Characterization and determination of linear alkylbenzenesulfonates in environmental water samples by high-performance liquid chromatography with a hydrophilic polymer column and electrospray ionization mass spectrometric detection.

A liquid chromatography-mass spectrometry (LC/MS) method was developed for the separation and determination of linear alkylbenzenesulfonates (C10-C14 LAS) in environmental water samples using a hydrophilic polymer column (Shodex Mspak GF-310 4D). This method involves a solid-phase extraction of the LAS samples with a Sep-Pak PS-2 cartridge. The LAS components were separated on the column with a mobile phase of 29% (w/v) acetonitrile-water containing 0.8 mM di-n-butylammonium acetate and 0.2 M acetic acid, and were detected by mass spectrometry with electrospray ionization. Detection limits of the developed method based on selected ion monitoring (SIM) technique for the C10-C14 LAS standards were 13-47 ng L(-1). The concentrations of the C10-C14 LAS in the environmental water samples ranged between 5-317 microg L(-1) for a river water sample and 0.4-6.4 microg L(-1) for a seawater sample. Linear relationships between the logarithms of retention factors and the alkyl chain lengths for each phenyl positional isomer of LAS could successfully be used for the identification of the isomer peaks.     

Ion-trap tandem mass spectrometry for the determination of heterocyclic amines in food

Heterocyclic amines (HAs) are mutagenic compounds to which humans are regularly exposed through diet. Due to the high complexity of the sample matrix and the low level of concentration of HAs, sensitive and selective analytical methodologies are required. Here we describe a methodology based on liquid chromatography-atmospheric pressure chemical ionisation tandem mass spectrometry using an ion-trap to analyse HAs. The collision-induced dissociation parameters for tandem ion-trap spectrometric analysis of these mutagenic compounds were optimised, and the full scan MS-MS spectra were used for unequivocal identification of the analytes. For aminoimidazoazaarenes, the most abundant ions were derived from the loss of a methyl group and the breaking of the aminoimidazole moiety, while for carbolines the major product ions arose from the loss of ammonia and HCN. Moreover, the performance of the LC-atmospheric pressure chemical ionisation MS-MS method was evaluated. The good precision (RSD lower than 11%) and the low detection limits achieved (10-60 pg injected) allow the determination of HAs at low part-per-billion level (0.4-5.0 ng g(-1)) in a lyophilised meat extract.     

Determination of 1,4-benzodiazepines and their metabolites by capillary electrophoresis and high-performance liquid chromatography using ultraviolet and electrospray ionisation mass spectrometry.

A study is presented for the separation and determination of fifteen 1,4-benzodiazepine drugs and metabolites by capillary electrophoresis (CE) compared with high-performance liquid chromatography (HPLC). A comparison is made between the CE determination of the compounds by conventional UV detection and LC determination with electrospray ionisation (ESI) ion-trap mass spectrometry. CE is shown to provide superior separation to HPLC but the MS-MS capability of the ion-trap allows for the specific detection and determination of four of the compounds, diazepam, N'-desmethyldiazepam, oxazepam and temazepam in the hair of a patient under clinical treatment with diazepam and temazepam. Selected mixtures of drugs and metabolites are determined by CE and LC and the determination of diazepam and its metabolites by CE-UV-ESI-MS-MS is also presented.     

Determination of alkyl benzyl and dialkyl dimethyl quaternary ammonium biocides in occupational hygiene and environmental media by liquid chromatography with electrospray ionisation mass spectrometry and tandem mass spectrometry

A new method for the simultaneous qualitative and quantitative determination of alkyl benzyl and dialkyl quaternary ammonium compounds (QACs) has been developed. Analysis is by reversed-phase high-performance liquid chromatography coupled with electrospray ionisation mass spectrometry. QACs are extremely amenable to the electrospray ionisation technique (limit of detection of BAC C12 homologue 3 ng ml(-1)). The selectivity of mass spectrometric detection allows simultaneous determination of benzyl and dialkyl dimethyl ammonium compounds. The method was successfully applied to the analysis of real samples (occupational hygiene sampling devices, products and swimming pool water). Structural information was obtained by MS-MS and cone voltage ion dissociation techniques. Ion dissociation enabled the structural elucidation of an unknown quaternary ammonium compound present in a commercial formulation.     

Determination of non-ionic polyethoxylated surfactants in wastewater and river water by mixed hemimicelle extraction and liquid chromatography-ion trap mass spectrometry

The capability of hemimicelles-based solid phase extraction (SPE)/liquid chromatography/atmospheric pressure chemical ionisation in positive mode, ion trap mass spectrometry (LC/(APCl+-IT)-MS) for the concentration, separation and quantitation of non-ionic surfactants has been investigated. Concentration was based on the formation of mixed aggregates of analytes [alkylphenol ethoxylates (APE, octyl and nonyl) and alkyl ethoxylates (AE, C12-C16)] with the anionic surfactant sodium dodecyl sulphate (SDS) that is adsorbed on alumina. Parameters affecting SPE were investigated on the basis that hemimicelles are dynamic entities in equilibrium with the aqueous phase. The performance of ion trap mass spectrometry for MS and MS/MS quantitation of non-ionic homologues was assessed. Recoveries of analytes from wastewater influent and effluent and river water samples ranged between 91 and 98% and were found independent on the length of the alkyl chain under the optimised conditions. Anionic surfactants did not interfere to the levels found in environmental samples. The detection limits ranged between 14 and 111 ng/l for wastewater influent, 10 and 40 for wastewater effluent and 4 and 35 for river water, after concentration of 250, 500 and 750 ml of sample, respectively. The approach was applied to the determination of AE and APE in influent and effluent samples from four wastewater treatment plants and four river samples. The concentrations of individual non-ionic surfactants found ranged between 0.3 and 373 microg/l.     

Evaluation of quadrupole time-of-flight tandem mass spectrometry and ion-trap multiple-stage mass spectrometry for the differentiation of C-glycosidic flavonoid isomers

LC-MS-MS is becoming a very important tool for the on-line identification of natural products in crude plant extracts. For an efficient use of this technique in the dereplication of natural products, a careful study of the parameters used to generate informative MS-MS spectra is needed. In this paper, the collision-induced dissociation (CID) MS-MS spectra of ubiquitous C-glycosidic flavonoids have been systematically studied using hybrid quadrupole time-of-flight and ion-trap (IT) mass analysers under various CID energy conditions. Efficient differentiation of flavonoid C-glycoside isomers was possible, based on the comparison of CID-MS-MS spectra of particular C-glycoside unit fragments. Striking differences between 6-C and 8-C flavonoid glycosides were especially observed in the product ion spectra of their 0.2X+ fragments ([M+H-120]+). Some guidelines for the on-line characterisation of C-glycosidic flavonoids by LC-MS-MS or LC-multiple-stage MS are given.     

Liquid chromatography with electrospray ionisation mass spectrometric detection of phenolic compounds from Olea europaea.

The results demonstrate the potential of electrospray ionisation mass spectrometry for the specific detection of phenolic species in olives. Phenolic compounds were detected with greater sensitivity in the negative ion mode, but results from positive and negative ion modes were complementary with the positive ion mode showing structurally significant fragments. This is demonstrated by the identification of oleuropein and isomers of verbascoside. The structure of the latter were confirmed by retention, mass spectral and nuclear magnetic resonance data. These isomers have not previously been reported in olive.     

Determination of the strong mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and its analogues by GC-ITD-MS-MS

A new analytical method has been developed for the determination of chlorinated and brominated hydroxyfuranones. The method is based on separation by GC and selective determination of the compounds by use of an ion-trap mass detector. MS-MS fragmentation in an ion-trap detector can be regarded as an alternative to high-resolution mass spectrometry. Unique precursor ions were selected from the EI mass spectra and product-ion patterns were studied for a variety of collision energies. From these data, abundant mass transitions were selected for quantification and confirmation of compound identity. The method was applied to a spiked sample of chlorine-disinfected drinking water and it was found that the GC-MS-MS procedure is at least as sensitive and selective as previously published methods.     

Elucidation of diazinon metabolites in rice plants by liquid ‎chromatography ion-trap mass spectrometry

ABSTRACT

A fast, selective and sensitive reversed-phased liquid chromatography coupled to ion-trap mass spectrometry has been developed to elucidate and confirm the diazinon metabolites with a wide range of polarity in the rice plant samples. Sample extraction and purification were performed with a QuEChERS-based (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure. To boost all metabolism sensitivities, all rice extracts were concentrated under vacuum to near dryness and taken up into initial mobile phase. Careful optimisation of the LC–MS/MS parameters were achieved in order to attain a fast separation with the best sensitivity. The detection was carried out on an ion-trap mass spectrometer by electrospray ionisation in positive ion mode (ESI+) with multiple reaction monitoring.     

Separation and identification of ceramides in the human stratum corneum by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry and electrospray multiple-stage mass spectrometry profiling

Summary A sensitive, selective, and rapid method is described for analysis of ceramides in the human stratum coracum by direct coupling of HPLC with an electrospray ion-trap mass spectrometry. Nonaqueous reversed-phase chromatography stabilizes the electrospray ionization, resulting in sensitivity that enables direct measurement of skin lipid extracts with no special sample preparation. Assignment of individual signals to the corresponding ceramide species is based on interpretation of the fragment spectra from MS-MS experiments. This enables much finer differentiation between ceramdies than that achievable by thin-layer chromatography. Summary A sensitive, selective, and rapid method is described for analysis of ceramides in the human stratum corneum by direct coupling of HPLC with an electrospray ion-trap mass spectrometry. Nonaqueous reversed-phase chromatography stabilizes the electrospray ionization, resulting in sensitivity that enables direct measurement of skin lipid extracts with no special sample preparation. Assignment of individual signals to the corresponding ceramide species is based on interpretation of the fragment spectra from MS-MS experiments. This enables much finer differentiation between ceramides than that achievable by thin-layer chromatography.     

Analysis of linear alkylbenzenesulfonates in water samples by large-volume injection-port derivatization and gas chromatography-mass spectrometry.

This work presents a modified method to analyze linear alkylbenzenesulfonates (LASs) in water samples. The method involves extraction of samples by a graphitized carbon black (GCB) cartridge, and direct derivatization in the GC injection port using a large-volume (10-20 microl) direct sample introduction (DSI) device with tetraalkylammonium (TAA) salts. The analytes were then identified and quantitated by ion-trap GC-MS. The large-volume DSI injection-port derivatization technique provides sensitivity, fast and reproducible results for LAS residues, to quantitation at 0.1 microg/l in 200 ml of water samples. The retention effect of TAA salts in the injection port was not detected. Enhanced selected mass chromatograms of [M-55]+ ions of butylated C10-C13 LASs by electron impact ionization MS allows one to determine LAS residues at trace levels in environmental samples. Recovery of total LASs in spiked variety water samples ranged from 89 to 112% while RSDs ranged from 2 to 13%.     

Capillary electrophoresis-electrospray ion-trap mass spectrometry for the separation of chlorophenols

Eighteen positional isomers of chlorophenols were separated by capillary electrophoresis (CE) and detected on-line by electrospray ionization ion-trap mass spectrometry (MS). Conditions for the coupling of CE to MS, e.g., the concentration of carrier electrolyte, the sheath liquid composition and the sheath gas flow-rate were optimized. Diethylmalonic acid (5 mM) at pH 7.25 and isopropanol-250 mM dimethylamine (80:20) as sheath liquid were used. The activation parameters for ion-trap mass spectrometric analysis of chlorophenols were optimized. The mass spectra, obtained for all the analytes, revealed that the [M-H]- ion was the base peak for all chlorophenols. Moreover, conditions for CE-MS-MS detection were established and [M-H-HCl]- ions were detected.     

Mixed aggregate-based acid-induced cloud-point extraction and ion-trap liquid chromatography-mass spectrometry for the determination of cationic surfactants in sewage sludge

Alkyl ammonium surfactants were extracted and concentrated from sludge samples using the acid-induced cloud-point extraction (ACPE) technique. Reversed-phase liquid chromatography-electrospray ionization in positive ion mode ion-trap mass spectrometry was then used for the separation, quantitation and identification of single homologues of the cationic surfactants. Variables affecting the ACPE efficiency were optimized using a spiked activated sludge. Total method recoveries ranged from 91 to nearly 100%. Detection limits for cationics in the sludge were between 40 and 75 ng/g. The analysis of cationic surfactants in activated and dehydrated sludge collected from two different sewage treatment plants revealed the presence of dialkyldimethyl, alkylbenzyldimethyl and alkyltrimethyl ammonium in the concentration range from 0.1 to 34 mg/kg. Alkylpyridinium surfactants were not detected. The persistence of alkyl ammonium surfactants in sewage sludge after treatments applied at municipal sewage plants was confirmed.     

Rearrangements in the electron-impact induced fragmentation reactions of 5-alkylthio-1,3,4-thiadiazolyl-2-amines

The low resolution mass spectra of a number of homologous 5-alkylthio-1,3,4-thiadiazolyl-2-amines have been determined. With the methylthio compound the only significant loss from the molecular ion is the sulphydryl radical. As the homologous series is ascended this reaction becomes less important and is insignificant with the butylthio isomers. The ethylthio compound suffers extensive loss of ethylene and when the alkyl group contains three or more carbon atoms the main reaction is always loss of the olefin coresponding to the alkyl group.All of the n-alkylthio compounds showed in addition loss of methylthio radical from the molecular ion. A mechanism is proposed and comparisons made with alkyl phenyl thioethers and alkylthio substituted heterocycles.     

Capillary electrophoresis-mass spectrometry for the analysis of quaternary ammonium herbicides

Conditions for the simultaneous determination of the three herbicides paraquat, diquat and difenzoquat and the two plant growth regulators chlormequat and mepiquat by pressure-assisted capillary electrophoresis coupled to mass spectrometry (ion-trap) using electrospray as ionisation source have been established. A 200 mM formic acid-ammonium formate buffer solution at pH 3.0 with 50% of methanol was used as carrier electrolyte. Some capillary electrophoresis-mass spectrometry parameters such as sheath liquid and sheath gas flow-rates, sheath liquid composition, electrospray voltage andthe CE capillary position were optimised. The MS and MS-MS spectra of positive ions were studied in order to obtain structural information for the confirmation of the identity. The use of labelled standards allowed to confirm fragment ions assignation. The detection limits, based on a signal-to-noise ratio of 3:1, were between 0.5 and 2.5 mg l(-1) with hydrodynamic injection (10 s) and between 1 and 10 microg l(-1) with elecrokinetic injection (20 s, 10 kV) using standards in ultrapure water. Quality parameters such as linearity and run-to-run precision (n=6) were established. Quantitation was carried out using labelled standards. The method has been applied to the analysis of contaminated irrigation water and spiked mineral water samples.     

Assessment of the pollutant elimination efficiency by gas chromatography/mass spectrometry, liquid chromatography-mass spectrometry and -tandem mass spectrometry. Comparison of conventional and membrane-assisted biological wastewater treatment processes

The elimination efficiency of advanced conventional biological wastewater treatment was compared to membrane-assisted biological wastewater treatment. The sum parameter analyses dissolved organic carbon (DOC) and chemical oxygen demand (COD) or substance-specific analyses such as gas chromatography combined with mass spectrometry, flow injection analysis (FIA-MS) and liquid chromatography (LC-MS) in combination with mass or tandem mass spectrometry (MS-MS) were applied to assess elimination of hardly eliminable compounds in both types of wastewater treatment plants (WWTP). Reduction of DOC and COD in wastewater treatment processes confirmed a favourable elimination efficiency. Substance-specific methods which were applied in addition permitted a qualitative and semi-quantitative assessment of elimination with a visual pattern recognition approach. In order to identify pollutants either the NIST library of electron impact mass spectra for unpolar compounds or the laboratory-made collision-induced dissociation spectra library for polar pollutants was used. To assess elimination efficiency FIA-MS in the selected ion monitoring mode (SIM) besides high selective substance-specific mass spectrometric techniques such as parent ion scans and neutral loss scans were used for quantification. Results proved that membrane-assisted treatment was more effective than advanced biological treatment. In both types of WWTPs predominantly unpolar pollutants were eliminated, while all effluents were dominated by polar compounds of anthropogenic and biogenic origin. These unpolar and polar compounds which had been identified as hardly eliminable are reported about. Quantitative results obtained by FIA-MS, LC-MS and MS-MS for the elimination of alkyl polyglycol ethers, nonylphenol ethoxylates and linear alkylbenzenesulfonic acids from wastewater are presented.     

Determination of traces of five antifouling agents in water by gas chromatography with positive/negative chemical ionisation and tandem mass spectrometric detection.

A highly selective and sensitive gas chromatography-mass spectrometry methodology has been developed for the determination of five antifouling compounds, currently licensed for use in marine antifouling paints. The procedure uses an ion trap mass spectrometer provided with an external ion source that allows the combined use, in the same analysis, of positive (PCI) and negative (NCI) chemical ionisation and tandem mass spectrometric fragmentation (MS-MS). Ionisation and fragmentation processes were optimised individually for each compound, thus, permitting maximum sensitivity and selectivity to be obtained. A complete validation study, including those aspects that affect both correct quantification and unequivocal confirmation, demonstrated the good performance of the proposed method. Detection limits obtained were lower than 0.005 microg l(-1), except for Irgarol 1051 (0.050 microg l(-1)). The method was applied to real seawater samples from different     

Detection and characterization by mass spectrometry of radical adducts produced by linoleic acid oxidation

The formation of linoleic acid radical species under the oxidative conditions of the Fenton reaction (using hydrogen peroxide and Fe (II)) was monitored by FAB-MS and ES-MS using the spin trap 5,5-dimethyl-1-pyrrolidine-N-oxide, DMPO. Both the FAB and ES mass spectra were very similar and showed the presence of ions corresponding to carbon- and oxygen centered spin adducts (DMPO/L*, DMPO/LO*, and DMPO/LOO*). Cyclic structures, formed between the DMPO oxygen and the neighboring carbon of the fatty acid, were also observed. Electrospray tandem mass spectrometry of these ions was performed to confirm the proposed structure of these adducts. All MS/MS spectra showed an ion at m/z 114, correspondent to the [DMPO + H]+, and a fragment ion due to loss of DMPO (loss of 113 Da), confirming that they are DMPO adducts. ES-MS/MS spectra of alkoxyl radical adducts (DMPO/LO*) showed an additional ion at m/z 130 [DMPO - O + H]+, while ES MS/MS of peroxyl radical adducts (DMPO/LOO*) showed a fragment ion at m/z 146 [DMPO - OO + H]+, confirming both structures. Other fragment ions were observed, such as alkyl acylium radical ions, formed by cleavage of the alkyl chain after loss of water and the DMPO molecule. The identification of fragment ions observed in the MS/MS spectra of the different DMPO adducts suggests the occurrence of structural isomers containing the DMPO moiety both at C9 and C13. The use of ES tandem mass spectrometry, associated with spin trapping experiments, has been shown to be a valuable tool for the structural characterization of carbon and oxygen-centered spin adducts of lipid radicals.     

Separation of homologues and isomers of linear alkylbenzenesulfonates by capillary electrophoresis with sodium dodecyl sulfate,carboxylic acids and bile salts

The ability of several anionic compounds, including carboxylic and dicarboxylic acids, sodium dodecyl sulfate (SDS), and sodium deoxycholate (SDC) and other bile salts, to separate the C(10)-C(13) homologues and the corresponding 20 positional isomers of linear alkylbenzenesulfonates (LAS) by capillary electrophoresis was studied. Up to 19 peaks and a shoulder were observed with a background electrolyte (BGE) containing 10 mM phosphate (pH 6.8), 30% acetonitrile and 40 mM SDS, and 18 peaks were obtained with a BGE containing 10 mM borate (pH 9), 40% ethanol and 40 mM palmitic acid (PA). Resolution increased with the alkyl chain length of the carboxylic acid. Dicarboxylic acids with a short alkyl chain, as azelaic acid, were useful to separate the homologues without distinguishing between the isomers. Up to 16 peaks and a shoulder were distinguished with SDC. Resolution decreased with the other bile salts. The 6-C(11)/5-C(11) isomer pair was better resolved with SDC than with SDS, and the 2-C(12) isomer was isolated using both PA and SDC, but not with SDS. Only the 7-C(13)/6-C(13) pair could not be resolved with any of the discriminating agents used.     

Liquid chromatography with electrospray ion-trap mass spectrometry for the determination of yessotoxins in shellfish

Yessotoxins are a group of large polyether toxins, produced by marine dinoflagellates, which cause widespread contamination of filter-feeding shellfish. A new, sensitive liquid chromatography-mass spectrometry (LC-MS) method has been developed for the determination of yessotoxin (YTX) and 45-hydroxy-yessotoxin (45-OHYTX), a major metabolite in shellfish. The LC system was coupled, via an electrospray ionisation (ESI) source, to an ion-trap MS in negative mode. The molecular related ion species at m/z 1141 [M-2Na+H]- was used as the parent ion for multiple MS experiments. MS-MS and MS3 gave major fragment ions at m/z 1061 [1141-SO3H]- and m/z 945 [1061-C9H12O]-. Predominant ions, that are due to the fragmentation of the backbone structure of YTXs, were observed at the MS4 stage. Reversed-phase LC using a C16 amide column was preferable to C18 phases for the separation of YTX and 45-OHYTX. Optimum calibration and reproducibility data were obtained for YTX using LC-MS-MS; r 2=0.9960, RSD < or = 6.3% at 0.25 microg YTX/g (n=5). The detection limit (S/N=3) was 30 pg YTX on-column which corresponded to 3 ng/g shellfish tissue.