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Liquid Chromatography Tandem Mass Spectrometry (liquid + chromatography_tandem_mass_spectrometry)

Distribution by Scientific Domains
Chemistry75%
Medical Sciences12%
Life Sciences12%

Terms modified by Liquid Chromatography Tandem Mass Spectrometry

  • liquid chromatography tandem mass spectrometry method
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    Selected Abstracts

    Comparative oxidative metabolic profiles of clomipramine in cats, rats and dogs: preliminary results from an in vitro study

    JOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 5 2007
    C. LAINESSE
    The objectives of this in vitro study were to describe cytochrome-dependent metabolism of clomipramine in canine and feline microsomes, compare metabolic profiles between cats, rats and dogs, and investigate a potential gender-related difference in metabolic activity between male and female cats. Pooled liver microsomes were incubated with clomipramine, where species and gender-specific reactions were initiated by the addition of a nicotinamide adenine dinucleotide phosphate regenerating system and quenched with methanol at 0, 5, 15, 30, 45 and 60 min, and 0, 30, 60, 90, 120, 180, 240 and 360 min respectively. Liquid chromatography tandem mass spectrometry was used to measure clomipramine and its metabolites. Preliminary results showed that cat microsomes biotransformed clomipramine slower and less efficiently than rat and dog microsomes. Moreover, gender differences in metabolic profiles suggested that male cat microsomes may be less efficient demethylators and hydroxylators than female cat microsomes. As gender metabolic differences may carry clinical significance for this antidepressant, further studies are warranted. [source]

    Dissipation kinetics and mobility of chlortetracycline, tylosin, and monensin in an agricultural soil in Northumberland County, Ontario, Canada

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2006
    Jules C. Carlson
    Abstract A robust high-throughput method was refined to extract three growth-promoting antibiotics, tylosin (TYL), chlortetracycline (CTC), and monensin (MON), from soil. Analysis was performed by electrospray liquid chromatography tandem mass spectrometry. Soil dissipation rate studies were performed in a farm field soil for antibiotics applied with and without manure. Tylosin, CTC, and MON followed first-order dissipation kinetics with half-lives of 4.5, 24, and 3.3 d, respectively, with the addition of manure and 6.1, 21, and 3.8 d, respectively, without manure. Manure application significantly increased TYL dissipation rate, perhaps because of the introduced microbial flora, but had no significant effect on CTC or MON. Monensin dissipation half-life was found to be much shorter in the field study than in a controlled laboratory study, perhaps because of differences in microbial communities. The antimicrobials were not highly mobile. Chlortetracycline was the only antibiotic detected at 25 to 35 cm depth and only up to 2% of the initial concentration in a sandy loam soil. These antibiotics are therefore expected to degrade primarily in agricultural soils before moving to greater depths or to groundwater in significant concentrations in most agricultural systems. [source]

    Detection of Acute Diazepam Exposure in Bone and Marrow: Influence of Tissue Type and the Dose-Death Interval on Sensitivity of Detection by ELISA with Liquid Chromatography Tandem Mass Spectrometry Confirmation,

    JOURNAL OF FORENSIC SCIENCES, Issue 3 2009
    D.A.B.F.T., James H. Watterson Ph.D.
    Abstract:, Enzyme-linked immunosorbent assay (ELISA) and liquid chromatography tandem mass spectrometry (LC/MS/MS) were used to detect diazepam exposure in skeletal tissues of rats (n = 15) given diazepam acutely (20 mg/kg, i.p.), and killed at various times postdose. Marrow, epiphyseal, and diaphyseal bone were isolated from extracted femora. Bone was cleaned, ground, and incubated in methanol. Marrow underwent ultrasonic homogenization. Extracts and homogenates were diluted in phosphate buffer, and then underwent solid-phase extraction and ELISA. Relative sensitivity of detection was examined in terms of relative decrease in absorbance (ELISA) and binary classification sensitivity (ELISA and LC/MS/MS). Overall, the data showed differences in relative sensitivity of detection of diazepam exposure in different tissue types (marrow > epiphyseal bone > diaphyseal bone), which is suggestive of heterogenous distribution in these tissues, and a decreasing sensitivity with increasing dose-death interval. Thus, the tissue type sampled and dose-death interval may contribute to the probability of detection of diazepam exposure in skeletal tissues. [source]

    Determination of BAPTA-AM, the acetoxymethyl tetraester of BAPTA, in rat plasma by liquid chromatography tandem mass spectrometry

    JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2006
    Feng Zheng
    Abstract BAPTA-AM is the acetoxymethylester of the calcium chelator BAPTA and has demonstrated efficacy in several animal models of cerebral ischemia. This paper describes the development of a method for the determination of BAPTA-AM in rat plasma by liquid chromatography/tandem mass spectrometry. Owing to multiple ester groups in the structure of BAPTA-AM, [M + Na]+ was chosen as the analytical ion for quantification of BAPTA-AM. During the analytical method development, a high percentage of organic solvent and the addition of an amount of sodium acetate and formic acid in the mobile phase were found to favor the sensitivity and reproducibility of [M + Na]+. Poor fragmentation was usually observed in the MS/MS spectra of sodium adduct ions. However, abundant and reproducible fragment ions were observed for the BAPTA-AM sodium adduct ion, and therefore the traditional selective reaction-monitoring mode was used to further improve the sensitivity of MS detection. Because of the lability of the ester bond, a combination of fluoride and hydrochloric acid was applied to minimize the enzymatic hydrolysis, and acetonitrile was chosen to avoid the chemical hydrolysis or solvolysis during the sample collection and preparation procedure. On the basis of these studies, a rapid, sensitive and reproducible method for the determination of BAPTA-AM in rat plasma, using LC/ESI-MS/MS and a simple protein precipitation procedure, was developed and validated. Also, the present method was successfully applied to the determination of BAPTA-AM plasma concentrations for pharmacokinetic studies in rats. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Determination of clavulanic acid in calf plasma by liquid chromatography tandem mass spectrometry

    JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2006
    Tim Reyns
    Abstract A method for the quantification of clavulanic acid in calf plasma using high-performance liquid chromatography combined with electrospray ionization (ESI) mass spectrometry, operating in the negative ionization mode (LC-MS/MS), is presented. Sample preparation includes a simple and fast deproteinization with acetonitrile and a back-extraction of the acetonitrile with dichloromethane. Chromatography is performed on a reversed-phase PLRP-S polymeric column using 0.05% formic acid in water and acetonitrile. The limit of quantification is 25 ng/ml, which is lower than other published methods using ultraviolet (UV), fluorimetric or mass spectrometric detection. The limit of detection is calculated to be 3.5 ng/ml. The stability of clavulanic acid was demonstrated according to The Guidelines of Bioanalytical Method Validation of The Food and Drug Administration (FDA): freeze and thaw stability, short-term stability, long-term stability, stock solution stability and postpreparative stability. The method is used in a pharmacokinetic and bioequivalence study of amoxycillin/clavulanic acid formulations in calves. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Acrylamide levels in Finnish foodstuffs analysed with liquid chromatography tandem mass spectrometry

    MOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 2 2007
    Susanna Eerola
    Abstract Sample clean-up and HPLC with tandem mass spectrometric detection (LC-MS/MS) was validated for the routine analysis of acrylamide in various foodstuffs. The method used proved to be reliable and the detection limit for routine monitoring was sensitive enough for foods and drinks (38 ,g/kg for foods and 5 ,g/L for drinks). The RSDs for repeatability and day-to-day variation were below 15% in all food matrices. Two hundred and one samples which included more than 30 different types of food and foods manufactured and prepared in various ways were analysed. The main types of food analysed were potato and cereal-based foods, processed foods (pizza, minced beef meat, meat balls, chicken nuggets, potato-ham casserole and fried bacon) and coffee. Acrylamide was detected at levels, ranging from nondetectable to 1480 ,g/kg level in solid food, with crisp bread exhibiting the highest levels. In drinks, the highest value (29 ,g/L) was found in regular coffee drinks. [source]

    Simultaneous detection of five different 2-hydroxyethyl-DNA adducts formed by ethylene oxide exposure, using a high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry assay

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2008
    Elaine M. Tompkins
    A method has been developed for the simultaneous detection and quantitation of five different 2-hydroxyethyl-DNA (HE-DNA) adducts that could be formed as a result of exposure to ethylene oxide (EO). In addition to the major N7-HE-guanine (N7-HEG) adducts this assay can also measure the less prevalent but potentially more biologically significant N1-HE-2,-deoxyadenosine (N1-HEdA), O6 -HE-2,-deoxyguanosine (O6 -HEdG), N6 -HE-2,-deoxyadenosine (N6 -HEdA) and N3-HE-2,-deoxyuridine adducts (N3-HEdU). The method involves the isolation of HE adducts from the unmodified nucleosides by either neutral thermal hydrolysis or enzymatic digestion, followed by high-performance liquid chromatographic (HPLC) purification, before detection and quantification by liquid chromatography tandem mass spectrometry (LC/MS/MS) using selective reaction monitoring (SRM). The limits of detection were in the range 0.5,25,fmol for each individual adduct, making this one of the most sensitive assays available for the detection of N7-HEG. To illustrate the possible applications of the assay, it has been employed in the measurement of endogenous/background and EO-induced HE adducts in a variety of DNA samples. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    A sodium dodecyl sulfate,polyacrylamide gel electrophoresis,liquid chromatography tandem mass spectrometry analysis of bovine cartilage tissue response to mechanical compression injury and the inflammatory cytokines tumor necrosis factor , and interleukin-1,

    ARTHRITIS & RHEUMATISM, Issue 2 2008
    Anna L. Stevens
    Objective To compare the response of chondrocytes and cartilage matrix to injurious mechanical compression and treatment with interleukin-1, (IL-1,) and tumor necrosis factor , (TNF,), by characterizing proteins lost to the medium from cartilage explant culture. Methods Cartilage explants from young bovine stifle joints were treated with 10 ng/ml of IL-1, or 100 ng/ml of TNF, or were subjected to uniaxial, radially-unconfined injurious compression (50% strain; 100%/second strain rate) and were then cultured for 5 days. Pooled media were subjected to gel-based separation (sodium dodecyl sulfate,polyacrylamide gel electrophoresis) and analysis by liquid chromatography tandem mass spectrometry, and the data were analyzed by Spectrum Mill proteomics software, focusing on protein identification, expression levels, and matrix protein proteolysis. Results More than 250 proteins were detected, including extracellular matrix (ECM) structural proteins, pericellular matrix proteins important in cell,cell interactions, and novel cartilage proteins CD109, platelet-derived growth factor receptor,like, angiopoietin-like 7, and adipocyte enhancer binding protein 1. IL-1, and TNF, caused increased release of chitinase 3,like protein 1 (CHI3L1), CHI3L2, complement factor B, matrix metalloproteinase 3, ECM-1, haptoglobin, serum amyloid A3, and clusterin. Injurious compression caused the release of intracellular proteins, including Grp58, Grp78, ,4-actinin, pyruvate kinase, and vimentin. Injurious compression also caused increased release and evidence of proteolysis of type VI collagen subunits, cartilage oligomeric matrix protein, and fibronectin. Conclusion Overload compression injury caused a loss of cartilage integrity, including matrix damage and cell membrane disruption, which likely occurred through strain-induced mechanical disruption of cells and matrix. IL-1, and TNF, caused the release of proteins associated with an innate immune and stress response by the chondrocytes, which may play a role in host defense against pathogens or may protect cells against stress-induced damage. [source]

    Liquid chromatography tandem mass spectrometry method for determination of bisoprolol in human plasma using d5-bisoprolol as the internal standard

    BIOMEDICAL CHROMATOGRAPHY, Issue 6 2010
    Gang-yi Liu
    Abstract A simple, reliable and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) protocol was developed and validated for quantification of bisoprolol in human plasma. The sample was pretreated with a simple procedure of protein precipitation and an isotope-labeled d5-bisoprolol was used as internal standard. The chromatographic separation was performed on a Capcell Pak C18 MG III column (100,mm × 2.0,mm, 5,µm). The protonated ion of the analyte was detected in positive ionization by multiple reaction monitoring mode. The mass transition pairs of m/z 326.3 , 116.3 and m/z 331.3 , 121.3 were used to detect bisoprolol and the internal standard, respectively. Linearity, accuracy, precision, recovery, matrix effect, dilution test and stability were evaluated during method validation over the range of 0.5,100,ng/mL. The validated method was successfully applied to analyze human plasma samples in a bisoprolol bioavailability study. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Solid-phase extraction and analysis of paroxetine in human plasma by ultra performance liquid chromatography,electrospray ionization mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 2 2010
    Mitesh Bhatt
    Abstract A rapid, sensitive and rugged solid-phase extraction ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for determination of paroxetine in human plasma. The procedure for sample preparation includes simple SPE extraction procedure coupled with Hypersil Gold C18 column (100 mm , 2.1 mm, i.d., 1.9 ,m) with isocratic elution at a flow-rate of 0.350 mL/min and fluoxetine was used as the internal standard. The analysis was performed on a triple-quadrupole tandem mass spectrometer by multiple reactions monitoring mode via electrospray ionization. Using 500 ,L plasma, the methods were validated over the concentration range 0.050,16.710 ng/mL for paroxetine, with a lower limit of quantification of 0.050 ng/mL. The intra- and inter-day precision and accuracy of the quality control samples were within 10.0%. The recovery was 69.2 and 74.4% for paroxetine and fluoxetine respectively. Total run time was only 1.9 min. The method was highly reproducible and gave peaks with excellent chromatography properties. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Determination of quinapril and quinaprilat in human plasma by ultraperformance liquid chromatography,electrospray ionization mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 5 2009
    Bhavesh Dasandi
    Abstract A novel, specific and sensitive ultraperformance liquid chromatography tandem mass spectrometry (UPLC,MS/MS) method was developed for the simultaneous determination of quinapril and its active metabolite quinaprilat in human plasma. The method involves a simple, one-step extraction procedure coupled with an Acquity UPLCÔ BEH C18 column (100 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow-rate of 0.2 mL/min and lisinopril as the internal standard. Detection was performed on a triple-quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionization. Using 250 µL plasma, the methods were validated over the concentration range 5.010,500.374 ng/mL for quinapril and 10.012,1000 ng/mL for quinaprilat, with a lower limit of quantification of 5.010 ng/mL for quinapril and 10.012 ng/mL for quinaprilat. The intra- and inter-day precision and accuracy were within 10.0%. The recovery was 85.8, 62.6 and 61.3% for quinapril, quinaprilat and lisinopril, respectively. Total run time was 3.0 min only. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Analysis of urinary aromatic acids by liquid chromatography tandem mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 12 2008
    Brian Crow
    Abstract The separation and detection of 11 urinary aromatic acids was developed using HPLC-MS/MS. The method features a simple sample preparation involving a single-step dilution with internal standard and a rapid 8 min chromatographic separation. The accuracy was evaluated by the recovery of known spikes between 87 and 110%. Inter- and intra-assay precision (CV) was below 11% in all cases and the analytes were observed to be stable for up to 8 weeks when stored at ,20°C. The method was validated based upon linearity, accuracy, precision and stability and was used to establish reference intervals for children and adults. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Stable isotope dilution analysis of N-acetylaspartic acid in urine by liquid chromatography electrospray ionization tandem mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 9 2007
    Osama Y. Al-Dirbashi
    Abstract N -acetylaspartic acid (NAA) is a specific urinary marker for Canavan disease, an autosomal recessive leukodystrophy. We developed a ,dilute and shoot' stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method for determination of NAA in urine. Deuterated internal standard d3 -NAA was added to untreated urine and the mixture was injected into the LC-MS/MS system operated in the negative ion mode. Chromatography was carried out on a C8 minibore column using 50% acetonitrile solution containing 0.05% formic acid at a flow rate of 0.25 mL/min. The retention time was 1.6 min and the turnaround time was 2.2 min. NAA and d3 -NAA were analyzed in multiple reaction monitoring mode. Calibrators and quality control samples were prepared in pooled control urine. The assay was linear up to 2000 µmol/L with limit of quantification at 1 µmol/L (S/N = 12). Interassay and intraassay coefficients of variation were less than 7% and recovery at three different concentrations was 98.9,102.5%. The LC-MS/MS method for NAA as described involves no extraction and no derivatization, showed no interference and gave excellent recovery with low variability and short analytical time. The method was successfully applied for the retrospective analysis of urine from 21 Canavan disease cases. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Fetal alcohol syndrome (FAS) in C57BL/6 mice detected through proteomics screening of the amniotic fluid,

    BIRTH DEFECTS RESEARCH, Issue 4 2008
    Susmita Datta
    Abstract BACKGROUND: Fetal Alcohol Syndrome (FAS), a severe consequence of the Fetal Alcohol Spectrum Disorders, is associated with craniofacial defects, mental retardation, and stunted growth. Previous studies in C57BL/6J and C57BL/6N mice provide evidence that alcohol-induced pathogenesis follows early changes in gene expression within specific molecular pathways in the embryonic headfold. Whereas the former (B6J) pregnancies carry a high-risk for dysmorphogenesis following maternal exposure to 2.9 g/kg alcohol (two injections spaced 4.0 h apart on gestation day 8), the latter (B6N) pregnancies carry a low-risk for malformations. The present study used this murine model to screen amniotic fluid for biomarkers that could potentially discriminate between FAS-positive and FAS-negative pregnancies. METHODS: B6J and B6N litters were treated with alcohol (exposed) or saline (control) on day 8 of gestation. Amniotic fluid aspirated on day 17 (n = 6 replicate litters per group) was subjected to trypsin digestion for analysis by matrix-assisted laser desorption,time of flight mass spectrometry with the aid of denoising algorithms, statistical testing, and classification methods. RESULTS: We identified several peaks in the proteomics screen that were reduced consistently and specifically in exposed B6J litters. Preliminary characterization by liquid chromatography tandem mass spectrometry and multidimensional protein identification mapped the reduced peaks to alpha fetoprotein (AFP). The predictive strength of AFP deficiency as a biomarker for FAS-positive litters was confirmed by area under the receiver operating characteristic curve. CONCLUSIONS: These findings in genetically susceptible mice support clinical observations in maternal serum that implicate a decrease in AFP levels following prenatal alcohol damage. Birth Defects Research (Part A), 2008. © 2008 Wiley-Liss, Inc. [source]

    An endogenous regulator of inflammation, resolvin E1, modulates osteoclast differentiation and bone resorption

    BRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2008
    B S Herrera
    Background and purpose: The inflammation-resolving lipid mediator resolvin E1 (RvE1) effectively stops inflammation-induced bone loss in vivo in experimental periodontitis. It was of interest to determine whether RvE1 has direct actions on osteoclast (OC) development and bone resorption. Experimental approach: Primary OC cultures derived from mouse bone marrow were treated with RvE1 and analysed for OC differentiation, cell survival and bone substrate resorption. Receptor binding was measured using radiolabelled RvE1. Nuclear factor (NF)-,B activation and Akt phosphorylation were determined with western blotting. Lipid mediator production was assessed with liquid chromatography tandem mass spectrometry. Key results: OC growth and resorption pit formation were markedly decreased in the presence of RvE1. OC differentiation was inhibited by RvE1 as demonstrated by decreased number of multinuclear OC, a delay in the time course of OC development and attenuation of receptor activator of NF-,B ligand-induced nuclear translocation of the p50 subunit of NF-,B. OC survival and apoptosis were not altered by RvE1. Messenger RNA for both receptors of RvE1, ChemR23 and BLT1 is expressed in OC cultures. Leukotriene B4 (LTB4) competed with [3H]RvE1 binding on OC cell membrane preparations, and the LTB4 antagonist U75302 prevented RvE1 inhibition of OC growth, indicating that BLT1 mediates RvE1 actions on OC. Primary OC synthesized the RvE1 precursor 18R -hydroxy-eicosapentaenoic acid and LTB4. Co-incubation of OC with peripheral blood neutrophils resulted in transcellular RvE1 biosynthesis. Conclusions and implications: These results indicate that RvE1 inhibits OC growth and bone resorption by interfering with OC differentiation. The bone-sparing actions of RvE1 are in addition to inflammation resolution, a direct action in bone remodelling. British Journal of Pharmacology (2008) 155, 1214,1223; doi:10.1038/bjp.2008.367; published online 22 September 2008 [source]

    Differentiation of configurations of the phenylbutenoid dimer derivatives from Zingiber cassumunar by tandem mass spectrometry

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2009
    Juanjuan Chen
    High-performance liquid chromatography/electrospray tandem mass spectrometry was developed to distinguish isomers and compounds of similar structures with different configurations in the rhizomes of Z. cassumunar. Energy-resolved breakdown curves were utilized to differentiate four compounds. Compounds 2 (3R,4S) and 4 (3R,4R) were a pair of stereoisomers which could be distinguished easily by breakdown curves. The breakdown curve of compound 1 was identical to that of compound 2, which suggested that the configuration of compound 1 was (3R,4S) or (3S,4R). The breakdown curve of compound 3 was completely different from those of compounds 1, 2 and 4, and it might be that the configuration of the double bond of compound 3 was different from the other three compounds. Hence, the described method using breakdown curves has great potential in the distinguishing of isomers and compounds of similar structure with different configurations. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Determination of iodoacetic acid using liquid chromatography/electrospray tandem mass spectrometry

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2008
    Benjamin P.-Y.
    A rapid analytical method based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) using electrospray ionization in negative ion detection mode was developed for the analysis of underivatized iodoacetic acid in water. The method was applied to model reaction mixtures in the study of the formation of iodoacetic acid after chlorinated tap water was boiled in the presence of potassium iodide or iodized table salt. Samples can be directly analyzed by the LC/MS/MS system without extraction or chemical derivatization. Limit of detection was determined to be 0.3,µg/L (or 0.3,ng/mL) and limit of quantitation was about 1,µg/L (1,ng/mL). Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Lipidomic analysis of twenty-seven prostanoids and isoprostanes by liquid chromatography/electrospray tandem mass spectrometry

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2006
    Mojgan Masoodi
    Prostanoids are potent mediators of many physiological and pathophysiological processes. Of the many analytical methodologies used for their qualitative and quantitative analysis, electrospray tandem mass spectrometry coupled to liquid chromatography (LC/ESI-MS/MS) offers a rapid, sensitive and versatile system applicable to lipidomic analyses. We have developed an LC/ESI-MS/MS assay for twenty-seven mediators including prostaglandins, prostacyclines, thromboxanes, dihydroprostaglandins and isoprostanes. The assay was liner over the concentration range 1,100 pg/µL. The limits of detection and quantitation were 0.5,50 and 2,100 pg, respectively, whilst recoveries were from 83,116% depending on the metabolite. The assay can be applied to the profiling of prostanoids produced by a variety of biological fluids and extracts including brain, liver, plasma and urine, thus facilitating our understanding of the role of these lipid mediators in health and disease, as well as assisting in drug development. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Determination of levetiracetam in human plasma by liquid chromatography/electrospray tandem mass spectrometry and its application to bioequivalence studies

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2006
    Deepak S. Jain
    The first liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of levetiracetam, an antiepileptic drug, in human plasma is described. The plasma filtrate obtained after solid-phase extraction (SPE), using a polymer-based, hydrophilic-lipophilic balanced (HLB) cartridge, was submitted directly to a short column LC/MS/MS assay. There was no significant matrix effect on the analysis. For validation of the method, the recovery of the free analytes was compared to that from an optimized extraction method, and the analyte stability was examined under conditions mimicking sample storage, handling, and analytical procedures. The extraction procedure yielded extremely clean extracts with a recovery of 79.95% and 89.02% for levetiracetam and the internal standard (IS), respectively. The intra-assay and inter-assay precision for the samples at the lower limit of quantitation (LLOQ) were 6.33 and 6.82%, respectively. The calibration curves were linear for the dynamic range of 0.5 to 50,µg/mL with a correlation coefficient r,,,0.9971. The intra-assay accuracy at LLOQ, LQC, MQC, and HQC levels ranged from 81.60 to 95.40, 93.00 to 103.47, 95.97 to 104.09, and 91.15 to 95.18%, respectively, while the inter-assay accuracy at LLOQ, LQC, MQC and HQC levels varied from 80.20 to 95.40, 88.53 to 107.53, 95.97 to 108.45, and 91.15 to 112.70%, respectively. The method is rugged and fast with a total instrumental run time of 2,min. The method was successfully applied for bioequivalence studies in human subject samples after oral administration of 1000,mg immediate release (IR) formulations. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Simultaneous determination of t,t -muconic, S -phenylmercapturic and S -benzylmercapturic acids in urine by a rapid and sensitive liquid chromatography/electrospray tandem mass spectrometry method

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2004
    Anna Barbieri
    We describe a rapid and sensitive high-performance liquid chromatography/electrospray tandem mass spectrometry (HPLC/ESI-MS/MS) method for simultaneous determination of the most relevant metabolites of benzene and toluene, t,t- muconic acid (t,t -MA), S -phenylmercapturic acid (S-PMA), and S -benzylmercapturic acid (S-BMA). Urine samples were purified before analysis by solid-phase microextraction (SPE) on SAX cartridges with 50,mg sorbent mass. The developed method fulfils all the standard requirements of precision and accuracy. Calibration curves were linear within the concentration range of the standards (0,80,,g/Lurine for t,t -MA, and 0,25,,g/Lurine for S-PMA and S-BMA), and had correlation coefficients ,0.997. Limits of detection were 6.0,,g/L for t,t -MA, 0.3,,g/L for S-PMA, and 0.4,,g/L for S-BMA. The method was used to determine t,t -MA, S-PMA and S-BMA levels in urine of 31 gasoline-station workers, with personal monitoring data obtained from radial symmetry passive diffusive samplers. In the context of mean work-shift exposures of 75.9,,g/m3 (range 9.4,220.2) for benzene and 331.9,,g/m3 (78.2,932.1) for toluene, metabolite concentrations in end-of-shift urine samples ranged from 23.5,275.3,,g/gcreatinine for t,t -MA, non-detectable to 0.9,,g/gcreatinine for S-PMA, and 3.8,74.8,,g/gcreatinine for S-BMA. No significant correlation was found between the environmental concentrations and urinary metabolites (p,>,0.05 for all cases); the ratios of benzene metabolites could be influenced by exposure levels and co-exposure to xylenes and toluene. The high throughput of this procedure should facilitate exploration of the metabolic effects of benzene-related co-exposure to toluene and alkylbenzenes in large populations of subjects exposed to gasoline. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Congener-specific analysis of hexabromocyclododecane by high-performance liquid chromatography/electrospray tandem mass spectrometry

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2003
    Wesley Budakowski
    A congener-specific method based on high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ES-MS/MS) in the negative ion mode was developed for the analysis of hexabromocyclododecane (HBCDD). On a C18 analytical column, with a methanol/water mobile phase, the , -isomer was completely resolved from the , - and , -isomers while the , - and , -isomers were sufficiently resolved at half their peak heights. The ES spray voltage strongly influenced the intensity of the ion signal. For MS, a source temperature of 500°C and a collision energy of 50,eV were found to be optimum for the [M,H], to Br, transition. Run-to-run and day-to-day (n,=,3) variability was minimal, with relative standard deviations of 2.6,4.1 and 2.4,4.4%, respectively. The limit of detection was 4,6,pg on-column. When applied to tissue samples from Lake Winnipeg fish both , - and , -isomers of HBCDD were found in low-ng/g (lipid corrected) concentrations. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Rapid method for determination of chlormequat residues in tomato products by ion-exchange liquid chromatography/electrospray tandem mass spectrometry

    RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2002
    M. Careri
    A rapid method has been devised for the direct determination of chlormequat in tomato samples. No clean-up is required, and analysis uses ion-exchange liquid chromatography/tandem mass spectrometry interfaced with electrospray ionization (LC/ESI-MS/MS). A cation-exchange column was used with an aqueous ammonium acetate/acetonitrile mixture as the mobile phase under isocratic conditions. The method was validated in terms of detection limits (LOD), quantitation limits (LOQ), linearity, recovery, precision and accuracy. Good results in the low,µg kg,1 level were obtained for the LOD and LOQ of chlormequat in tomato samples. Comparison of solvent and matrix-matched calibration curves demonstrated the absence of significant matrix effects and the feasibility of using external calibration. Linearity was established over two orders of magnitude by performing homoscedasticity and Mandel fitting statistical tests. The absence of both constant and proportional systematic errors was verified by evaluating the recovery function, demonstrating good method accuracy. Excellent precision in terms of intra-day repeatability was calculated (RSD% <3.4). Extraction recoveries from tomato products were calculated, by using a labelled internal standard (d4 -chlormequat), to be in the 93,±,5,99,±,7% range. The applicability of the method to the determination of chlormequat residues in tomato products was demonstrated. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Determination of faropenem in human plasma and urine by liquid chromatography,tandem mass spectrometry

    BIOMEDICAL CHROMATOGRAPHY, Issue 1 2008
    Shouhong Gao
    Abstract A simple, rapid and sensitive liquid chromatography/electrospray tandem mass spectrometry (LC-MS/MS) quantitative detection method, using cefalexin as internal standard, was developed for the analysis of faropenem in human plasma and urine. After precipitation of the plasma proteins with acetonitrile, the analytes were separated on a C18 reversed-phase column with 0.1% formic acid,methanol (45:55, v/v) and detected by electrospray ionization mass spectrometry in positive multiple reaction monitoring mode. Calibration curves with good linearities (r = 0.9991 for plasma sample and r = 0.9993 for urine sample) were obtained in the range 5,4000 ng/mL for faropenem. The limit of detection was 5 ng/mL. Recoveries were around 90% for the extraction from human plasma, and good precision and accuracy were achieved. This method is feasible for the evaluation of pharmacokinetic profiles of faropenem in humans, and to our knowledge, it is the first time the pharmacokinetic of faropenem has been elucidated in vivo using LC-MS/MS. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Determination of lamivudine/stavudine/efavirenz in human serum using liquid chromatography/electrospray tandem mass spectrometry with ionization polarity switch

    BIOMEDICAL CHROMATOGRAPHY, Issue 6 2002
    Bin Fan
    A high-performance liquid chromatography/tandem mass spectrometry (LC-MS-MS) method with ionization polarity switch was developed and validated in human serum for the determination of a lamivudine (3TC)/stavudine (d4T)/efavirenz combination HIV therapy. Solid phase extraction (SPE) was used to extract these anti-HIV drugs and internal standard aprobarbital. A gradient mobile phase consisting of acetonitrile and 20,mM ammonium acetate buffer with pH adjusted to 4.5 using glacial acetic acid was utilized to separate these drugs on a hexylsilane column (150,×,2.0,mm i.d.). The total run time between injections was 18,min. The precursor and major product ions of these drugs were monitored on a triple quadrupole mass spectrometer in the multiple reactions monitoring (MRM) mode. Ionization polarity was switched in the middle of the LC run allowing these anti-HIV drugs with different physicochemical properties to be detected simultaneously. The effect of ion suppression from human serum was studied and no interference with the analysis was noted. The method was validated over the range of 1.1,540,ng/mL for 3TC, 12.5,6228,ng/mL for d4T and 1.0,519,ng/mL for efavirenz. The method was shown to be accurate, with intra-day and inter-day accuracy less than 14.0% and precise, with intra-day and inter-day precision less than 13.1%. The extraction recoveries of all analytes were higher than 90%. Copyright © 2002 John Wiley & Sons, Ltd. [source]