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Ion Electrospray Ionization (ion + electrospray_ionization)
Kinds of Ion Electrospray Ionization Selected AbstractsA validated liquid chromatographic/tandem mass spectrometric method for the determination of phencyclidine in microliter samples of rat serumJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2005Howard P. Hendrickson Abstract A liquid chromatographic/tandem mass spectrometric method is described for the determination of phencyclidine (PCP) in small volumes of rat serum (e.g. 50 µl). Samples were extracted using a mixed-mode strong cation-exchange column and then separated isocratically using a narrow-bore (2.1 mm i.d.) 3 µm Hypersil phenyl column and a mobile phase consisting of an ammonium formate buffer (pH 2.7) with 60% (v/v) methanol. Detection was accomplished using positive ion electrospray ionization in the multiple reaction monitoring mode. Mass spectra were obtained and peaks were observed at an m/z (% abundance) of 244 (100), 159 (25), and 86 (89). Tandem mass spectra were also obtained from the m/z 244 precursor ion with peaks observed at m/z 159 (100), 86 (96), and 91 (11). Optimum serum PCP sensitivity and precision were obtained at a transition of m/z 244 , 159. Matrix-associated ion suppression did not significantly affect the accuracy (100,112%) or precision (CV ,8%) of the assay. The lower limit of quantitation was 1 ng ml,1 in 50 µl of serum. The method was used to study the serum pharmacokinetics of PCP in rats after an intravenous bolus dose of PCP. Copyright © 2004 John Wiley & Sons, Ltd. [source] Capillary high performance liquid chromatography coupled with electrospray ionization mass spectrometry for rapid analysis of pinane monoterpene glycosides in Cortex MoutanJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2008Yue Song Abstract In this study, a rapid and reliable assay has been developed for quantification of pinane monoterpene glycosides in Cortex Moutan; it is based on capillary high performance liquid chromatography coupled with electrospray ionization mass spectrometry (capillary HPLC,ESI MS). This method utilizes capillary HPLC for the separation of seven pinane monoterpene glycosides in a methanol extract of the botanical sample followed by negative ion electrospray ionization and single ion monitoring (SIM). The compounds of interest in the sample were unambiguously identified on the basis of information about retention time and quasi-molecular ions ([M,H],) or adduct ions ([M+HCOO],). Validation parameters of the method were established. The linearity range was 1.01,105.5 ,g/mL with the square of correlation coefficients lying in the range of 0.9965,0.9997, limits of detection were on the fmol level, the average recoveries varied between 91.8 and 101.0%, and good precision values (RSD, 1.2,4.91%) for peak area were obtained. After validation, the applicability of the method for determination of these pinane monoterpene glycosides in Cortex Moutan has been demonstrated. [source] Quantitative analysis of amyloid , peptides in cerebrospinal fluid of Alzheimer's disease patients by immunoaffinity purification and stable isotope dilution liquid chromatography/negative electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006Tomoyuki Oe The 40 and 42 amino-acid residue forms of amyloid beta (A,1,40 and A,1,42) in cerebrospinal fluid (CSF) have been proposed as potential biomarkers of Alzheimer's disease (AD). Quantitative analyses of A, peptides in CSF have relied almost exclusively on the use of immunoassay-based assays such as the enzyme-linked immunosorbent assay (ELISA) procedure. However, due to the ability of the A, peptides to readily self-aggregate or bind to other proteins and glassware, such analyses are extremely challenging. Analyses are further complicated by the potential of the peptides to undergo post-translational modifications and the possibilities for cross-reaction in the ELISA assays with endogenous components of the CSF. An approach based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) has now been developed which overcomes these methodological issues. The key steps in implementing this new approach involved immunoaffinity purification coupled with the use of [15N]-labeled A, peptides as internal standards, a basic LC mobile phase, negative ion electrospray ionization, and a basic solvent for dissolving the peptides and washing the injection needle to prevent carryover of analytes during multiple injections on the LC/MS system. The validated method had limits of quantitation of 44,fmol/mL (200,pg/mL) for A,1,42 and 92,fmol/mL (400,pg/mL) for A,1,40. An excellent correlation was found between the LC/MS/MS assay and an ELISA assay for A,1,42 in human CSF (r2,=,0.915), although less correlation was observed for A,1,40 (r2,=,0.644). Mean CSF A,1,42 concentrations for samples collected 2 weeks apart from a limited number of AD patients provided additional confidence in the reproducibility of the LC/MS/MS assay. Concentrations for duplicate samples from AD patients were slightly higher than most previously reported values (mean 1.06,±,0.25,ng/mL; n,=,7). A,1,40 concentrations in duplicate samples obtained from AD patients were also reproducible but were found to be slightly lower than most previously reported values (mean 6.36,±,3.07,ng/mL; n,=,7). Consistent with literature reports, mean A,1,42 concentrations were found to be lower in AD patients compared with the normal subjects (mean 1.49,±,0.59,ng/mL; n,=,7), whereas there was no difference in A,1,40 concentrations between AD patients and normal subjects (mean 5.88,±,3.03,ng/mL; n,=,7). The accuracy and precision of the LC/MS assay mean that it will be a useful complement to existing ELISA assays for monitoring therapeutic interventions designed to modulate CSF A,1,42 concentrations in individual AD patients. Moreover, the introduction of stable isotope labeled internal standards offers the potential to achieve a more rigorous account of the influence of methodological effects related to sample collection and processing. Copyright © 2006 John Wiley & Sons, Ltd. [source] Comparison of negative and positive ion electrospray ionization mass spectra of calmodulin and its complex with trifluoperazineRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2005Stephen J. Watt The protein calmodulin (apoCaM) undergoes a conformational change when it binds calcium. This structure of the protein (Ca4CaM) is a dumbbell-shaped molecule that undergoes a further profound conformational change on binding of the antipsychotic drug trifluoperazine (TFP). Experimental conditions were developed to prepare samples of apoCaM, Ca4CaM and Ca4CaM/TFP that were substantially free of sodium. The effects of the conformational changes of calmodulin on the charge-state distributions observed in positive ion and negative ion electrospray ionization (ESI) mass spectra were examined. Conversion of apoCaM into Ca4CaM was concomitant with a change in the negative ion ESI mass spectrum whereby the 16, ion was the most abundant ion observed for the apo form and the 8, ion was the most abundant for the complex. In contrast, in the positive ion ESI mass spectra of apoCaM and Ca4CaM, the most abundant species in each case was the 8+ ion. When a complex of Ca4CaM with TFP was prepared, the most abundant species was the 5+ ion. This is consistent with a conformational change of Ca4CaM that rendered some basic sites inaccessible to ionization in the ESI process. Using the same Ca4CaM/TFP mixture, no complex with TFP was observed in negative ion ESI mass spectra. These observations are discussed in the context of the structural changes that are known to occur in calmodulin, and suggestions are made to explain the apparently conflicting data. The results reported here reflect on the validity of using differences in charge-state distributions observed in ESI mass spectra to assess conformational changes in proteins. Copyright © 2005 John Wiley & Sons, Ltd. [source] Rapid quantification of levosulpiride in human plasma using RP-HPLC-MS/MS for pharmacokinetic and bioequivalence studyBIOMEDICAL CHROMATOGRAPHY, Issue 12 2009Jin-Hee Park Abstract A rapid and validated method for analysis of levosulpiride in human plasma using liquid chromatography coupled to tandem mass spectrometry was developed. Levosulpiride and tiapride (IS, internal standard) were extracted from alkalized plasma samples with ethylacetate and separation by RP-HPLC. Detection was performed by positive ion electrospray ionization in multiple-reaction monitoring mode, monitoring the transitions m/z 342.1 , m/z 112.2 and m/z 329.1 , m/z 213.2, for quantification of levosulpiride and IS, respectively. The standard calibration curves showed good linearity within the range of 2,200 ng/mL (r2 , 0.9990). The lower limit of quantitation was 2 ng/mL. The retention times of levosulpiride (0.63 min) and IS (0.66 min) presented a significant time saving benefit of the proposed method. No significant metabolic compounds were found to interfere with the analysis. This method offered good precision and accuracy and was successfully applied for the pharmacokinetic and bioequivalence study of a 25 mg of levosulpiride tablet in 24 healthy Korean volunteers. Copyright © 2009 John Wiley & Sons, Ltd. [source] Simultaneous determination and pharmacokinetic study of oxymatrine and matrine in beagle dog plasma after oral administration of Kushen formula granule, oxymatrine and matrine by LC-MS/MSBIOMEDICAL CHROMATOGRAPHY, Issue 8 2007Yiqi Wang Abstract A rapid, specific and sensitive LC-MS/MS method was developed for the determination of oxymatrine (OMT) and matrine (MT) in beagle dog plasma. The method was applied to study the pharmacokinetics of OMT and MT after oral administration of OMT, MT and Kushen formula granule (KFG) containing equivalent amounts of OMT and MT in a three-period crossover design. The analysis was carried out on an Acquity UPLCÔ BEH C18 column by linear gradient elution with 0.01% acetic acid,water,methanol as mobile phase. Detection was by positive ion electrospray ionization (ESI) mass spectrometry with multiple-reaction monitoring (MRM). Linear calibration curves were both obtained over the concentration range 15,2000 ng/mL, with a limit of quantification of 15 ng/mL. The matrix effect was minimized. The intra- and inter-day precisions (RSDs) were less than 12.4 and 14.7%, respectively, and the accuracy (RE) was from ,2.1 to 2.7%. The validated method was used to determine the concentration,time profiles of OMT and MT. The results indicated that the absorption of OMT and MT after oral administration of KFG was significantly greater than that after oral administration of pure components. Copyright © 2007 John Wiley & Sons, Ltd. [source] Amlodipine bioequivalence study: quantification by liquid chromatography coupled to tandem mass spectrometryBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 9 2001M. Carvalho Abstract Objective,To assess the bioequivalence of two amlodipine tablet formulations (Amlodipine® 5 mg tablet from Merck S.A. Indústrias Químicas, Brazil as test formulation and Norvasc® 5 mg tablet from Laboratórios Pfizer Ltd., Brazil as reference formulation) in 24 healthy volunteers of both sexes. Methods,The study was conducted using an open, randomized two-period crossover design with a 4-week washout interval. Plasma samples were obtained over a 144 h period. Plasma amlodipine concentrations were analyzed by combined liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) with positive ion electrospray ionization using multiple reaction monitoring (MRM). From the amlodipine plasma concentration vs time curves, the following pharmacokinetic parameters were obtained: AUClast, AUC0,inf and Cmax. The statistical interval proposed was 80,125% according to the US Food and Drug Administration Agency. Results,The limit of quantification was 0.1 ng/ml for plasma amlodipine analysis. The geometric mean and the 90% confidence interval (CI) test/reference ratios were 101.2 (92.9,110.2%) for AUClast, 99.6 (91.5,108.4%) for AUC0,inf and 98.5 (89.0,109.1%) for Cmax. Conclusion,Since the 90% CI for AUClast, AUC0,inf and Cmax ratios were within in the 80,125% interval proposed by the US FDA, it was concluded that Amlodipine® 5 mg tablet (test formulation) was bioequivalent to Norvasc® 5 mg tablet, in terms of both rate and extent of absorption. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||