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.     

Application of liquid chromatography quadrupole time-of-flight mass spectrometry to the identification of acetamiprid transformation products generated under oxidative processes in different water matrices

This work allowed the identification of major transformation products (TPs) of acetamiprid (ACTM) during Fenton process. Acetamiprid is a chloronicotinoid insecticide widely used around the world for its characteristics (high insecticidal activity, good systemic properties, suitable field stability, etc.). The degradation of the parent molecule and the identification of the main TPs were evaluated in different water matrices (demineralized water and real agro-food industrial wastewater). TPs of acetamiprid generated by Fenton experiments were monitored and identified by liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC–QTOF–MS/MS). Up to 14 TPs were characterized based on the accurate mass of the molecular ion and fragment ions obtained in both full-scan and MS/MS modes. Most of them were eliminated after 75 min of treatment time in demineralized water. However, in real agro-food industrial wastewater, most of them were eliminated at 90 min of treatment time, demonstrating the influence of the matrix composition on the studied compound degradation.     

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-μL 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.     

Retrospective LC-QTOF-MS analysis searching for pharmaceutical metabolites in urban wastewater

The presence of pharmaceuticals in the environment is a matter of major concern because of their wide consumption and their potential negative effect on the water quality and living organisms. After human and/or veterinary consumption, pharmaceuticals can be excreted in unchanged form as the parent compound and/or as free or conjugated metabolites. These compounds seem not to be completely removed during wastewater treatments and might finally arrive to surface and ground waters. Consequently, both parent pharmaceuticals and metabolites are target analytes to be considered in analytical methodologies. The satisfactory sensitivity in full-acquisition mode, high-resolution, exact mass measurements and MS/MS capabilities of hybrid quadrupole time-of-flight (QTOF) mass spectrometry make of this technique a powerful analytical tool for the identification of organic contaminants. In this study, the use of QTOF-MS with the aid of specialised processing-data application managers has allowed the retrospective analysis of pharmaceuticals metabolites in urban wastewater without the need for additional injection of sample extracts. Around 160 metabolites have been investigated in wastewater samples previously analysed only for parent compounds using LC-QTOF under MS(E) mode (simultaneous recording of two acquisition functions, at low and high collision energy). The retrospective analysis was applied to search for pharmaceutical metabolites in parent-positive effluent wastewaters from the Spanish Mediterranean region. Five metabolites, such as clopidogrel carboxylic acid or N-desmethyl clarithromycin, were identified in the samples.     

Importance of MS selectivity and chromatographic separation in LC‐MS/MS‐based methods when investigating pharmaceutical metabolites in water. Dipyrone as a case of study

Pharmaceuticals are emerging contaminants of increasing concern because of their presence in the aquatic environment and potential to reach drinking‐water sources. After human and/or veterinary consumption, pharmaceuticals can be excreted in unchanged form, as the parent compound, and/or as free or conjugated metabolites. Determination of most pharmaceuticals and metabolites in the environment is commonly made by liquid chromatography (LC) coupled to mass spectrometry (MS). LC coupled to tandem MS is the technique of choice nowadays in this field. The acquisition of two selected reaction monitoring (SRM) transitions together with the retention time is the most widely accepted criterion for a safe quantification and confirmation assay. However, scarce attention is normally paid to the selectivity of the selected transitions as well as to the chromatographic separation. In this work, the importance of full spectrum acquisition high‐resolution MS data using a hybrid quadrupole time‐of‐flight analyser and/or a suitable chromatographic separation (to reduce the possibility of co‐eluting interferences) is highlighted when investigating pharmaceutical metabolites that share common fragment ions. For this purpose, the analytical challenge associated to the determination of metabolites of the widely used analgesic dipyrone (also known as metamizol) in urban wastewater is discussed. Examples are given on the possibilities of reporting false positives of dypirone metabolites by LC‐MS/MS under SRM mode due to a wrong assignment of identity of the compounds detected. Copyright © 2012 John Wiley & Sons, Ltd.     

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. Copyright © 2011 John Wiley & Sons, Ltd.     

Liquid chromatography time‐of‐flight mass spectrometry evaluation of fungicides reactivity in free chlorine containing water samples

Liquid chromatography (LC) combined with tandem mass spectrometry (MS/MS), based on the use of a hybrid quadrupole‐time‐of‐flight mass analyzer, was used to investigate the reactivity of nine fungicides in free chlorine‐containing water samples. Three of the selected compounds (fenhexamid, FEN; pyrimethanil, PYR; and cyprodinil, CYP) displayed a poor stability in presence of moderate chlorine levels; thus, the effects of different parameters on their half‐lives (t_1/2) were evaluated. Sample pH, bromide traces, and the water matrix affected their relative stabilities. Despite such variations, the three fungicides are degraded at significant rates not only in ultrapure, but also in surface water spiked with chlorine levels up to 2 µg ml^?1, and when mixed with chlorinated tap water, generating several transformation products (TPs). The time‐course of precursor species and their TPs was followed in the LC‐MS mode, using the information contained in accurate, full scan mass spectra (MS) to propose the empirical formulae of TPs. Thereafter, their ion product scan (MS/MS) spectra were considered to set their chemical structures; allowing, in some cases, to distinguish between isomeric TPs. The reaction pathway of FEN, the less stable fungicide, involved just an electrophilic substitution of hydrogen per chlorine, or bromine, and cleavage of the molecule to render an amide. PYR and CYP shared common reaction routes consisting of halogenation, hydroxylation, and condensation processes leading to complex mixtures of TPs, which were relatively stable to further transformations. Copyright © 2013 John Wiley & Sons, Ltd.     

Profiling of grape monoterpene glycosides (aroma precursors) by ultra‐high performance‐liquid chromatography‐high resolution mass spectrometry (UHPLC/QTOF)

A ‘suspect screening analysis’ method for grape metabolomics by ultra‐high performance‐liquid chromatography (UHPLC) and high‐resolution quadrupole‐time of flight (QTOF) mass spectrometry was recently developed. This method was applied to study grape monoterpene glycosides, the main grape aroma precursors. Since standard compounds were not available, they were tentatively identified by overlapping various analytical approaches, in agreement with the indications recommended in mass spectrometry (MS)‐based metabolomics. Accurate mass and isotopic pattern, MS/MS fragmentation, correlation between fragments observed and putative structures and between liquid chromatography coupled with mass spectrometry (LC/MS) and gas chromatography/mass spectrometry signals were studied. Seventeen monoterpene glycosides were identified without performing the hydrolytic artifacts commonly used to study these compounds which may affect sample profile. This is the first time that a detailed study of these aroma precursors has been carried out by direct LC/MS analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Joint MS‐based platforms for comprehensive comparison of rat plasma and serum metabolic profiling

Metabolomics is a rapidly growing field in the comprehensive understanding of cellular and organism‐specific responses associated with perturbations induced by medicines, chemicals and environment. Blood matrices are frequently used in clinical and biological studies. In this study, we compared metabolic profiling between rat plasma and serum using complementary platforms of gas chromatography–mass spectrometry (GC‐MS) and liquid chromatography–quadruple time‐of‐flight–mass spectrometry (LC‐QTOF‐MS). The sample types that were tested included plasma prepared with K₂EDTA and serum collected using venous blood collection protocols. The results of peak area variation for each detected metabolite/feature in the quality control samples showed a good reproducibility in LC‐QTOF‐MS and better reproducibility in GC‐MS. In GC‐MS analysis: (a) 25.8% of the defined metabolites differed serum from plasma profiling (t‐test, p < 0.05); and (b) serum possessed higher sensitivity than plasma for its generally higher peak intensity in the metabolic profiling. In LC‐QTOF‐MS analysis, 13 (in positive ion mode) and seven (in negative ion mode) important metabolites were identified as mainly contributing to the separation between serum and plasma. Copyright © 2014 John Wiley & Sons, Ltd.     

Behavior of amoxicillin in wastewater and river water: identification of its main transformation products by liquid chromatography/electrospray quadrupole time-of-flight mass spectrometry

The identification of transformation products (TPs) of pharmaceuticals in the environment is essentially a challenging task due to the lack of standards and the instrumental capabilities required to detect compounds (sometimes unknowns) that are produced under environmental conditions. In this work, we report the use of liquid chromatography/electrospray quadrupole time-of-flight mass spectrometry (LC/QTOF-MS/MS) as a tool for the identification of amoxicillin (AMX) and its main TPs in wastewater and river water samples. Laboratory degradation experiments of AMX were performed in both alkaline and acidic media in order to confirm that the expected transformation pathway in the aquatic media is through the β-lactam ring cleavage. A thorough study was carried out with both standards and real samples (wastewater and river water samples). Four compounds were identified as main TPs: both amoxicillin diketopiperacine-2',5' and amoxilloic acid diastereomers. Amoxilloic acid stereoisomers are reported for the first time in environmental matrices. The transformation product (5R)-amoxicillin diketopiperacine-2',5' was frequently detected in river waters. Besides, another AMX transformation product formed during analysis was also structurally elucidated for the first time (amoxicilloic acid methyl ester) via accurate mass measurements. Collected data show that although AMX is not present as such in environmental samples, different TPs occur. This study represent a valuable indicator of the potential of LC/QTOF-MS/MS for the identification and structural elucidation of TPs in the environment using accurate MS/MS experiments, enabling thus the recognition of the environmental transformation pathway.     

Simultaneous determination of acidic,neutral and basic pharmaceuticals in urban wastewater by ultra high-pressure liquid chromatography-tandem mass spectrometry

In this work, an ultra high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method has been developed for the simultaneous quantification and confirmation of the 20 most consumed pharmaceuticals in Spain in urban wastewater and surface water samples. The scope of the method included acidic, neutral and basic compounds belonging to different therapeutic classes and allows their simultaneous determination in just a single injection, giving realistic information of the most widely consumed pharmaceuticals in only one analysis. An enrichment step based on solid-phase extraction using Oasis HLB cartridges was carried out, followed by UHPLC-MS/MS measurement with a fast-acquisition triple quadrupole mass analyzer. It allowed working with short dwell times and made possible to acquire three simultaneous SRM transitions per compound to assure a reliable identification. Several isotope-labelled internal standards were used as surrogates to correct SPE losses, as well as matrix effects that notably affect quantification of analytes. The method was validated in surface water and effluent and influent urban wastewater at different concentrations from 0.005 μg/L (surface water) to 1.25 μg/L (influent wastewater). The optimized method was applied to the analysis of 84 urban wastewater samples (influent and effluent), with the result that 17 out of 20 compounds monitored were detected in the samples. Analgesics and anti-inflamatories, cholesterol lowering statin drugs and lipid regulators were the major groups found, with diclofenac, ketoprofen, naproxen, 4-aminoantipyrine, bezafibrate, gemfibrozil and venlafaxine being the most frequently detected. The highest concentration level reached was 277 μg/L for salicylic acid in influent wastewater.     

Mass spectrometry characterization of 3‐OH butyrated β‐cyclodextrin

Oligo(3‐OH butyrate)‐β‐cyclodextrin esters (PHB‐CD) were obtained through ring opening of β‐butyrolactone (β‐BL) in the presence of β‐cyclodextrin (CD) and (‐)‐sparteine (SP) as nucleophilic activator. The resulted reaction mixture was first separated in two fractions and then investigated through a deep mass spectrometry (MS) study performed on a liquid chromatography‐electrospray ionization‐quadrupole time of flight (LC‐ESI‐QTOF) instrument. LC MS and tandem MS structural assignment of the reaction products was completed by NMR. The performed analysis revealed that poly(3‐OH butyrate) homopolymers (PHB) are formed together with the PHB‐CD products. Secondary reactions resulting in the formation of crotonates were also proved to occur. A comparison between MS and NMR results demonstrated that more than one PHB oligomer is attached to the CD in the PHB‐CD product. The tandem MS fragmentation studies validated the proposed structure of CD derivatives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Evaluation of multiple alternative instrument platforms for targeted and non‐targeted dioxin and furan analysis

The use of gas chromatography coupled to high‐resolution magnetic sector mass spectrometers (GC‐HRMS) is well established for dioxin and furan analysis. However, the use of gas chromatography coupled to triple quadrupole (MS/MS) and time of flight (TOF) mass spectrometers with atmospheric pressure ionization (API) and traditional electron ionization (EI) for dioxin and furan analysis is emerging as a viable alternative to GC‐HRMS screening. These instruments offer greater versatility in the lab for a wider range of compound identification and quantification as well as improved ease of operation. The instruments utilized in this study included 2 API‐MS/MS, 1 traditional EI‐MS/MS, an API‐quadrupole time of flight mass spectrometer (API‐QTOF), and a EI‐high‐resolution TOF (EI‐HRTOF). This study compared these 5 instruments to a GC‐HRMS using method detection limit (MDLs) samples for dioxin and furan analysis. Each instrument demonstrated acceptable MDL values for the 17 chlorinated dioxin and furans studied. The API‐MS/MS instruments provide the greatest overall improvement in MDL value over the GC‐HRMS with a 1.5 to 2‐fold improvement. The API‐QTOF and EI‐TOF demonstrate slight increases in MDL value as compared with the GC‐HRMS with a 1.5‐fold increase. The 5 instruments studied all demonstrate acceptable MDL values with no MDL for a single congener greater than 5 times that for the GC‐HRMS. All 5 instruments offer a viable alternative to GC‐HRMS for the analysis of dioxins and furans and should be considered when developing new validated methodologies.     

The use of high performance liquid chromatography-quadrupole time-of-flight mass spectrometry coupled to advanced data mining and chemometric tools for discrimination and classification of red wines according to their variety

In this study, the potential of high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (HPLC–QTOFMS) for metabolomic profiling of red wine samples was examined. Fifty one wines representing three varieties (Cabernet Sauvignon, Merlot, and Pinot Noir) of various geographical origins were sourced from the European and US retail market. To find compounds detected in analyzed samples, an automated compound (feature) extraction algorithm was employed for processing background subtracted single MS data. Stepwise reduction of the data dimensionality was followed by principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA) which were employed to explore the structure of the data and construct classification models. The validated PLS-DA model based on data recorded in positive ionization mode enabled correct classification of 96% of samples. Determination of molecular formula and tentative identification of marker compound was carried out using accurate mass measurement of full single MS spectra. Additional information was obtained by correlating the fragments obtained by MS/MS accurate mass spectra using the QTOF with collision induced dissociation (CID) of precursor ions.     

Analysis of phenolic choline esters from seeds of Arabidopsis thaliana and Brassica napus by capillary liquid chromatography/electrospray‐ tandem mass spectrometry

Total phenolic choline ester fractions prepared from seeds of Arabidopsis thaliana and Brassica napus were analyzed by capillary LC/ESI‐QTOF‐MS and direct infusion ESI‐FTICR‐MS. In addition to the dominating sinapoylcholine, 30 phenolic choline esters could be identified based on accurate mass measurements, interpretation of collision‐induced dissociation (CID) mass spectra, and synthesis of selected representatives. The compounds identified so far include substituted hydroxycinnamoyl‐ and hydroxybenzoylcholines, respective monohexosides as well as oxidative coupling products of phenolic choline esters and monolignols. Phenolic choline esters are well separable by reversed‐phase liquid chromatography and sensitively detectable using electrospray ionization mass spectrometry in positive ion mode. CID mass spectra obtained from molecular ions facilitate the characterization of both the type and substitution pattern of such compounds. Therefore, LC/ESI‐MS/MS represents a valuable tool for comprehensive qualitative and quantitative analysis of this compound class. Copyright © 2008 John Wiley & Sons, Ltd.     

Application of gas and liquid chromatography coupled to time‐of‐flight mass spectrometry in pesticides: Multiresidue analysis

Analysis of pesticide residues in water and food matrices is an active research area closely related to food safety and environmental issues. In this aspect mass spectrometry (MS) coupled to gas chromatography (GC) and liquid chromatography (LC) has been increasingly used in the analysis of pesticide residues in water and food. The increasing interest in application of high‐resolution mass spectrometry with time‐of‐flight (TOF) and hybrid triple quadrupole TOF in pesticide analysis is due to its capability of performing both targeted and nontargeted analysis. This article discusses an overview of the application of GC‐TOF‐MS and LC‐TOF‐MS in water and food matrices.     

Chip‐based high resolution tandem mass spectrometric determination of fibroblast growth factor—chondroitin sulfate disaccharides noncovalent interaction

Fibroblast growth factor‐2 (FGF‐2) is involved in wound healing and embryonic development. Glycosaminoglycans (GAGs), the major components of the extracellular matrix (ECM), play fundamental roles at this level. FGF‐GAG noncovalent interactions are in the focus of research, due to their influence upon cell proliferation and tissue regeneration. Lately, high resolution mass spectrometry (MS) coupled with chip‐nanoelectrospray (nanoESI) contributed a significant progress in glycosaminoglycomics by discoveries related to novel species and their characterization. We have employed a fully automated chip‐nanoESI coupled to a quadrupole time‐of‐flight (QTOF) MS for assessing FGF‐GAG noncovalent complexes. For the first time, a CS disaccharide was involved in a binding assay with FGF‐2. The experiments were conducted in 10 mM ammonium acetate/formic acid, pH 6.8, by incubating FGF‐2 and CS in buffer. The detected complexes were characterized by top‐down in tandem MS (MS/MS) using collision induced‐dissociation (CID). CID MS/MS provided data showing for the first time that the binding process occurs via the sulfate group located at C4 in GalNAc. This study has demonstrated that chip‐MS may generate reliable data upon the formation of GAG‐protein complexes and their structure. Biologically, the findings are relevant for studies focused on the identification of the active domains in longer GAG chains.     

Quadrupole‐time‐of‐flight mass spectrometry screening for synthetic cannabinoids in herbal blends

‘Legal highs’ are novel substances which are intended to elicit a psychoactive response. They are sold from ‘head shops’, the internet and from street suppliers and may be possessed without legal restriction. Several months ago, a 19‐year‐old woman came searching for medical treatment as she had health problems caused by smoking legal highs. The substances were sold as herbal blends in plastic bags under four different labels. In this work, samples of these herbal blends have been analysed to investigate the presence of psychoactive substances without any reference standard being available at the laboratory. A screening strategy for a large number of synthetic and natural cannabinoids has been applied based on the use of ultra‐high pressure liquid chromatography coupled to quadrupole‐time of flight mass spectrometry (UHPLC‐QTOF MS) under MS^E mode. A customized home‐made database containing literature‐based exact masses for parent and product ions of around 200 synthetic and natural cannabinoids was compiled. The presence of the (de)protonated molecule measured at its accurate mass was evaluated in the samples. When a peak was detected, collision‐induced dissociation fragments and characteristic isotopic ions were also evaluated and used for tentative identification. After this tentative identification, four synthetic cannabinoids (JWH‐081, JWH‐250, JWH‐203 and JWH‐019) were unequivocally confirmed by subsequent acquisition of reference standards. The presence in the herbal blends of these synthetic cannabinoids might explain the psychotic and catatonic symptoms observed in the patient, as JWH compounds could act as potent agonists of CB₁ and CB₂ receptors located in the Limbic System and Basal ganglia of the human brain. Copyright © 2013 John Wiley & Sons, Ltd.     

Screening for pharmaceutical transformation products formed in river sediment by combining ultrahigh performance liquid chromatography/high resolution mass spectrometry with a rapid data-processing method

While the occurrence of pharmaceuticals in the aquatic environment has been extensively investigated, their environmental fate is less thoroughly explored. Scarce information on their transformation pathways and transformation products (TPs) limits conventional target analytical approaches. In this study, samples from water/sediment tests were analyzed by ultrahigh performance liquid chromatography interfaced with quadrupole time-of-flight mass spectrometry (UHPLC/QToF-MS). A data processing method based on peak detection, time-trend filtration and structure assignment was established to provide an efficient way for identifying the key TPs in terms of persistence; all software used for the individual steps of this method is freely available. The accurate mass and meaningful time-trends were major contributors in facilitating the isolation of plausible TP peaks. In total, 16 TPs from 9 parent pharmaceuticals were identified. Eleven out of the 16 TPs were confirmed by corresponding reference standards; no standards were available for the remaining TPs. For additional 6 potential TPs, a molecular formula was suggested but no additional structural information could be generated. Among the TPs identified in the water/sediment tests, carbamazepine-10,11-epoxide (parent: carbamazepine), saluamine (parent: furosemide), chlorothiazide and 4-amino-6-chloro-1,3-benzenedisulfonamide (parent of both: hydrochlorothiazide), and 1-naphthol (parent: propranolol) accumulated over the entire incubation period of 35 days.     

Application of ultra-high-pressure liquid chromatography–tandem mass spectrometry to the determination of multi-class pesticides in environmental and wastewater samples: Study of matrix effects

An ultra-high-pressure liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method for the determination of 37 pesticides (herbicides, insecticides and fungicides) in environmental and wastewater has been developed. To efficiently combine UHPLC with MS/MS, a fast-acquisition triple quadrupole mass analyzer was used. This analyzer (minimum dwell time, 5 ms) allows acquiring up to three simultaneous transitions in the selected reaction monitoring mode for each compound assuring a reliable identification without resolution or sensitivity losses. A pre-concentration step based on solid-phase extraction using Waters Oasis HLB cartridges (0.2 g) was applied with a 100-fold pre-concentration factor along the whole analytical procedure. The method was validated based on European SANCO guidelines using surface, ground, drinking and treated water (from an urban solid residues treatment plant) spiked at two concentration levels (0.025 and 0.1 μg/L), the lowest having been established as the limit of quantification objective. The method showed excellent sensitivity, with instrumental limits of detection ranging from 0.1 to 7 pg. It was applied to environmental water samples (ground and surface water) as well as to samples of urban solid waste leachates (raw leachate and treated leachate after applying reversed osmosis) collected from a municipal treatment plant. Matrix effects have been studied in the different types of water samples analyzed, and several isotope-labelled internal standards have been evaluated as a way to compensate the signal suppression observed for most of the compounds studied, especially in wastewater samples. As a general remark, only those pesticides which response was corrected using their own isotope-labelled molecule, could be satisfactorily corrected in all type of samples, assuring in this way the accurate quantification in all matrix samples.