LC TOF-MS Research Articles

Conductive-diamond electrochemical oxidation of chlorpyrifos in wastewater and identification of its main degradation products by LC–TOFMS

The electrochemical transformation of the organophosphorous insecticide chlorpyrifos (CPF) was investigated in wastewater. The oxidation of CPF was carried out in a single-compartment electrochemical flow cell working under batch operation mode, using diamond-based material as anode and stainless steel as cathode. In order to evaluate its persistence and degradation pathway, two different concentration levels (1.0mgL−1 and 0.1mgL−1) were studied. Liquid chromatography/mass spectrometry was used for evaluation of the initial and electrolyzed solutions. The identification of CPF transformation products was performed by liquid chromatography–time of flight-mass spectrometry (LC–TOFMS). Results showed that CPF is completely removed at the end of treatment time. Analysis by LC–TOFMS allowed the identification of six degradation products (with Mw 154, 170, 197, 305 321 and 333). Three of the identified intermediates (Mw 170, 305 and 321) were completely removed at the end of electrolysis time. Interestingly, the formation of diethyl 3,5,6-trichloropyridin-2yl phosphate (chlorpyrifos oxon) and 3,5,6-trichloropyridin-2-ol was also found in previous reported degradation pathways using different degradation technologies.

Pigmentation and Spectral Absorbance Signatures in Deep-Water Corals from the Trondheimsfjord, Norway

The pigmentation and corresponding in vivo and in vitro absorption characteristics in three different deep-water coral species: white and orange Lophelia pertusa, Paragorgia arborea and Primnoa resedaeformis, collected from the Trondheimsfjord are described. Pigments were isolated and characterized by High-Performance Liquid Chromatography (HPLC) analysis and High-Performance Liquid Chromatography Time-Of-Flight Mass Spectrometer (LC-TOF MS). The main carotenoids identified for all three coral species were astaxanthin and a canthaxanthin-like carotenoid. Soft tissue and skeleton of orange L. pertusa contained 2 times more astaxanthin g−1 wet weight compared to white L. pertusa. White and orange L. pertusa were characterized with in vivo absorbance peaks at 409 and 473 nm, respectively. In vivo absorbance maxima for P. arborea and P. resedaeformis was typically at 475 nm. The shapes of the absorbance spectra (400–700 nm) were species-specific, indicated by in vivo, in vitro and the corresponding difference spectra. The results may provide important chemotaxonomic information for pigment when bonded to their proteins in vivo, bio-prospecting, and for in situ identification, mapping and monitoring of corals.

Photolysis of flumequine: Identification of the major phototransformation products and toxicity measures

Direct photolysis of flumequine (FLU, 20mgL−1) in different types of water (demineralised water (DW) and synthetic seawater (SW)), was conducted in a Suntest CPS+solar simulator to evaluate its persistence and toxicity, and to identify the major phototransformation products (PTPs) generated during photolysis in DW. It was observed that FLU is susceptible to transformation when subjected to direct solar radiation. The composition of the water affects the FLU degradation kinetics, which is slower in SW. Photolytic transformation products generated during direct photolysis were identified by liquid chromatography–time of flight–mass spectrometry (LC–TOF–MS). Fourteen PTPs generated in DW were identified. The transformation of FLU begins with the opening of the heterocyclic ring by oxidation of the double bond. Loss of the fluorine atom and the hydroxylation of the aromatic ring also appear as the majority, especially in the early stages. Comparative acute toxicity evaluation by Vibrio fischeri and Daphnia magna bioassays was performed for the first and last irradiated solutions in both matrices studied. These bioassays demonstrated that in the SW matrix, the most persistent PTPs are highly toxic to D. magna but less so to V. fischeri.

LC Coupled with TOFMS for Metabonomics Study of Mini-pigs with Atherosclerosis

In this study, serum metabolic profiles of mini-pigs with atherosclerosis (AS) were analyzed by LC–TOFMS. Partial least-squares to latent structure-discriminant analysis and orthogonal projection to latent structure-discriminant analysis were used for group differentiation and selection of potential biomarkers. The mini-pig disease models were constructed by feeding a high-fat diet and inducing coronary injury, in accordance with the mechanism of AS pathogenesis. To characterize the development of AS, serum samples were collected and analyzed at two time points (two and ten weeks). Separate distinct clustering of results from normal and model mini-pigs could be observed for both the two and ten-week samples. With the development of AS, the metabolism of the model mini-pigs was more substantially disturbed. Major metabolites contributing to the discrimination were fatty acids, lysophosphatidylcholines, and bile acids. These potential biomarkers are related with inflammation, oxidative stress, and abnormal lipid and energy metabolism.

Formation of chlorinated by-products during photo-Fenton degradation of pyrimethanil under saline conditions. Influence on toxicity and biodegradability

This study evaluated the formation of chlorinated transformation products during photo-Fenton treatment of pyrimethanil (PYR-20mgL−1) in two water matrices, demineralised water (DW) and water containing 5gL−1 of NaCl (DWNaCl). All experiments were carried out in compound parabolic collectors (CPC) at an initial Fe2+ concentration of 5mgL−1 and H2O2 concentration of 150–350mgL−1. Dissolved Organic Carbon (DOC), High-Performance Liquid Chromatography with Diode-Array Detection (HPLC–DAD), Liquid Chromatography–Time-Of-Flight Mass Spectrometry (LC–TOF-MS), toxicity and biodegradability tests were conducted to control the photocatalytic treatment. In DW, PYR was completely eliminated after 11.8min of illumination and initial DOC was reduced 50% after 79min of illumination with 33mM of H2O2 consumed. On the other hand, in DWNaCl water matrix, the same reduction in DOC took 110min of illumination and H2O2 consumption of 39mM, and total degradation of PYR was observed at 12min of illumination. PYR transformation products (TPs) were identified by LC–TOF-MS. It was demonstrated that photo-Fenton in a DWNaCl produces some chlorinated TPs in addition to the non-chlorinated TPs identified during degradation in the DW. All TPs formed were eliminated during photo-Fenton. Additionally, the presence of chlorinated TPs does not increase the toxicity of the water, and TPs formed are more biodegradable than PYR.

Comparison of indirect and direct quantification of esters of monochloropropanediol in vegetable oil

The presence of fatty acid esters of monochloropropanediol (MEs) in food is a recent concern raised due to the carcinogenicity of their hydrolysable moieties 2- and 3-monochloropropanediol (2- and 3-MCPD). Several indirect methods for the quantification of MEs have been developed and are commonly in use until today, however significant discrepancies among analytical results obtained are challenging their reliability. The aim of the present study was therefore to test the trueness of an indirect method by comparing it to a newly developed direct method using palm oil and palm olein as examples. The indirect method was based on ester cleavage under acidic conditions, derivatization of the liberated 2- and 3-MCPD with heptafluorobutyryl imidazole and GC–MS determination. The direct method was comprised of two extraction procedures targeting 2-and 3-MCPD mono esters (co-extracting as well glycidyl esters) by the use of double solid phase extraction (SPE), and 2- and 3-MCPD di-esters by the use of silica gel column, respectively. Detection was carried out by liquid chromatography coupled to time of flight mass spectrometry (LC–ToF-MS). Accurate quantification of the intact compounds was assured by means of matrix matched standard addition on extracts. Analysis of 22 palm oil and 7 palm olein samples (2- plus 3-MCPD contamination ranged from 0.3 to 8.8μg/g) by both methods revealed no significant bias. Both methods were therefore considered as comparable in terms of results; however the indirect method was shown to require less analytical standards, being less tedious and furthermore applicable to all type of different vegetable oils and hence recommended for routine application.

Identification of phase I metabolites of cardiovascular and anti-ulcer drugs in surface water samples with liquid-chromatography–mass spectrometry methods

In our study we have identified phase I metabolites of cardiovascular and anti-ulcer agents with the application of predictive multiple reaction monitoring (pMRM) methods with liquid-chromatography–triple-quadrupole mass spectrometry (LC–QQQ-MS) in surface water samples. Targeted accurate mass spectrometry measurements were also carried out for confirmation with liquid-chromatography–time-of-flight mass spectrometry (LC–TOF-MS). pMRM followed by a targeted accurate mass spectrometry measurement can provide a sound basis for the selection of metabolites to be included in analytical methods for the investigation of environmental load of pharmaceuticals. Using LC–QQQ-MS twenty-one metabolites could be identified with two independent transitions at the same retention time and six of them could also be confirmed with LC–TOF-MS.

Multi-residue method for the analysis of synthetic surfactants and their degradation metabolites in aquatic systems by liquid chromatography–time-of-flight-mass spectrometry

Synthetic surfactants are economically important chemicals, as they are widely used in household cleaning detergents, textiles, paints, polymers and personal care products. In this work we have developed a method capable of the isolation and analysis of the most widely used surfactants (linear alkylbenzene sulfonates, LAS, nonylphenol ethoxylates, NPEO, and alcohol ethoxylates, AEO) and their main degradation products (sulfophenyl carboxylic acids, SPC, nonylphenol ethoxycarboxylates, NPEC, and polyethylene glycols, PEG) in aqueous and solid environmental matrices. First, analytes were extracted by ultrasonic extraction from sediments and suspended solids using methanol at 50 °C as solvent and 3 cycles (30 min per cycle). Clean-up and pre-concentration of the extracts and water samples were carried out by solid-phase extraction (SPE), using Oasis HLB cartridges. Recoveries were generally about 80% for most compounds. Identification and quantification of target compounds were performed by liquid chromatography–time-of-flight-mass spectrometry (LC–ToF-MS), which has been much less used in the field of environmental analysis than other MS techniques. Examples which illustrate the possible advantages of this technique for multi-analyte analysis of target and non-target contaminants in environmental samples are provided. Finally, the methodology developed here was validated by measuring the concentration of surfactants and their metabolites in selected marine sediment and seawater samples collected in Long Island Sound (NY), and in influent and effluent wastewater from Stony Brook treatment plant (NY). This paper presents some of the first data relative to the occurrence of PEG in the environment, especially in sediments where concentrations were generally higher (up to 1490 μg/kg) than those for other classes of targeted surfactants and their metabolites.

Direct Determination of MCPD Fatty Acid Esters and Glycidyl Fatty Acid Esters in Vegetable Oils by LC–TOFMS

Analysis of MCPD esters and glycidyl esters in vegetable oils using the indirect method proposed by the DGF gave inconsistent results when salting out conditions were varied. Subsequent investigation showed that the method was destroying and reforming MCPD during the analysis. An LC time of flight MS method was developed for direct analysis of both MCPD esters and glycidyl esters in vegetable oils. The results of the LC–TOFMS method were compared with the DGF method. The DGF method consistently gave results that were greater than the LC–TOFMS method. The levels of MCPD esters and glycidyl esters found in a variety of vegetable oils are reported. MCPD monoesters were not found in any oil samples. MCPD diesters were found only in samples containing palm oil, and were not present in all palm oil samples. Glycidyl esters were found in a wide variety of oils. Some processing conditions that influence the concentration of MCPD esters and glycidyl esters are discussed.

Screening and Identification of Many of the Compounds Present in Rauvolfia verticillata by Use of High-Pressure LC and Quadrupole TOF MS

A simple approach is described for LC–Q-TOFMS screening and identification of many of the compounds present in Rauvolfia verticillata. Combined isolation and identification of the complex chemical composition was conducted when investigating traditional Chinese medicine. Twenty-two components of Rauvolfia verticillata were identified by comparing retention times and molecular weights with those of available standards and with reference data. This study provided a rapid, sensitive, economical, and systematic method for identification and evaluation of the quality of complex traditional Chinese medicines.

Application of LC–TOF MS to analysis of hemoglobin acetaldehyde adducts in alcohol detoxification patients

Acetaldehyde adducts of hemoglobin have been regarded as potential biochemical markers of alcohol exposure. In this study a novel sensitive method using liquid chromatography coupled to time-of-flight mass spectrometry (LC-TOF MS) has been used to investigate changes in adduct levels in alcohol detoxification patients. Hemoglobin and authentic blood samples from 66 adults with an alcohol-dependence syndrome and from 12 children were analyzed for acetaldehyde modifications with and without trypsin digestion using LC-TOF MS. After in-vitro incubation of hemoglobin with increasing concentrations of acetaldehyde, followed by tryptic digestion, 21 modified peptide fragments could be identified from their accurate mass and retention time shift. Eight of these could also be detected in authentic human blood samples. Trace amounts in children's blood were indicative of an endogenous source. Modified peptide levels in patients' samples with and without ethanol were significantly different, as also were levels in samples from admission and from five days later. Samples obtained 5, 10, or 15 days after admission did not differ in adduct levels. The LC-TOF MS method was sensitive enough to detect acetaldehyde-modified hemoglobin peptides in blood samples from patients with an alcohol-dependence syndrome. However, elevated levels were only observed after recent ethanol consumption and decreased during five days of abstinence, suggesting that acetaldehyde-modified tryptic peptides of hemoglobin are potential biomarkers only for short-term ethanol ingestion.

Mass Spectrometry: Fourth conference of the Spanish Society of Mass Spectrometry (SEEM)

The Spanish Society of Mass Spectrometry (SEEM) held its first conference in Madrid in 2002. The second and third conferences took place in Barcelona and Oviedo in 2004 and 2006, respectively. Castellon was the city chosen to host the fourth biennial conference of SEEM (4RSEEM) from 30 September to 2 October 2009. The meeting was organized by the Research Institute for Pesticides and Water (IUPA), from University Jaume I, under the auspices of the President of the Organizing Committee, Felix Hernandez, Director of IUPA. SEEM is a rather young society, but a very active one thanks to the numerous prestigious scientists with considerable experience in mass spectrometry among its members. The series of conferences has become a meeting point for the growing community of Spanish mass spectrometrists, fostering discussions, exchanging experiences, and improving knowledge of mass spectrometry. The main objective of this conference series is to present relevant applications and to illustrate the impact of mass spectrometry in different applied areas. Accordingly, there were sessions on environmental and food analysis, bioanalysis, proteomic and metabolomic studies, elemental analysis, speciation and isotopic analysis, and fundamentals. It is worth mentioning that the number of international attendees is growing with every event. The conference was attended by more than 150 scientists, including about 50 young researchers (Ph.D. students and postdoctoral researchers) from about ten countries. The scientific program included a plenary lecture given by Emilio Gelpi (CSIC, Barcelona), who presented an interesting overview entitled the “History of mass spectrometry in Spain.” Eight keynote lectures were also presented by invited speakers: “Environmental mass spectrometry” by Susan Richardson (EPA, USA); “Investigation of phytoestrogens in food and water by LC-TOF MS” by Imma Ferrer (University of Colorado, USA); “Confident assignment of post-translational modifications using topdown mass spectrometry” by Julian Whitelegge (UCLA, USA); “Detection of anabolic steriods in doping control analysis. Present and future of LC-MS/MS” by Oscar Pozo (University of Ghent, Belgium); “Applications of mass spectrometry in metabolomics: from toxicology to disease diagnosis” by Elizabeth Want (Imperial College London, UK); “LC-MS in drug metabolite identification” by Wilfried Niessen (hyphen MassSpec, The Netherlands); “Organic isotope dilution analysis revisited: minimal labelling, heteroatom labelling and absolute determinations” by Jose Ignacio Garcia-Alonso (University of Oviedo, Spain); and “Theory and practice of orbitrap mass spectrometry” by Alexander Makarov (Thermo Instruments, Germany). In addition, 20 oral presentations were also selected, and around 80 posters were presented during F. Hernandez (*) Laboratorio de Analisis de Residuos de Plaguicidas (LARP), Instituto Universitario de Plaguicidas y Aguas (IUPA), Universitat Jaume I, 12071 Castellon de la Plana, Spain e-mail: hernandf@qfa.uji.es

A validated analytical method for the determination of perfluorinated compounds in surface-, sea- and sewagewater using liquid chromatography coupled to time-of-flight mass spectrometry

Perfluorinated compounds (PFCs), which are extensively used in a wide variety of applications because of their specific surfactant properties, have recently appeared as an important new class of global environmental pollutants. Quantitative analysis of PFCs in aqueous matrices remains, however, a challenging task. During this study, a new analytical method for the determination of 14 PFCs in surface-, sewage- and seawater was developed and validated. The target analytes were extracted using solid-phase extraction followed by liquid chromatography coupled to a time-of-flight mass spectrometer (LC–ToF-MS). The use of very narrow mass tolerance windows (<10 ppm) resulted in a highly selective MS-technique for the detection of PFCs in complex aqueous matrices. Validation of this analytical method in surface-, sewage- and seawater resulted in limits of quantification (LOQs) varying from 2 to 200 ng L −1, satisfying recoveries (92–134%), and good linearity ( R 2 = 0.99 for most analytes). Analysis of samples of the North Sea, the Scheldt estuary, and three harbours of the Belgian coastal region led to the detection of four different PFCs. Perfluorooctane sulfonate (PFOS) was found to be the most abundant PFC in levels up to 38.9 ng L −1.

Evaluation of two sample treatment methodologies for large-scale pesticide residue analysis in olive oil by fast liquid chromatography–electrospray mass spectrometry

In this study, a comprehensive evaluation of two simple sample treatment methodologies has been carried out for the development of large-scale multi-residue methods for pesticide testing in olive oil. The proposed methodologies are based on (a) liquid–liquid partitioning with acetonitrile followed by dispersive solid-phase extraction clean-up using graphitized carbon black, primary-secondary amine and C 18 sorbents; (b) liquid partitioning with acetonitrile saturated with petroleum ether followed by matrix solid-phase dispersion (MSPD) using aminopropyl as sorbent material and a Florisil cartridge for final clean-up in the elution step. To evaluate the proposed sample treatment methodologies, 105 representative multi-class pesticides were studied using fast liquid chromatography–electrospray time-of-flight mass spectrometry (LC–TOFMS). For validation purposes, recoveries studies were carried out at 10 and 100 μg kg −1 levels, yielding recovery rates in the range 70–130% for 72% of analytes using liquid–liquid procedure and for 57% analytes using MSPD procedure. The LC–MS method provided good linearity, precision and accuracy. The limits of detection obtained were lower than 10 μg kg −1 for more than 85% analytes using both sample treatment methodologies. In addition, minor matrix effects (i.e. signal suppression or enhancement ≤20%) were observed in ca. 70% of the studied compounds. Data obtained shows that both sample treatment methodologies proposed can be successfully applied for large-scale pesticide testing in olive oil samples, showing the ability to quickly detect trace amount of over one hundred target species with different physicochemical properties, without requiring expensive instrumentation for sample treatment step and involving relatively low amounts of solvent consumption and waste generation.

LC tandem MS and TOF MS: A new paradigm for emergency department drug testing

LC tandem MS and TOF MS: A new paradigm for emergency department drug testing

Discovering Sudan IV in Salty Eggs with LC–TOF-MS

This study evaluated the screening of Sudan dyes in salty egg using liquid chromatography/time-of-flight mass spectrometry (LC–TOF-MS). With this technology, accurate mass measurements were made to generate elemental compositions of ions and to provide complementary structural information. This approach is useful for the elucidation of organic pollutants at trace levels in complex food extracts and in the present study salty egg samples were analyzed for the presence of Sudan IV. TOF accurate mass elemental composition data of Sudan IV were found to be crucial for structural elucidation which was applied to the investigation of nine salty egg samples.

Photodegradation of sulfamethoxazole in various aqueous media: Persistence, toxicity and photoproducts assessment

The photochemical transformation of sulfamethoxazole (SMX) was investigated in different water matrices: distilled water (DW), distilled water + nitrate (10 and 20 mg L −1) and seawater (SW) to evaluate its persistence, toxicity and degradation pathway. A solar simulator Suntest CPS+ was used for the irradiation experiments. Identification of transformation products was performed in DW by liquid chromatography-time of flight-mass spectrometry (LC–TOF–MS). Acute toxicity of irradiated solutions was monitored by Vibrio fischeri and Daphnia magna bioassays in DW. Differences in the degradation rates were observed between DW and SW, being slower in SW. Presence of nitrate (indirect photolysis) in distilled water did not affect SMX degradation rate. No dissolved organic carbon (DOC) removal was observed in any case, thus indicating the formation of abundant transformation products (TPs). Analysis by LC–TOF–MS allowed the identification of up to nine transformation products during photolysis in DW. Only three of them had been previously reported in the literature, detected with other techniques. The cleavage of the sulfonamide bond and the photoisomerization by rearrangement of the isoxazole ring represent the main pathways, at the time that generate the most abundant and persistent intermediates. The acute toxicity of SMX solution varied according to test organisms. Daphnia magna was the most sensitive showing an increase from 60% to 100% immobilization after 30 h of irradiation when depletion of SMX was achieved, thus indicating the higher toxicity of the phototransformation products generated.

Structure determination and sensory evaluation of novel bitter compounds formed from β-acids of hop (Humulus lupulus L.) upon wort boiling

Abstract In order to screen for the bitter compounds generated from hop-derived precursors during the wort boiling process, an ethanolic hop extract was fractionated; the fractions obtained were thermally treated under model wort boiling conditions and, then, sensorially evaluated for their bitterness. Besides the isomerisation of the α-acids into the intensely bitter iso-α-acids, the bitterness of the fraction containing the β-acids was also found to be enhanced after wort boiling. To gain first insights into the β-acid-derived bitter compounds, the β-acid colupulone was isolated, thermally treated under wort boiling conditions and, then, investigated for bitter tasting degradation products by means of a taste dilution analysis (TDA). Besides the cohulupone, five previously unreported bitter-tasting colupulone degradation products, all of which exhibited a lingering, β-acid-like bitter taste with low recognition thresholds between 37.9 and 90.3 μmol/l, were isolated and their structures determined as two tricyclocolupone epimers, two dehydrotricyclocolupone epimers, and nortricyclocolupone, respectively, by means of LC–TOF–MS and 1D/2D-NMR spectroscopy.

Rapid LC–TOFMS Separation and Identification of Diarylheptanoids and Gingerol-Related Compounds in Dried Ginger

A tandem liquid chromatographic–time-of-flight mass spectrometric (LC–TOFMS) method has been developed for rapid separation and identification of diarylheptanoids and gingerol-related compounds in aqueous extracts of dried ginger. Total-ion-current chromatograms and mass spectra were acquired. A formula database of known compounds was established, against which components of dried ginger could be rapidly identified by matching their exact masses with theoretical masses of compounds calculated from their empirical formulae. Identification of 20 compounds was accomplished with error of 4 ppm, and further confirmation of elemental composition was obtained from the abundance of the isotope peaks. LC–TOFMS has been shown to be a useful tool for rapid identification of compounds in aqueous extracts of dried ginger.

Determination of Pesticide Residues in Fruit-Based Soft Drinks

Here we report the first worldwide reconnaissance study of the presence and occurrence of pesticides in fruit-based soft drinks. While there are strict regulations and exhaustive controls for pesticides in fruits, vegetables, and drinking water, scarce attention has been paid to highly consumed derivate products, which may contain these commodities as ingredients. In the case of the fruit-based soft drinks industry, there are no clear regulations, relating to pesticides, which address them, even when there is significant consumption in vulnerable groups such as children. In this work, we have developed a screening method to search automatically for up to 100 pesticides in fruit-based soft drinks extracts based on the application of liquid chromatography-electrospray time-of-flight mass spectrometry (LC-TOF MS). The sample extracts injected were obtained by a preliminary sample treatment step based on solid-phase extraction using hydrophilic-lipophilic balanced polymer-based reverse phase cartridges and methanol as eluting solvent. Subsequent identification, confirmation, and quantitation were carried out by LC-TOF MS analysis: the confirmation of the target species was based on retention time matching and accurate mass measurements of protonated molecules ([M + H]+) and fragment ions (obtaining accuracy errors typically lower than 2 ppm). With the proposed method, we measured over 100 fruit-based soft drink samples, purchased from 15 different countries from companies with brands distributed worldwide and found relatively large concentration levels of pesticides in most of the samples analyzed. The concentration levels detected were of the micrograms per liter level, low when considering the European maximum residue levels (MRLs) set for fruits but very high (i.e., 300 times) when considering the MRLs for drinking or bottled water. The detected pesticides (carbendazim, thiabendazole, imazalil and its main degradate, prochloraz and its main degradate, malathion, and iprodione) are mainly those applied to crops in the final stages of production (postharvest treatment), some of them contain chlorine atoms in their structures. Therefore, steps should be taken with the aim of removing any traces of pesticides in these products, in order to avoid this source of pesticide exposure on the consumer, particularly on vulnerable groups with higher exposure, such as children.