The European Reach legislation will possibly drive producers to develop newly designed chemicals that will be less persistent, bioaccumulative or toxic. If this innovation leads to an increased use ...of more hydrophilic chemicals it may result in higher mobilities of chemicals in the aqueous environment. As a result, the drinking water companies may face stronger demands on removal processes as the hydrophilic compounds inherently are more difficult to remove. Monitoring efforts will also experience a shift in focus to more water-soluble compounds. Screening source waters on the presence of (emerging) contaminants is an essential step in the control of the water cycle from source to tap water. In this article, some of our experiences are presented with the hybrid linear ion trap (LTQ) FT Orbitrap mass spectrometer, in the area of chemical water analysis. A two-pronged strategy in mass spectrometric research was employed: (i) exploring effluent, surface, ground- and drinking-water samples searching for accurate masses corresponding to target compounds (and their product ions) known from,
e.g. priority lists or the scientific literature and (ii) full-scan screening of water samples in search of ‘unknown’ or unexpected masses, followed by MS
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experiments to elucidate the structure of the unknowns. Applications of both approaches to emerging water contaminants are presented and discussed. Results are presented for target analysis search for pharmaceuticals, benzotriazoles, illicit drugs and for the identification of unknown compounds in a groundwater sample and in a polar extract of a landfill soil sample (a toxicity identification evaluation bioassay sample). The applications of accurate mass screening and identification described in this article demonstrate that the LC–LTQ FT Orbitrap MS is well equipped to meet the challenges posed by newly emerging polar contaminants.
Various buffers (ammonium acetate, ammonium formate, and ammonium hydrogencarbonate), acids (formic acid, acetic acid, heptafluorobutyric acid, and trifluoroacetic acid), and bases (ammonium ...hydroxide and morpholine) covering the range from 2 to 11.5 have been investigated for their performance in the separation of proteins by reversed-phase liquid chromatography (RPLC) and in their detection by electrospray mass spectrometry (ESI-MS). These additives were first tested for the detection of standard proteins by ESI-MS by flow-injection analysis (FIA). Those additives yielding the highest signals were employed for the separation of standard proteins by using three different reversed-phase columns: two C
18 columns (4.6 mm I.D. and 2.1 mm I.D.) and one perfusion column (2 mm I.D.). The sensitivity of the LC–MS system was evaluated with the column giving the best results and with those LC eluents enabling the LC separation of the proteins and also yielding the highest MS signals. For that purpose, calibration curves were compared for both LC–MS and FIA–MS. Formic acid was the additive yielding the highest responses in FIA–MS and trifluoroacetic acid (TFA) gave the best separation and recovery of the proteins. However, problems related to poor recovery of the proteins in the column when formic acid was used and the significant signal suppression observed in MS when TFA was employed, made neither of them suitable for the sensitive detection of the proteins in LC–MS.
Several water companies in the Netherlands use a combination of specifically targeted compound analysis (HPLC-UV and GC-MS) and effect monitoring (continuous biotests) to monitor source water quality ...and to screen for unknown compounds. In spring 2004, the Daphnia biomonitor at Keizersveer monitoring station alongside the River Meuse recorded several alarms. In this study, the combination of HPLC-DAD and Q-TOF MS techniques was used to identify the so-far unknown microcontaminant related to this Daphnia alarm as 3-cyclohexyl-1,1-dimethylurea. The maximum concentration of this compound in the River Meuse at the time of the alarm was estimated to be 5 μg/L. The response of the waterfleas to this compound was confirmed with a short-term and a long-term verification test. The origin of the pollutant is still unknown. This paper shows that the combined application of on-line continuous biotests and advanced chemical analysis is an effective tool for the detection and identification of unknown, potentially hazardous compounds for surface water quality monitoring. Biological effect monitoring and specific compound analysis complement each other and together provide the best possible insight in rapid surface water quality changes.
Direct injection of a large volume (900 μl) of a sample extract onto a liquid chromatographic (LC) column, LC separation and electrospray tandem mass spectrometric detection were used for the ...quantitative analysis of a wide polarity range of pesticides in carrots and potatoes. Rapid sample preparation involved extraction of a small amount of sample (2 g) with a small volume of organic solvent (3 ml), clean-up over a filter and dilution of the organic extract with the aqueous LC eluent. The extraction efficiency for the selected pesticides was studied using methanol, acetone and acetonitrile as solvents. Evaluation of the performance of the overall method, using extraction with acetonitrile and detection in the selected-reaction-monitoring mode, showed excellent linearity in the range of 2–100 μg/kg with limits of detection of 0.5–2 μg/kg for both types of vegetable. With relative standard deviations of the MS peak area measurements of less than 6.5% (
n=8) the repeatability of the method was fully satisfactory.
Repeated exposure to drugs of abuse causes persistent behavioural sensitization and associated adaptations in striatal neurotransmission, which is thought to play an important role in certain aspects ...of drug addiction. Remarkably, even a single exposure to psychostimulant drugs such as amphetamine or cocaine can be sufficient to elicit long‐lasting sensitization. The present study was designed to evaluate whether long‐lasting behavioural and neurochemical sensitization can also be evoked by a single exposure to morphine, an opiate drug of abuse. Rats were pretreated once with morphine (2, 10 or 30 mg/kg). Three weeks later, the locomotor effects of morphine and amphetamine, as well as the electrically evoked release of 3Hdopamine and 14Cacetylcholine from slices of nucleus accumbens and caudate–putamen, was assessed. In morphine‐pretreated rats, the psychomotor effects of morphine and amphetamine were sensitized. In addition, the electrically evoked release of 3Hdopamine and 14Cacetylcholine was augmented in slices of nucleus accumbens and caudate–putamen from morphine‐pretreated animals. Although the sensitization of the locomotor effect of morphine was less profound than previously observed after repeated intermittent morphine treatment, the enduring behavioural and neurochemical consequences of a single and repeated intermittent morphine treatment appear to be highly comparable. We therefore conclude that a single exposure to morphine induces long‐lasting behavioural sensitization and associated neuroadaptations.
A method is developed for the determination of polar pesticides and their transformation products atrazine, deethylatrazine, deisopropylatrazine, hydroxyatrazine, diuron, ...3,4-dichlorophenylmethylurea, 3,4-dichlorophenylurea (DPU), monuron, bentazone, anthranil-isopropylamide, chloridazon, metolachlor in surface, estuarine and sea water samples at the low ng/l level. Solid-phase extraction is combined off-line with column liquid chromatography–electrospray ionization tandem mass spectrometric detection (LC–ESI-MS–MS). The applicability of two solid-phase materials, i.e., LiChrolut EN cartridges and graphitized carbon black extraction disks, is evaluated. The influence of the organic solvent used in gradient LC, as well as the amount of co-extracted humic material on the ESI process is studied. The eluotropic strength of the organic solvent was found to have a distinct effect on the sensitivity of ESI-MS if coupled with LC gradient separations. Methanol gave much better results than acetonitrile and phenylurea compounds are more susceptible to solvent changes than triazines. Co-extracted humic material causes signal suppression in ESI-MS–MS detection. The degree of suppression depends upon the sample pH and the nature of the samples, i.e., surface or estuarine water. Detection limits in LC–ESI-MS–MS ranged from 0.2 to 2 ng/l, with the exception of DPU (8 ng/l). The applicability of the procedure was demonstrated by analyzing surface and estuarine water.
The ability to rapidly identify active compounds in a complex mixture (e.g., natural products extract) is still one of the major problems in natural products screening programs. An elegant way to ...overcome this problem is to separate the complex mixture by gradient liquid chromatography followed by online biochemical detection parallel with chemical characterization, referred to as high-resolution screening (HRS). To find and identify phosphodiesterase (PDE) inhibitors in natural products extracts using the HRS technology, the authors developed a continuous-flow PDE enzymatic assay. The suitability of the continuous-flow PDE enzymatic assay for natural products screening was demonstrated. After optimization of the continuous-flow PDE assay, the limit of detection for 3-isobutyl-1-methyl-xanthine (IBMX) was 1 muM, with a dynamic range from 1 to 100 muM IBMX. The applicability of the HRS technology for the detection of PDE inhibitors in natural products extracts was demonstrated by the analysis of a plant extract spiked with 2 naturally occurring PDE inhibitors. The plant extract was analyzed with 2 assay lines in parallel, enabling background fluorescence correction of the sample. The simultaneous quantification of the active compounds using evaporative light-scattering detection allowed the estimation of the IC(50) value of the active compounds directly in the crude extract.
Dual-pre-column-based trace enrichment combined on-line with liquid chromatography–diode-array UV and tandem mass spectrometric detection was used to determine a wide polarity range of organic ...microcontaminants in river water. Various sorbents were studied for their extraction efficiency of (highly) polar and acidic compounds and their ability to selectively remove humic substances, which are normally co-extracted and interfere in the UV detection of polar microcontaminants. An optimised on-line dual-pre-column set-up with PLRP-S in the first pre-column and Hysphere-1 in the second pre-column was used to study the analytical performance of the procedure. Tandem MS was used for confirmation purposes and to quantify the organic microcontaminants in river water at the low-ng/l level. In addition, the influence of the type of sample (drinking and river water) on suppression of analyte responses in electrospray ionization MS was studied.
The applicability of a homogeneous on-line continuous-flow, multi-protein biochemical assay was demonstrated for the interaction between fluorescein−biotin and streptavidin and for digoxin and ...anti-digoxigenin using electrospray quadrupole time-of-flight mass spectrometry (Q-TOF MS). In the on-line continuous-flow biochemical MS-based system several receptors (e.g., streptavidin and anti-digoxigenin, respectively) were allowed to react with corresponding reporter ligands (e.g.,fluorescein−biotin and digoxin, respectively). The methodology presented allows the simultaneous measurement of affinity and molecular mass of an active compound. By using automated MS and MS−MS switching functions of the Q-TOF, structure information is obtained allowing the characterization of bioactive compounds. No cross-reactivities were observed between the two model systems fluorescein−biotin/streptavidin and digoxin/anti-digoxigenin.
The applicability of trace enrichment and separation of microcontaminants on a 10 mm×2 mm I.D. high-pressure packed (8 μm C18 bonded silica or 10–15 μm PLRP-S) column combined on-line with an ...atmospheric pressure chemical ionization MS–MS system is demonstrated for the target analysis of herbicides in river water. Tailor-made procedures are obtained for a limited number of analytes by tuning the chromatographic efficiency of the short LC column and the specificity of tandem MS, in order to minimize the analysis time. With the on-line short-column LC–MS–MS method, good linearity is obtained for the herbicides in the range of 0.1–10 μg/l. The relative standard deviations of peak areas are less than 5% and, with only 4-ml samples, detection limits of 0.01–0.1 μg/l can be achieved. The total analysis time is 10–15 min. The 10 mm×2 mm I.D. LC columns packed with 8 μm particles show good stability and can be used for at least 40 analyses. Target compound analyses of river water allowed the confirmation of the presence of herbicides such as diuron, simazine, atrazine and terbutylazine at sub-μg/l levels.
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