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Tandem Mass Spectrometric (tandem + mass_spectrometric)
Terms modified by Tandem Mass Spectrometric Selected AbstractsCyanobacterial neurotoxin BMAA in ALS and Alzheimer's diseaseACTA NEUROLOGICA SCANDINAVICA, Issue 4 2009J. Pablo Objective,,, The aim of this study was to screen for and quantify the neurotoxic amino acid ,- N -methylamino- l -alanine (BMAA) in a cohort of autopsy specimens taken from Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and non-neurological controls. BMAA is produced by cyanobacteria found in a variety of freshwater, marine, and terrestrial habitats. The possibility of geographically broad human exposure to BMAA had been suggested by the discovery of BMAA in brain tissues of Chamorro patients with ALS/Parkinsonism dementia complex from Guam and more recently in AD patients from North America. These observations warranted an independent study of possible BMAA exposures outside of the Guam ecosystem. Methods,,, Postmortem brain specimens were taken from neuropathologically confirmed cases of 13 ALS, 12 AD, 8 HD patients, and 12 age-matched non-neurological controls. BMAA was quantified using a validated fluorescent HPLC method previously used to detect BMAA in patients from Guam. Tandem mass spectrometric (MS) analysis was carried out to confirm the identification of BMAA in neurological specimens. Results,,, We detected and quantified BMAA in neuroproteins from postmortem brain tissue of patients from the United States who died with sporadic AD and ALS but not HD. Incidental detections observed in two out of the 24 regions were analyzed from the controls. The concentrations of BMAA were below what had been reported previously in Chamarro ALS/ Parkinsonism dementia complex patients, but demonstrated a twofold range across disease and regional brain area comparisons. The presence of BMAA in these patients was confirmed by triple quadrupole liquid chromatography/mass spectrometry/mass spectrometry. Conclusions,,, The occurrence of BMAA in North American ALS and AD patients suggests the possibility of a gene/environment interaction, with BMAA triggering neurodegeneration in vulnerable individuals. [source] Development and validation of a liquid chromatographic/tandem mass spectrometric assay for the quantitation of nucleoside HIV reverse transcriptase inhibitors in biological matricesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2005Séverine Compain Abstract Besides liquid chromatographic (LC)/UV methods adapted to therapeutic drug monitoring, there is still a need for more powerful techniques that can be used for pharmacological research and clinical purposes. We developed an LC method coupled with tandem mass spectrometry (MS/MS) to separate, detect and quantify with high sensitivity the nucleoside analogues used in multitherapies (zidovudine, stavudine, zalcitabine, didanosine, lamivudine and abacavir) in plasma and in the intracellular medium. We worked on two essential issues: (i) the need to use two ionization modes in order to achieve the best sensitivity, which leads to the optimization of the chromatographic separation of drugs detected in the positive ionization mode and drugs detected in the negative ionization mode, and (ii) the need to optimize the extraction step in order to enhance sample recovery. The peripheral blood mononuclear cells were lysed in Tris buffer,MeOH. A clean-up procedure was performed by solid-phase extraction only for plasma samples. The LC separation was carried out on a Zorbax Stable Bond C18 column followed by MS/MS analysis after electrospray ionization in either the negative or positive mode. The positive ionization mode was applied at the beginning of the run to detect zalcitabine and lamivudine, then the ionization mode was changed to negative for the detection of didanosine, stavudine, internal standard and zidovudine. The calibration range for all the analytes was 0.5,200 ng ml,1. The recoveries were between 64 and 90%, with coefficients of variation (CVs) lower than 15%. The inaccuracy (bias) was ±15% with CVs always lower than 12%. The analytes were stable at room temperature and in the extraction solvent for at least 24 h, after storage at ,80 °C for 3 months, after three freeze,thaw cycles and in the injection solvent after 48 h at 4 °C. Together with the measurement of intracellular triphosphorylated metabolites thanks to the powerful plasma and intracellular assay method for intact drugs, it is possible to describe the behaviour of nucleoside analogues against HIV through plasma pharmacokinetics, cell membrane diffusion including drug transport involvement, and also the intracellular metabolism. Copyright © 2005 John Wiley & Sons, Ltd. [source] Quantitative analysis of the P-glycoprotein inhibitor Elacridar (GF120918) in human and dog plasma using liquid chromatography with tandem mass spectrometric detectionJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2004Ellen Stokvis Abstract A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method for the determination of the P-glycoprotein and breast cancer resistance protein inhibitor Elacridar in human and dog plasma is described. The internal standard was stable isotopically labelled Elacridar. Sample pretreatment involved liquid,liquid extraction with tert -butyl methyl ether. Analysis of Elacridar and internal standard was performed by reversed-phase LC on a basic stable minibore analytical column with an eluent consisting of acetonitrile and aqueous ammonia. An API-2000 triple-quadrupole mass spectrometer with an electrospray ion source was used in the positive-ion multiple reaction monitoring mode. The run time per sample was only 6 min. The method is sensitive and specific, with a dynamic range from 1 to 500 ng ml,1 from 100 µl of human or dog plasma. The accuracy of the method was within 15% bias and the precision was lower than 15% for all tested concentration levels and in both matrices. The method is simple and the liquid,liquid extraction produces clean samples. This method was successfully applied to support the pharmacokinetics of a clinical trial in which orally applied Elacridar was used as a bioavailability enhancer. Copyright © 2004 John Wiley & Sons, Ltd. [source] Systematic investigation of ion suppression and enhancement effects of fourteen stable-isotope-labeled internal standards by their native analogues using atmospheric-pressure chemical ionization and electrospray ionization and the relevance for multi-analyte liquid chromatographic/mass spectrometric proceduresRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2010Daniela Remane In clinical and forensic toxicology, multi-analyte procedures are very useful to quantify drugs and poisons of different classes in one run. For liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multi-analyte procedures, often only a limited number of stable-isotope-labeled internal standards (SIL-ISs) are available. If an SIL-IS is used for quantification of other analytes, it must be excluded that the co-eluting native analyte influences its ionization. Therefore, the effect of ion suppression and enhancement of fourteen SIL-ISs caused by their native analogues has been studied. It could be shown that the native analyte concentration influenced the extent of ion suppression and enhancement effects leading to more suppression with increasing analyte concentration especially when electrospray ionization (ESI) was used. Using atmospheric-pressure chemical ionization (APCI), methanolic solution showed mainly enhancement effects, whereas no ion suppression and enhancement effect, with one exception, occurred when plasma extracts were used under these conditions. Such differences were not observed using ESI. With ESI, eleven SIL-ISs showed relevant suppression effects, but only one analyte showed suppression effects when APCI was used. The presented study showed that ion suppression and enhancement tests using matrix-based samples of different sources are essential for the selection of ISs, particularly if used for several analytes to avoid incorrect quantification. In conclusion, only SIL-ISs should be selected for which no suppression and enhancement effects can be observed. If not enough ISs are free of ionization interferences, a different ionization technique should be considered. Copyright © 2010 John Wiley & Sons, Ltd. [source] Determination of bupivacaine and metabolites in rat urine using capillary electrophoresis with mass spectrometric detectionELECTROPHORESIS, Issue 14 2003Ryan M. Krisko Abstract A method using capillary electrophoresis-mass spectrometry (CE-MS) was developed for the structural elucidation of bupivacaine and metabolites in rat urine. Prior to CE-MS analysis, solid-phase extraction (SPE) was used for sample cleanup and preconcentration purposes. Exact mass and tandem mass spectrometric (MS/MS) experiments were performed to obtain structural information about the unknown metabolites. Two instruments with different mass analyzers were used for mass spectrometric detection. A quadrupole time-of-flight (Q-TOF) and a magnetic sector hybrid instrument were coupled to CE and used for the analysis of urine extracts. Hydroxybupivacaine as well as five other isomerically different metabolites were detected including methoxylated bupivacaine. [source] High-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry for the determination of flocoumafen and brodifacoum in whole bloodJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2007Mi-cong Jin Abstract A high-performance liquid chromatographic,tandem mass spectrometric (HPLC,MS,MS) assay was developed and validated to determine quantitatively flocoumafen and brodifacoum in whole blood using warfarin as an internal standard (IS). Liquid,liquid extraction, using ethyl acetate, was used to isolate flocoumafen, brodifacoum and the IS from the biological matrix. Detection was performed on a mass spectrometer by negative electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The calibration curves were linear (r2 > 0.998) in the concentration range of 0.1,100.0 ng ml,1 with a lower limit of quantification of 0.05 ng ml,1 for flocoumafen, and 0.1 ng ml,1 for brodifacoum in whole blood. Intra-day and inter-day relative standard deviations (RSDs) were less than 8.0% and 10.8%, respectively. Recoveries of flocoumafen and brodifacoum ranged from 78.0% to 83.7%. This assay can be used to determine trace flocoumafen and brodifacoum in whole blood to investigate suspected poisoning of human and animals. Copyright © 2006 John Wiley & Sons, Ltd. [source] Combination of liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry for the detection of 21 anabolic steroid residues in bovine urineJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2005Christof Van Poucke Abstract For the detection of anabolic steroid residues in bovine urine, a highly sensitive liquid chromatographic/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method was developed using both positive and negative ionization. For four compounds the ESI mode was not sensitive enough and gas chromatographic/mass spectrometric GC/MS detection was therefore still necessary as a complementary method. The sample clean-up consisted of solid-phase extraction (SPE) on a C18 column followed by enzymatic hydrolysis and a second solid-phase extraction on a combination of a C18 and a NH2 column. After this last SPE clean-up, the eluate was split into two equal aliquots. One aliquot was further purified and after derivatization used for GC/MS analysis. The other aliquot was analyzed with LC/MS/MS in both ESI+ and ESI, modes. The method was validated according to the European Commission Decision 2002/657/EC. Decision limits (CC,) were between 0.16 and 1 ng ml,1 for the compounds detected with the LC/MS/MS method. The developed method is used in routine analysis in our laboratory. Copyright © 2005 John Wiley & Sons, Ltd. [source] Isomer separation of hyperbranched polyesteramides with gas-phase H/D exchange and a novel MSn approach: DoDIPJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2002Sander Koster Abstract Two approaches are introduced that provide information about the isomeric composition of hyperbranched polyesteramides. The first approach is based on a novel tandem mass spectrometric (MSn) approach that allows the study of different types of isomeric structures by a separation based on their difference in appearance energy. The method is called DoDIP: dissociation of depleted ion populations. A first MS/MS step is used to fragment isomers with relatively low appearance energy. The isomers with higher appearance energy are fragmented in a second MS/MS step of higher energy. The second approach is based on gas-phase H/D exchange experiments that result in a bimodal isotopic distribution for oligomers XnDn+1 of which one distribution corresponds to a type of isomeric structure that exhibits H/D exchange behaviour and the other to an isomeric structure that does not exhibit H/D exchange behaviour. X is a difunctional anhydride of phthalic acid (P), 1,2-cyclohexanedicarboxylic acid (C), succinic acid (S) or glutaric acid (G). D in XnDn+1 is a trifunctional diisopropanolamine and n the degree of polymerization. The type of isomeric structure that does not exhibit H/D exchange behaviour has a non-alternating monomer sequence that contains an amine bond with a relatively high proton affinity. The other isomeric structure that does exhibit H/D exchange behaviour has an alternating monomer sequence containing only amide and ester bonds with relatively low proton affinity. Oligomer structures were confirmed with additional MS2 experiments after H/D exchange. H/D exchange experiments on the fragments obtained after MS2 of the parent ion show that next to previously postulated mechanisms for the cleavage of the ester and amide bond another reaction pathway must be operational. A new mechanism is introduced to explain the H/D exchange behaviour of the fragments that requires a cleavage of the amide bonds only. Two types of fragments are formed by this mechanism. One type is protonated due to the cleavage of the amide bond whereas the other type has an oxazolonium ion structure due to the loss of an additional H2O. Copyright © 2002 John Wiley & Sons, Ltd. [source] Characterization of protostane triterpenoids in Alisma orientalis by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2010Xin Liu A reliable and sensitive ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) method has been optimized and established for analysis of protostane triterpenoids in a commonly used traditional Chinese herbal medicine Alisma orientalis (Sam.) Juzep. The separation of crude extract of A. orientalis was achieved on a Waters ACQUITY HSS T3 column (100,mm,×,2.1,mm, 1.8,µm) eluting with 0.1% (v/v) formic acid/acetonitrile. A total of 20 protostane triterpenoids including 19 known compounds and a new one were well separated within 7,min. The collision-induced dissociation (CID) tandem mass spectrometric (MS/MS) fragmentation patterns of protostane triterpenoids was firstly reported in this study. The hydrogen rearrangement at the C-23-OH leads to dissociation of the bond between C-23 and C-24 in the protostane triterpenoid skeleton during the CID process. This dissociation was the characteristic CID fragmentation pathway of this class of triterpenoids, and was useful for further differentiation of some positional isomers which contain an acetyl unit on the C-23 or C-24 position. The identities of isolated compounds were identified by comparing their retention times and CID fragmentation behaviors with those of reference standards or tentatively assigned by matching the empirical molecular formulae with those reported in the literature. It is concluded that this newly established UPLC/Q-TOF-MS method is a powerful approach for structural elucidation of protostane triterpenoids isolated from A. orientalis. Copyright © 2010 John Wiley & Sons, Ltd. [source] Cysteine-reactive covalent capture tags for enrichment of cysteine-containing peptidesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2009Priscille Giron Considering the tremendous complexity and the wide dynamic range of protein samples from biological origin and their proteolytic peptide mixtures, proteomics largely requires simplification strategies. One common approach to reduce sample complexity is to target a particular amino acid in proteins or peptides, such as cysteine (Cys), with chemical tags in order to reduce the analysis to a subset of the whole proteome. The present work describes the synthesis and the use of two new cysteinyl tags, so-called cysteine-reactive covalent capture tags (C3T), for the isolation of Cys-containing peptides. These bifunctional molecules were specifically designed to react with cysteines through iodoacetyl and acryloyl moieties and permit efficient selection of the tagged peptides. To do so, a thioproline was chosen as the isolating group to form, after a deprotection/activation step, a thiazolidine with an aldehyde resin by the covalent capture (CC) method. The applicability of the enrichment strategy was demonstrated on small synthetic peptides as well as on peptides derived from digested proteins. Mass spectrometric (MS) analysis and tandem mass spectrometric (MS/MS) sequencing confirmed the efficient and straightforward selection of the cysteine-containing peptides. The combination of C3T and CC methods provides an effective alternative to reduce sample complexity and access low abundance proteins. Copyright © 2009 John Wiley & Sons, Ltd. [source] Can density functional theory (DFT) be used as an aid to a deeper understanding of tandem mass spectrometric fragmentation pathways?RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009Alexander Alex Prediction of tandem mass spectrometric (MS/MS) fragmentation for non-peptidic molecules based on structure is of immense interest to the mass spectrometrist. If a reliable approach to MS/MS prediction could be achieved its impact within the pharmaceutical industry could be immense. Many publications have stressed that the fragmentation of a molecular ion or protonated molecule is a complex process that depends on many parameters, making prediction difficult. Commercial prediction software relies on a collection of general heuristic rules of fragmentation, which involve cleaving every bond in the structure to produce a list of ,expected' masses which can be compared with the experimental data. These approaches do not take into account the thermodynamic or molecular orbital effects that impact on the molecule at the point of protonation which could influence the potential sites of bond cleavage based on the structural motif. A series of compounds have been studied by examining the experimentally derived high-resolution MS/MS data and comparing it with the in silico modelling of the neutral and protonated structures. The effect that protonation at specific sites can have on the bond lengths has also been determined. We have calculated the thermodynamically most stable protonated species and have observed how that information can help predict the cleavage site for that ion. The data have shown that this use of in silico techniques could be a possible way to predict MS/MS spectra. Copyright © 2009 John Wiley & Sons, Ltd. [source] On-chip solid-phase extraction pre-concentration/focusing substrates coupled to atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for high sensitivity biomolecule analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2009Arti Navare Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) has proven a convenient and rapid method for ion production in the mass spectrometric (MS) analysis of biomolecules. AP-MALDI and electrospray ionization (ESI) sources are easily interchangeable in most mass spectrometers. However, AP-MALDI suffers from less-than-optimal sensitivity due to ion losses during transport from the atmosphere into the vacuum of the mass spectrometer. Here, we study the signal-to-noise ratio (S/N) gains observed when an on-chip dynamic pre-concentration/focusing approach is coupled to AP-MALDI for the MS analysis of neuropeptides and protein digests. It was found that, in comparison with conventional AP-MALDI targets, focusing targets showed (1) a sensitivity enhancement of approximately two orders of magnitude with S/N gains of 200,900 for hydrophobic substrates, and 150,400 for weak cation-exchange (WCX) substrates; (2) improved detection limits as low as 5,fmol/µL for standard peptides; (3) significantly reduced matrix background; and (4) higher inter-day reproducibility. The improved sensitivity allowed successful tandem mass spectrometric (MS/MS) sequencing of dilute solutions of a derivatized tryptic digest of a protein standard, and enabled the first reported AP-MALDI MS detection of neuropeptides from Aedes aegypti mosquito heads. Copyright © 2009 John Wiley & Sons, Ltd. [source] Glutamine deamidation of a recombinant monoclonal antibodyRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2008Hongcheng Liu Deamidation of glutamine (Gln) proceeds at a much slower rate than deamidation of asparagine (Asn) residues at peptide level. However, deamidation of Gln residues in native proteins may occur faster because of the impact of protein structure and thus plays a significant role in affecting protein stability. Gln deamidation of a recombinant monoclonal IgG1 antibody was investigated in the current study. Deamidation was determined by a molecular weight increase of 1,Da, a retention time shift on reversed-phase chromatography and tandem mass spectrometric (MS/MS) analysis of the peptides. As expected, Gln residues at different locations in the three-dimensional structure had different susceptibilities to deamidation. Gln deamidation was highly pH dependent with the highest level detected in the sample incubated at pH 9, and lowest level at pH 6 in the pH range from 5 to 9. The detection of significant levels of Gln deamidation suggested that it may play an important role in affecting heterogeneity and stability of recombinant monoclonal antibodies. Copyright © 2008 John Wiley & Sons, Ltd. [source] Differentiation of isomeric flavone/isoflavone aglycones by MS2 ion trap mass spectrometry and a double neutral loss of CORAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2003Fabian Kuhn The fragmentation behaviour of seven pairs of isomeric flavone/isoflavone aglycones (solely hydroxylated and/or methoxylated) was studied using ion trap mass spectrometry with atmospheric pressure ionisation (API, both electrospray and APCI) in the positive and negative ion modes. A major difference was found in the neutral loss of 56,u, which was a common feature of all isoflavones in API(+). It was identified as a double loss of CO by accurate mass tandem mass spectrometric (MS/MS) measurements using a hybrid quadrupole time-of-flight (Q-TOF) instrument. Fragmentation of daidzein with 13C-isotope labelling of the carbon C2 showed that this double loss occurred from the central ring of the molecule. A mechanism for this selective fragmentation is given. Further isoflavone-specific fragmentations were used to develop a guideline for the identification of isoflavone structures. A software-based neutral loss scan of 56,u in the API(+)-MS2 mode was applied to extracts of leaves of Lupinusalbus and to soy flour. The structure elucidation guideline allowed identification of hydroxy and/or methoxy isoflavones. Structures could be confirmed for those available as reference compounds. Copyright © 2003 John Wiley & Sons, Ltd. [source] Dodging matrix effects in liquid chromatography tandem mass spectrometric assays,compilation of key learnings and perspectivesBIOMEDICAL CHROMATOGRAPHY, Issue 5 2009Nuggehally R. Srinivas Abstract Triple quad liquid chromatography mass spectrometric assays (LC/MS/MS) have revolutionized the analysis of drug(s)/metabolite(s) with exceptional speed, sensitivity and selectivity features. From inception to date, several new and innovative features have been regularly proposed by researchers to further enhance the value in the applicability of this analytical tool. However, owing to such compressed run times and scanty sample preparation procedures, LC/MS/MS assays that are not fully optimized generally have issues of matrix effects, where ionization potential is either suppressed or enhanced due to the presence of other materials (endogenous/exogenous) in the matrix. By definition, even co-medications, isomeric or isobaric impurities, and drug excipients used in dosing solutions could also potentially contribute to matrix effects. This article captures some of the interesting work carried out by researchers to understand and handle matrix effects. Additionally, it provides perspectives to effectively deal with matrix effects. Copyright © 2008 John Wiley & Sons, Ltd. [source] Identification and quantification of two antihepatotoxic coumarinolignoids cleomiscosin A and cleomiscosin B in the seeds of Cleome viscosa using liquid chromatography,tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 4 2009Sunil K. Chattopadhyay Abstract A sensitive liquid chromatography/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method was developed for the identification and quantification of two antihepatotoxic coumarinolignoids cleomiscosin A and cleomiscosin B in different extracts of the seeds of Cleome viscosa. The separation of cleomiscosin A and cleomiscosin B was achieved on an RP18 column using a solvent system consisting of a mixture of acetonitrile,methanol (1:2, v/v) and acetonitrile,water,formic acid (5:95:0.3, v/v) as a mobile phase in a gradient elution mode. A multiple-reaction monitoring (MRM) method was developed for quantification of cleomiscosin A and cleomiscosin B in the seed extracts of Cleome viscosa. On the basis of signal-to-noise ratio of 3, the limit of detection in MRM mode for cleomiscosin A and cleomiscosin B were 1.0 and 4.0 ng/mL respectively. The method was validated in terms of linearity, accuracy and precision for 6 days. The method developed was found to be useful for identification and quantification of cleomiscosin A and cleomiscosin B in the different extracts of the seeds of Cleome viscosa. Copyright © 2008 John Wiley & Sons, Ltd. [source] Quantitative determination of ,,, -dimethylacrylshikonin (DASK) in rat whole blood by liquid chromatography,tandem mass spectrometry with pre-column derivation and its pharmacokinetic applicationBIOMEDICAL CHROMATOGRAPHY, Issue 4 2009Huifang Tian Abstract A sensitive and selective liquid chromatography,tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of ,,, -dimethylacrylshikonin (DASK) in rat whole blood. DASK was pretreated using pre-column derivatization with 2-mercaptoethanol followed by liquid,liquid extraction with cyclohexane. Detection was performed on Thermo Finnigan TSQ Quantum triple quadrupole mass spectrometer by selected reaction monitoring mode via electrospray ionization source. The linear range for the determination of DASK spiked in rat whole blood (0.25 mL) was 3,3000 ng/mL. The accuracy was within 9%. Intra- and inter-day precisions were no more than 16.1 and 13.3%, respectively. The validated LC-MS/MS method was successfully applied to the preliminary pharmacokinetic study in rats. After DASK administration (60 mg/kg, p.o.) in rats, pharmacokinetic parameters were obtained, where the area under the drug concentration,time curve was 2393.7 ± 224.4 ng h/mL and the elimination half-life was 27.6 ± 5.3 h. Copyright © 2008 John Wiley & Sons, Ltd. [source] Studies on neurosteroids XXIV.BIOMEDICAL CHROMATOGRAPHY, Issue 12 2008-androstane-, -diol, Determination of neuroactive androgens, androsterone, in rat brain, serum using liquid chromatography, tandem mass spectrometry Abstract The development and validation of liquid chromatography,electrospray ionization,tandem mass spectrometric (LC,ESI-MS/MS) methods that enable the quantification of neuroactive androgens, androsterone (5, -androstan-3, -ol-17-one, 3,,5, -A) and 5, -androstane-3,,17, -diol (3,,5, -Adiol), in the rat brain and serum are presented. The androgens were extracted with methanol,acetic acid, purified using solid-phase extraction cartridges, derivatized with an ESI-active reagent, isonicotinoyl azide (INA), and then subjected to LC,ESI-MS/MS. The quantifications were based on selected reaction monitoring mode using the characteristic transitions of the INA derivatives. The methods allowed the reproducible and accurate quantification of the brain and serum neuroactive androgens using a 100 mg or 100 µL sample; the intra- and inter-assay relative standard deviations were below 3.6%, and the percentage accuracy values were 97.1,103.7% for both androgens. The animal study using the methods suggests that most of 3,,5, -Adiol found in the brain is derived from the periphery, while 3,,5, -A is not only transported from the periphery into the brain, but also synthesized in the brain by the oxidation of 3,,5, -Adiol. The androgens in the rats intraperitoneally administered finasteride, a 5, -reductatse inhibitor, were also measured; this treatment significantly reduced the brain 3,,5, -A and 3,,5, -Adiol levels and increased only the brain level of androstenedione, the precursor of 3,,5, -A. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||