acquisition with Similar Partition Searching.

A rapid screening method for the detection of nontargeted compounds in surface water samples was developed using MS-MS high-resolution mass spectrometry and data-dependent acquisition. The key parameters for the acquisition method were optimized using five model compounds with diverse chemical characteristics. The parameter selection required optimization between the total number of precursor ions that could be selected in an LC-MS run, the quality of each MS (full range) spectrum, and the quality of each MS-MS fragmentation spectrum. After the acquisition method was optimized, 18 surface water samples from rivers, reservoirs, and effluents from wastewater treatment plants were analyzed, generating 41625 MS-MS spectra in about 14 h. The raw data were then converted into two generic formats using the open-access program MSConvert. A combinatorial approach, similar partition searching (SPS), was then used to putatively identify analytes from the accurate mass of each analyte (adjusted for the adduct mass) and the corresponding MS-MS spectra were obtained. In this approach, the structures of about 250000 common compounds, stored in a large database as mathematical partitions of their exact mass, were compared directly to each MS-MS spectrum. Compounds with a similar mass and retention time were grouped together and labeled as "Analytes", using an Excel Add-In. The isotope ratio data from the MS spectrum, the corresponding MS-MS spectra, and the putative identifications were then imported into an Access relational database to facilitate sorting, searching, filtering, and querying the results. This allowed final inspection to assess confidence of the identifications made through the nontargeted screening.

Molecular Identification of Water-Extractable Organic Carbon from Thermally Heated Soils: C-13 NMR and Accurate Mass Analyses Find Benzene and Pyridine Carboxylic Acids.

To simulate the effects of wildfire on the combustion process in soils and their potential to leach organic compounds into streams and groundwater, mineral soil samples were heated at temperatures of 150-550 °C. Then, the soils were leached with deionized water, filtered, and analyzed for dissolved organic carbon. The water extract was concentrated by both XAD-8 and XAD-4 resins and analyzed by C-13 nuclear magnetic resonance and liquid chromatography time-of-flight mass spectrometry. Approximately 15-20% of the water-extractable organic carbon was identified as benzene dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acid isomers, commonly called BPCAs. Also identified were isomers of pyridine dicarboxylic acids and tricarboxylic acids (PCAs). The conversion of soil organic carbon to BPCAs occurs at 250 °C and reaches a maximum between 350 and 450 °C. At higher temperatures (>450 °C), the BPCA concentrations decrease, suggesting decarboxylation and conversion to carbon dioxide and water. This is the first report of BPCAs and PCAs in water-extractable organic carbon from thermally altered soil and suggest that these compounds are possible candidates for further water-quality studies in watersheds affected by wildfire. Finally, BPCAs and PCAs could contribute to the black carbon and nitrogen in seawater and are worthy of future investigation.

Identification of opioids in surface and wastewaters by LC/QTOF-MS using retrospective data analysis.

Opioids, both as prescription drugs and abuse substances, have been a hot topic and a focus of discussion in the media for the last few years. Although the literature published shows the occurrence of opioids and some of their metabolites in the aquatic environment, there are scarce data in the application of high resolution mass spectrometry (HRMS) for the analysis of these compounds in the environment. The use of HRMS allows increasing the number of opioids that can be studied as well as the detection of unknown opioids, their metabolites and potential transformation products. In this work, a retrospective analysis for the identification of opioids and their metabolites using a curated database was applied to surface water and wastewater samples taken in the state of Minnesota (U.S.) in 2009, which were previously analyzed by liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS) for antidepressants. The database comprised >200 opioids including natural opiates (e.g. morphine and codeine), their semi-synthetic derivatives (e.g. heroin, hydromorphone, hydrocodone, oxycodone, oxymorphone, meperidine and buprenorphine), fully synthetic opioids (e.g. fentanyl, methadone, tramadol, dextromethorphan and propoxyphene), as well as some of their metabolites (e.g. 6-monoacetylcodeine, dextrorphan, EDDP, normorphine and O-desmethyltramadol). Moreover, additional MS-MS experiments were performed to confirm their identification, as well as to recognize fragmentation patterns and diagnostic ions for several opioids. These data provide a better understanding of the historical occurrence of opioids and their metabolites in surface waters impacted by wastewater sources. The concentrations of individual opioids in surface water and wastewater effluent varied from 8.8 (EDDP) to 1640 (tramadol) ngL-1 and from 12 (dihydrocodeine) to 1288 (tramadol) ngL-1, respectively. The opioids with higher overall frequency detections were tramadol, dextromethorphan and its metabolite, dextrorphan.

Degradation of polyethylene glycols and polypropylene glycols in microcosms simulating a spill of produced water in shallow groundwater.

Polyethylene glycols (PEGs) and polypropylene glycols (PPGs) are frequently used in hydraulic fracturing fluids and have been detected in water returning to the surface from hydraulically fractured oil and gas wells in multiple basins. We identified degradation pathways and kinetics for PEGs and PPGs under conditions simulating a spill of produced water to shallow groundwater. Sediment-groundwater microcosm experiments were conducted using four produced water samples from two Denver-Julesburg Basin wells at early and late production. High-resolution mass spectrometry was used to identify the formation of mono- and di-carboxylated PEGs and mono-carboxylated PPGs, which are products of PEG and PPG biodegradation, respectively. Under oxic conditions, first-order half-lives were more rapid for PEGs (<0.4-1.1 d) compared to PPGs (2.5-14 d). PEG and PPG degradation corresponded to increased relative abundance of primary alcohol dehydrogenase genes predicted from metagenome analysis of the 16S rRNA gene. Further degradation was not observed under anoxic conditions. Our results provide insight into the differences between the degradation rates and pathways of PEGs and PPGs, which may be utilized to better characterize shallow groundwater contamination following a release of produced water.

Identification of Proprietary Amino Ethoxylates in Hydraulic Fracturing Wastewater Using Liquid Chromatography/Time-of-Flight Mass Spectrometry with Solid-Phase Extraction.

This work describes the discovery of amino-poly(ethylene glycol)s, amino-poly(ethylene glycol) carboxylates, and amino-poly(ethylene glycol) amines in 20 produced water samples from hydraulic fracturing in the western United States. These compounds, with masses in the range of m/ z 120-986, were identified using solid-phase extraction and liquid chromatography/quadrupole time-of-flight mass spectrometry. The polymeric sorbent, Oasis HLB, gave good recovery for all three ethoxylated surfactants and desalted the samples, which significantly reduced suppression of the mass spectral signal allowing detection and identification. The Kendrick mass defect, mass spectra, fragmentation pathways, and pure standards were used for confirmation. Finally, because these compounds are not explicitly listed in FracFocus reports, rather they are categorized as a proprietary surfactant blend; their identification is an important step in understanding the chemistry, treatment, and possible toxicity of hydraulic fracturing wastewater.

Organic Chemical Characterization and Mass Balance of a Hydraulically Fractured Well: From Fracturing Fluid to Produced Water over 405 Days.

A long-term field study (405 days) of a hydraulically fractured well from the Niobrara Formation in the Denver-Julesburg Basin was completed. Characterization of organic chemicals used in hydraulic fracturing and their changes through time, from the preinjected fracturing fluid to the produced water, was conducted. The characterization consisted of a mass balance by dissolved organic carbon (DOC), volatile organic analysis by gas chromatography/mass spectrometry, and nonvolatile organic analysis by liquid chromatography/mass spectrometry. DOC decreased from 1500 mg/L in initial flowback to 200 mg/L in the final produced water. Only ∼11% of the injected DOC returned by the end of the study, with this 11% representing a maximum fraction returned since the formation itself contributes DOC. Furthermore, the majority of returning DOC was of the hydrophilic fraction (60-85%). Volatile organic compound analysis revealed substantial concentrations of individual BTEX compounds (0.1-11 mg/L) over the 405-day study. Nonvolatile organic compounds identified were polyethylene glycols (PEGs), polypropylene glycols (PPG), linear alkyl-ethoxylates, and triisopropanolamine (TIPA). The distribution of PEGs, PPGs, and TIPA and their ubiquitous presence in our samples and the literature illustrate their potential as organic tracers for treatment operations or in the event of an environmental spill.

Inhibition of Biodegradation of Hydraulic Fracturing Compounds by Glutaraldehyde: Groundwater Column and Microcosm Experiments.

The rapid expansion of unconventional oil and gas development has raised concerns about the potential contamination of aquifers; however, the groundwater fate and transport of hydraulic fracturing fluid compounds and mixtures remains a significant data gap. Degradation kinetics of five hydraulic fracturing compounds (2-propanol, ethylene glycol, propargyl alcohol, 2-butoxyethanol, and 2-ethylhexanol) in the absence and presence of the biocide glutaraldehyde were investigated under a range of redox conditions using sediment-groundwater microcosms and flow-through columns. Microcosms were used to elucidate biodegradation inhibition at varying glutaraldehyde concentrations. In the absence of glutaraldehyde, half-lives ranged from 13 d to >93 d. Accurate mass spectrometry indicated that a trimer was the dominant aqueous-phase glutaraldehyde species. Microbial inhibition was observed at glutaraldehyde trimer concentrations as low as 5 mg L-1, which demonstrated that the trimer retained some biocidal activity. For most of the compounds, biodegradation rates slowed with increasing glutaraldehyde concentrations. For many of the compounds, degradation was faster in the columns than the microcosms. Four compounds (2-propanol, ethylene glycol, propargyl alcohol, and 2-butoxyethanol) were found to be both mobile and persistent in groundwater under a range of redox conditions. The glutaraldehyde trimer and 2-ethylhexanol were more rapidly degraded, particularly under oxic conditions.

Identification of polypropylene glycols and polyethylene glycol carboxylates in flowback and produced water from hydraulic fracturing.

The purpose of the study was to separate and identify the unknown surfactants present in flowback and produced water from oil and gas wells in the Denver-Julesburg Basin (Niobrara Formation) in Weld County, Colorado, USA. Weld County has been drilled extensively during the last five years for oil and gas between 7000-8000 feet below land-surface. Polypropylene glycols (PPGs) and polyethylene glycols carboxylates (PEG-Cs) were found for the first time in these flowback and produced water samples. These ethoxylated surfactants may be used as friction reducers, clay stabilizers, and surfactants. Ultrahigh-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UHPLC/QTOF-MS) was used to separate and identify the different classes of PPGs, PEG-Cs, and their isomers. The Kendrick mass scale was applied along with mass spectrometry/mass spectrometry (MS-MS) with accurate mass for rapid and unequivocal identification. The PPGs and their isomers occur at the ppm concentration range and may be useful as "fingerprints" of hydraulic-fracturing. Comparing these detections to the compounds used in the fracturing process from FracFocus 3.0 (https://fracfocus.org), it appears that both PPGs and polyethylene glycols (PEGs) are commonly named as additives, but the PEG-Cs have not been reported. The PEG-Cs may be trace impurities or degradation products of PEGs.

LC/QTOF-MS fragmentation of N-nitrosodimethylamine precursors in drinking water supplies is predictable and aids their identification.

N-Nitrosodimethylamine (NDMA) is carcinogenic in rodents and occurs in chloraminated drinking water and wastewater effluents. NDMA forms via reactions between chloramines and mostly unidentified, N-containing organic matter. We developed a mass spectrometry technique to identify NDMA precursors by analyzing 25 model compounds with LC/QTOF-MS. We searched isolates of 11 drinking water sources and 1 wastewater using a custom MATLAB® program and extracted ion chromatograms for two fragmentation patterns that were specific to the model compounds. Once a diagnostic fragment was discovered, we conducted MS/MS during a subsequent injection to confirm the precursor ion. Using non-target searches and two diagnostic fragmentation patterns, we discovered 158 potential NDMA precursors. Of these, 16 were identified using accurate mass combined with fragment and retention time matches of analytical standards when available. Five of these sixteen NDMA precursors were previously unidentified in the literature, three of which were metabolites of pharmaceuticals. Except methadone, the newly identified precursors all had NDMA molar yields of less than 5%, indicating that NDMA formation could be additive from multiple compounds, each with low yield. We demonstrate that the method is applicable to other disinfection by-product precursors by predicting and verifying the fragmentation patterns for one nitrosodiethylamine precursor.

Identification of Novel Perfluoroalkyl Ether Carboxylic Acids (PFECAs) and Sulfonic Acids (PFESAs) in Natural Waters Using Accurate Mass Time-of-Flight Mass Spectrometry (TOFMS).

Recent scientific scrutiny and concerns over exposure, toxicity, and risk have led to international regulatory efforts resulting in the reduction or elimination of certain perfluorinated compounds from various products and waste streams. Some manufacturers have started producing shorter chain per- and polyfluorinated compounds to try to reduce the potential for bioaccumulation in humans and wildlife. Some of these new compounds contain central ether oxygens or other minor modifications of traditional perfluorinated structures. At present, there has been very limited information published on these "replacement chemistries" in the peer-reviewed literature. In this study we used a time-of-flight mass spectrometry detector (LC-ESI-TOFMS) to identify fluorinated compounds in natural waters collected from locations with historical perfluorinated compound contamination. Our workflow for discovery of chemicals included sequential sampling of surface water for identification of potential sources, nontargeted TOFMS analysis, molecular feature extraction (MFE) of samples, and evaluation of features unique to the sample with source inputs. Specifically, compounds were tentatively identified by (1) accurate mass determination of parent and/or related adducts and fragments from in-source collision-induced dissociation (CID), (2) in-depth evaluation of in-source adducts formed during analysis, and (3) confirmation with authentic standards when available. We observed groups of compounds in homologous series that differed by multiples of CF2 (m/z 49.9968) or CF2O (m/z 65.9917). Compounds in each series were chromatographically separated and had comparable fragments and adducts produced during analysis. We detected 12 novel perfluoroalkyl ether carboxylic and sulfonic acids in surface water in North Carolina, USA using this approach. A key piece of evidence was the discovery of accurate mass in-source n-mer formation (H(+) and Na(+)) differing by m/z 21.9819, corresponding to the mass difference between the protonated and sodiated dimers.

Analysis of hydraulic fracturing additives by LC/Q-TOF-MS.

The chemical additives used in fracturing fluids can be used as tracers of water contamination caused by hydraulic fracturing operations. For this purpose, a complete chemical characterization is necessary using advanced analytical techniques. Liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC/Q-TOF-MS) was used to identify chemical additives present in flowback and produced waters. Accurate mass measurements of main ions and fragments were used to characterize the major components of fracking fluids. Sodium adducts turned out to be the main molecular adduct ions detected for some additives due to oxygen-rich structures. Among the classes of chemical components analyzed by mass spectrometry include gels (guar gum), biocides (glutaraldehyde and alkyl dimethyl benzyl ammonium chloride), and surfactants (cocamidopropyl dimethylamines, cocamidopropyl hydroxysultaines, and cocamidopropyl derivatives). The capabilities of accurate mass and MS-MS fragmentation are explored for the unequivocal identification of these compounds. A special emphasis is given to the mass spectrometry elucidation approaches used to identify a major class of hydraulic fracturing compounds, surfactants.

Characterization of hydraulic fracturing flowback water in Colorado: implications for water treatment.

A suite of analytical tools was applied to thoroughly analyze the chemical composition of an oil/gas well flowback water from the Denver-Julesburg (DJ) basin in Colorado, and the water quality data was translated to propose effective treatment solutions tailored to specific reuse goals. Analysis included bulk quality parameters, trace organic and inorganic constituents, and organic matter characterization. The flowback sample contained salts (TDS=22,500 mg/L), metals (e.g., iron at 81.4 mg/L) and high concentration of dissolved organic matter (DOC=590 mgC/L). The organic matter comprised fracturing fluid additives such as surfactants (e.g., linear alkyl ethoxylates) and high levels of acetic acid (an additives' degradation product), indicating the anthropogenic impact on this wastewater. Based on the water quality results and preliminary treatability tests, the removal of suspended solids and iron by aeration/precipitation (and/or filtration) followed by disinfection was identified as appropriate for flowback recycling in future fracturing operations. In addition to these treatments, a biological treatment (to remove dissolved organic matter) followed by reverse osmosis desalination was determined to be necessary to attain water quality standards appropriate for other water reuse options (e.g., crop irrigation). The study provides a framework for evaluating site-specific hydraulic fracturing wastewaters, proposing a suite of analytical methods for characterization, and a process for guiding the choice of a tailored treatment approach.

Full- and pilot-scale GAC adsorption of organic micropollutants.

Granular activated carbon (GAC) adsorption of 30 environmentally relevant micropollutants (MP) from four surface waters was investigated at the pilot-scale with empty bed contact times (EBCTs) of 7 and 15 min. An increase in background dissolved organic matter resulted in more and earlier MP breakthrough. Compared to an EBCT of 7 min, MP breakthrough at an EBCT of 15 min demonstrated 52% later breakthrough on average for five MPs on a throughput basis. A regression model was developed with data from three waters to predict MP throughput in bed volumes to 10% breakthrough (BV10%) based on the influent dissolved organic carbon concentration and the MP pH-dependent octanol-water partition coefficient, polarizability, and molecular volume. The regression model over predicted full-scale BV10% values when applied to a wastewater-water impacted water source and to GAC with a larger particle diameter, for which a particle size adjustment was able to account for most of the difference.

Degradation pathways of lamotrigine under advanced treatment by direct UV photolysis, hydroxyl radicals, and ozone.

Lamotrigine is recently recognized as a persistent pharmaceutical in the water environment and wastewater effluents. Its degradation was studied under UV and ozone advanced oxidation treatments with reaction kinetics of lamotrigine with ozone (≈4 M(-1)s(-1)), hydroxyl radical [(2.1 ± 0.3) × 10(9)M(-1)s(-1)] and by UV photolysis with low and medium pressure mercury vapor lamps [quantum yields ≈0 and (2.7 ± 0.4)× 10(-4) respectively] determined. All constants were measured at pH 6 and at temperature ≈20°C. The results indicate that lamotrigine is slow to respond to direct photolysis or oxidation by ozone and no attenuation of the contaminant is expected in UV or ozone disinfection applications. The compound reacts rapidly with hydroxyl radicals indicating that advanced oxidation processes would be effective for its treatment. Degradation products were identified under each treatment process using accurate mass time-of-flight spectrometry and pathways of decay were proposed. The main transformation pathways in each process were: dechlorination of the benzene ring during direct photolysis; hydroxyl group addition to the benzene ring during the reaction with hydroxyl radicals; and triazine ring opening after reaction with ozone. Different products that form in each process may be to a varying degree less environmentally stable than the parent lamotrigine. In addition, a novel method of ozone quenching without addition of salts is presented. The new quenching method would allow subsequent mass spectrometry analysis without a solid phase extraction clean-up step. The method involves raising the pH of the sample to approximately 10 for a few seconds and lowering it back and is therefore limited to applications for which temporary pH change is not expected to affect the outcome of the analysis.

Identification of prometon, deisopropylprometon, and hydroxyprometon in groundwater by high resolution liquid chromatography/mass spectrometry.

Prometon, a major soil sterilant, and its main transformation products, deisopropylprometon (N(2)-isopropyl-6-methoxy-1,3,5-triazine-2,4-diamine) and hydroxyprometon (4,6-bis(isopropylamino)-1,3,5-triazin-2-ol), were identified as the dominant triazine herbicides in groundwater samples from 51 locations in Colorado, USA, over a two-year time period. They were concentrated from water by solid phase extraction and detected using an ultrahigh pressure, liquid chromatography-quadrupole time of flight tandem mass spectrometry (UHPLC/QTOF-MS). The transformation products, deisopropylprometon and hydroxyprometon, were confirmed using MS-MS experiments. An original strategy was applied to form the degradation standards for deisopropylprometon and hydroxyprometon, which consisted of photo-degradation of prometon followed by MS-MS analysis. The concentration of prometon ranged from the detection limit of 3 ng·L(-1) to 87 ng·L(-1), hydroxyprometon ranged up to 50 ng·L(-1), and deisopropylprometon up to 100 ng·L(-1), with a frequency of detection of 80%, which was greater than the other triazines detected in the groundwater samples. A new ratio is proposed for prometon degradation called the "deisopropylprometon to prometon ratio" or the DIP ratio, as an indicator of prometon residence time in groundwater. Furthermore, these data suggest that prometon is more of an issue for groundwater contamination in urban areas rather than agricultural areas.