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Concept: Liquid chromatography-mass spectrometry

161

Despite recent advances in understanding mechanism of toxicity, the development of biomarkers (biochemicals that vary significantly with exposure to chemicals) for pesticides and environmental contaminants exposure is still a challenging task. Carbofuran is one of the most commonly used pesticides in agriculture and said to be most toxic carbamate pesticide. It is necessary to identify the biochemicals that can vary significantly after carbofuran exposure on earthworms which will help to assess the soil ecotoxicity. Initially, we have optimized the extraction conditions which are suitable for high-throughput gas chromatography mass spectrometry (GC-MS) based metabolomics for the tissue of earthworm, Metaphire posthuma. Upon evaluation of five different extraction solvent systems, 80% methanol was found to have good extraction efficiency based on the yields of metabolites, multivariate analysis, total number of peaks and reproducibility of metabolites. Later the toxicity evaluation was performed to characterize the tissue specific metabolomic perturbation of earthworm, Metaphire posthuma after exposure to carbofuran at three different concentration levels (0.15, 0.3 and 0.6 mg/kg of soil). Seventeen metabolites, contributing to the best classification performance of highest dose dependent carbofuran exposed earthworms from healthy controls were identified. This study suggests that GC-MS based metabolomic approach was precise and sensitive to measure the earthworm responses to carbofuran exposure in soil, and can be used as a promising tool for environmental eco-toxicological studies.

Concepts: Metabolism, Toxicology, Chromatography, Liquid chromatography-mass spectrometry, Metabolomics, Earthworm, Gas chromatography-mass spectrometry

84

Urine has long been a “favored” biofluid among metabolomics researchers. It is sterile, easy-to-obtain in large volumes, largely free from interfering proteins or lipids and chemically complex. However, this chemical complexity has also made urine a particularly difficult substrate to fully understand. As a biological waste material, urine typically contains metabolic breakdown products from a wide range of foods, drinks, drugs, environmental contaminants, endogenous waste metabolites and bacterial by-products. Many of these compounds are poorly characterized and poorly understood. In an effort to improve our understanding of this biofluid we have undertaken a comprehensive, quantitative, metabolome-wide characterization of human urine. This involved both computer-aided literature mining and comprehensive, quantitative experimental assessment/validation. The experimental portion employed NMR spectroscopy, gas chromatography mass spectrometry (GC-MS), direct flow injection mass spectrometry (DFI/LC-MS/MS), inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) experiments performed on multiple human urine samples. This multi-platform metabolomic analysis allowed us to identify 445 and quantify 378 unique urine metabolites or metabolite species. The different analytical platforms were able to identify (quantify) a total of: 209 (209) by NMR, 179 (85) by GC-MS, 127 (127) by DFI/LC-MS/MS, 40 (40) by ICP-MS and 10 (10) by HPLC. Our use of multiple metabolomics platforms and technologies allowed us to identify several previously unknown urine metabolites and to substantially enhance the level of metabolome coverage. It also allowed us to critically assess the relative strengths and weaknesses of different platforms or technologies. The literature review led to the identification and annotation of another 2206 urinary compounds and was used to help guide the subsequent experimental studies. An online database containing the complete set of 2651 confirmed human urine metabolite species, their structures (3079 in total), concentrations, related literature references and links to their known disease associations are freely available at http://www.urinemetabolome.ca.

Concepts: Metabolism, Chromatography, High performance liquid chromatography, Analytical chemistry, Metabolite, Liquid chromatography-mass spectrometry, Metabolomics, Metabolome

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A highly sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the determination of limonin in beagle dog plasma using nimodipine as internal standard. The analyte and internal standard (IS) were extracted with ether followed by a rapid isocratic elution with 10 mm ammonium acetate buffer-methanol (26:74, v/v) on a C column (150 × 2.1 mm i.d.) and subsequent analysis by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 469.4 → 229.3 and m/z 417.2 → 122.0 were used to measure the analyte and the IS. The assay was linear over the concentration range of 0.625-100 ng/mL for limonin in dog plasma. The lower limit of quantification was 0.312 ng/mL and the extraction recovery was >90.4% for limonin. The inter- and intra-day precision of the method at three concentrations was less than 9.9%. The method was successfully applied to pharmacokinetic study of limonin in dogs. Copyright © 2012 John Wiley & Sons, Ltd.

Concepts: Ammonia, Mass spectrometry, Calculus, Analytical chemistry, Liquid chromatography-mass spectrometry, Titration

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The release of pharmaceuticals in the environment, as parent compounds, metabolites and transformation products, and the consequent risks posed to living organisms due to the unintended exposure of the latter to these chemicals are nowadays of increasing scientific concern. The development of advanced oxidation processes able to degrade these substances is in the core of the current research objectives, the main target being the removal of these compounds from wastewaters. Often the focus is on the removal of the parent compound only. However, these processes can form transformation products. Knowledge on the risk related to such transformation products is scarce. Among others, knowledge on their toxic effects and their biodegradability is of importance not only when they are present in the environment but also for the assessment of the advanced oxidation processes' efficiency applied for their degradation. Photolytic (UV irradiation) and photocatalytic treatment (UV irradiation in the presence of TiO(2)) of the fluoroquinolone ofloxacin were applied, and the biodegradability of the formed products was investigated using the Closed Bottle test (OECD 301 D). Various transformation products, formed both during the photo(cata)lytic treatment and the Closed Bottle test, were identified using chromatographic analysis with an ultra high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) system. The transformation products formed during the phototreatments were found to be non-readily biodegradable as the biodegradation percentages were close to zero. The persistence of the various photo(cata)lytic transformation products during the Closed Bottle test may be attributed to the fluorine present in all the transformation products formed. The transformation products identified suggest that two transformation routes were present: decarboxylation and opening of the piperazinyl ring. Interestingly, it was observed that in the presence of a readily biodegradable carbon source (sodium acetate), the biodegradation percentage increased drastically for some of the photolytically treated samples. This was not the case for the photocatalytically treated samples, in which also mineralization of the parent compound was achieved faster. Further research is needed, however, in order to increase the understanding of the conditions that may lead to less potent and persistent substances during the application of such engineered or natural processes.

Concepts: Chromatography, Biodegradation, Liquid chromatography-mass spectrometry, Bioremediation, Microbial biodegradation, Biodegradability prediction

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Fesoterodine is a non-selective muscarinic-receptor antagonist, used in the treatment of overactive bladder syndrome. A highly sensitive, selective and rapid method has been developed for the simultaneous determination of fesoterodine and its active metabolite, 5-hydroxymethyl tolterodine (5-HMT) in human plasma by liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS). Due to rapid conversion of parent drug to 5-HMT, ex vivo stability of fesoterodine in human plasma was extensively studied to optimize the extraction protocol. The analytes and their deuterated analogs were quantitatively extracted from 100μL human plasma by liquid-liquid extraction in methyl tert-butyl ether: n-hexane. The chromatographic separation of analytes was achieved on a Kromasil C18 (100mm×4.6mm, 5μm) column under isocratic conditions. The method was validated over a dynamic concentration range of 0.01-10ng/mL for both the analytes. Ion-suppression effects were investigated by post-column infusion of analytes. The precision (% CV) values for the calculated slopes of calibration curves, which would reflect the relative matrix effect, were less than 1.5% for both the analytes. The intra-batch and inter-batch precision (% CV) across quality control levels varied from 1.82 to 3.73% and the mean extraction recovery was >96% for both the analytes. The method was successfully applied to a bioequivalence study of 8mg fesoterodine tablet formulation (test and reference) in 12 healthy Indian subjects under fasted and fed condition. The assay reproducibility estimated by reanalysis of incurred samples showed a change of ±12.0%.

Concepts: Scientific method, Mass spectrometry, Urology, Sociology, Chromatography, Overactive bladder, Liquid chromatography-mass spectrometry, Bioequivalence

28

This study aims to measure the serum level of 25-hydroxyvitamin D(3) (25-OH-D(3)) in 302 patients with rheumatoid arthritis (RA), studying the association to disease activity. Three hundred two RA patients underwent clinical examination and serological analysis. 25-Hydroxyvitamin D(3) was determined by high-performance liquid chromatography-tandem mass spectrometry. Vitamin D(3) deficiency defined as serum levels of 25-hydroxyvitamin D(3) below 50 nmol/l was detected in 101 RA patients (33.4 %). There was no significant correlation between the serum level of 25-hydroxyvitamin D(3) and Disease Activity Score 28 (DAS28) (3w) score. In a subpopulation of RA patients with very low serum level of 25-OH-D(3) (≤15 nmol/l) (n = 15), there were significant differences compared to patients with normal 25-OH-D(3) (n = 200): higher percentage of patients with positive rheumatoid factor (100.0 versus 77.5 %; p = 0.05), higher CRP (28.7 versus 14.8 mg/l; p = 0.001), higher number of patients treated with at least three disease-modifying antirheumatic drugs (DMARDs) (40.0 versus 14.5 %; p = 0.02), higher number of patients with high disease activity DAS28 score of ≥5.1 (20.0 versus 4.5 %; p = 0.01), lower age (54.5 versus 64.0 years; p = 0.003) and shorter disease duration (5.1 versus 10.3 years; p = 0.06). Deficiency of 25-hydroxyvitamin D(3) was detected in 33.4 % of the RA patients. A subpopulation of patients with severe deficiency of vitamin D(3) serum level of ≤15 nmol/l was characterised by all being positive for rheumatoid factor, high percentage of patients with very high disease activity and high percentage of patients treated with at least three DMARDs.

Concepts: Immunology, Rheumatoid arthritis, Rheumatology, Arthritis, Liquid chromatography-mass spectrometry, Disease-modifying antirheumatic drug, Hydroxychloroquine, Rheumatoid factor

28

For the first time, a carboxyl group derivatization assay has been developed and validated for the determination of the cholesterol-lowering drug rosuvastatin in human serum at picogram level by high-performance liquid chromatography with fluorescence detection. The assay procedure involved a simple one-step liquid-liquid extraction of rosuvastatin with lovastatin as internal standard from serum with an ethyl acetate-methyl tertiary buthyl ether (1:1) mixture. After pre-column derivatization with 9-anthryldiazomethane at room temperature for one hour, the reaction mixture was injected onto a Phenomenex, Synergi C18 column (250 × 4.6 mm, 4 µ i.d.). The analytes were separated with a mobile phase composed of acetonitrile-water in gradient elution mode and detected at λ(em) = 410 nm, exciting at 366 nm. Calibration curves were constructed in concentration range of 0.01-20.0 ng/mL and limit of detection and limit of quantification values were found to be 0.68 and 2.30 pg/mL, respectively. To test suitability of the developed methods for clinic use, the pharmacokinetics of rosuvastatin were investigated after oral administration of a 20 mg rosuvastatin film tablet to a healthy volunteer and maximum plasma concentration, time to reach that concentration and elimination half life were found to be 17.5 ng/mL, 3.5 h and 18.09 h, respectively.

Concepts: Alcohol, Functional group, Chromatography, High performance liquid chromatography, Analytical chemistry, Gas chromatography, Liquid chromatography-mass spectrometry, Phenomenex

28

An LC-MS/MS method developed for simultaneous analysis of 54 veterinary drug residues of six families in pork meat samples, including sulfanilamide, nitroimidazoles, quinolones, macrolide antibiotics, lincosamides, and praziquantel. The pork meat sample was prepared by extraction with ACN, and clean-up on a C(18) SPE cartridge. The sample was separated on a C(8) column and eluted with ACN, methanol, and formic acid. The MS/MS detector is operated in the multiple reaction monitoring mode, acquiring two specific precursor-product ion transitions per target compound. The method showed excellent linearity (R(2) ≥ 0.99) and high precision (relative SD, RSD ≤ 19.8%) for all compounds. The method quantification limits of 54 veterinary drug residues were in the range of 0.3-3.0 μg/kg. Recoveries for most analytes based on matrix-matched calibration in matrices were 20.9-121.0%. This method has been successfully applied for analysis of more than 100 pork meat samples from the local market; five of the 54 drugs were detected.

Concepts: Mass spectrometry, Acetic acid, Solvent, Liquid chromatography-mass spectrometry, Pork, Methanol, Formic acid, Formaldehyde

28

A sensitive and robust method using solid-phase extraction and ultrasonic extraction for preconcentration followed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS-MS) has been developed for determination of 19 biocides: eight azole fungicides (climbazole, clotrimazole, ketoconazole, miconazole, fluconazole, itraconazole, thiabendazole, and carbendazim), two insect repellents (N,N-diethyl-3-methylbenzamide (DEET), and icaridin (also known as picaridin)), three isothiazolinone antifouling agents (1,2-benzisothiazolinone (BIT), 2-n-octyl-4-isothiazolinone (OIT), and 4,5-dichloro-2-n-octyl-isothiazolinone (DCOIT)), four paraben preservatives (methylparaben, ethylparaben, propylparaben, and butylparaben), and two disinfectants (triclosan and triclocarban) in surface water, wastewater, sediment, sludge, and soil. Recovery of the target compounds from surface water, influent, effluent, sediment, sludge, and soil was mostly in the range 70-120 %, with corresponding method quantification limits ranging from 0.01 to 0.31 ng L(-1), 0.07 to 7.48 ng L(-1), 0.01 to 3.90 ng L(-1), 0.01 to 0.45 ng g(-1), 0.01 to 6.37 ng g(-1), and 0.01 to 0.73 ng g(-1), respectively. Carbendazim, climbazole, clotrimazole, methylparaben, miconazole, triclocarban, and triclosan were detected at low ng L(-1) (or ng g(-1)) levels in surface water, sediment, and sludge-amended soil. Fifteen target compounds were found in influent samples, at concentrations ranging between 0.4 (thiabendazole) and 372 ng L(-1) (methylparaben). Fifteen target compounds were found in effluent samples, at concentrations ranging between 0.4 (thiabendazole) and 114 ng L(-1) (carbendazim). Ten target compounds were found in dewatered sludge samples, at concentrations ranging between 1.1 (DEET) and 887 ng g(-1) (triclocarban).

Concepts: Water, Liquid chromatography-mass spectrometry, Insect repellent, Paraben, Butylparaben, DEET, Icaridin, Ethylparaben

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Combination techniques such as gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) are commonly used for pesticide residue analysis, but there is no reported method for the simultaneous analysis of multiple pesticides in a sample using a single instrument. Supercritical fluid chromatography (SFC) offers high resolution at high flow rates and various separation modes and hence may aid the rapid simultaneous analysis of pesticide. We developed an SFC/MS/MS method and analyzed 17 pesticides with a wide range of polarities (logP(ow)=-4.6 to 7.05) and molecular weights (112.1-888.6) within 11min using a polar-embedded reversed-phase column. To the best of our knowledge, there is no previous report on the SFC analysis of a wide variety of compounds, including highly hydrophilic ones. By SFC, diquat dibromide (logP(ow)=-4.6), together with cypermethrin (logP(ow)=6.6) and tralomethrin (logP(ow)=5.05), could be detected in the presence of various other pesticides using a single mobile phase. SFC/MS allows for the rapid and simultaneous analysis of low concentrations (ng/L levels) of pesticides that typically need to be analyzed by GC/MS and LC/MS separately.

Concepts: Mass spectrometry, Chromatography, Analytical chemistry, Pesticide, Liquid chromatography-mass spectrometry, Supercritical fluid, Insecticide, Phase diagram