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Liquid Chromatography/quadrupole Time-of-flight Mass Spectrometry (liquid + chromatography_time-of-flight_mass_spectrometry)
Selected AbstractsSuccinimide formation at Asn 55 in the complementarity determining region of a recombinant monoclonal antibody IgG1 heavy chainJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2009Boxu Yan Abstract We investigated the formation and stability of succinimide, an intermediate of deamidation events, in recombinant monoclonal antibodies (mAbs). During the course of an analytical development study of an IgG1 mAbs, we observed that a specific antibody population could be separated from the main product by cation-exchange (CEX) chromatography. The cell-based bioassay measured a ,70% drop in potency for this fraction. Liquid chromatography time-of-flight mass spectrometry (LC,TOF/MS) and tandem mass spectrometry (LC,MS/MS) analyses showed that the modified CEX fraction resulted from the formation of a succinimide intermediate at Asn 55 in the complementarity determining region (CDR) of the heavy chain. Biacore assay revealed a ,50% decrease in ligand binding activity for the succinimide-containing Fab with respect to the native Fab. It was found that the succinimide form existed as a stable intermediate with a half-life of ,3 h at 37°C and pH 7.6. Stress studies indicated that mildly acidic pH conditions (pH 5) favored succinimide accumulation, causing a gradual loss in potency. Hydrolysis of the succinimide resulted in a further drop in potency. The implications of the succinimide formation at Asn 55, a highly conserved residue among IgG1 (mAbs), are discussed. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3509,3521, 2009 [source] Time of flight mass spectrometry applied to the liquid chromatographic analysis of pesticides in water and foodMASS SPECTROMETRY REVIEWS, Issue 6 2006Sķlvia Lacorte Abstract Liquid chromatography coupled to mass spectrometry (LC-MS) is an excellent technique to determine trace levels of polar and thermolabile pesticides and their degradation products in complex matrices. LC-MS can be equipped with several mass analyzers, each of which provides unique features capable to identify, quantify, and resolve ambiguities by selecting appropriate ionization and acquisition parameters. We discuss in this review the use of LC coupled to (quadrupole) time-of-flight mass spectrometry (LC-(Q)ToF-MS) to determine the presence of target and non-target pesticides in water and food. This technique is characterized by operating at a resolving power of 10,000 or more. Therefore, it gives accurate masses for both parent and fragment ions and enables the measurement of the elemental formula of a compound achieving compound identification. In addition, the combination of quadrupole-ToF permits tandem mass spectrometry, provides more structural information, and enhances selectivity. The purpose of this article is to provide an overview on the state of art and applicability of liquid chromatography time-of-flight mass spectrometry (LC-ToF-MS), and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) for the analysis of pesticides in environmental matrices and food. The performance of such techniques is depicted in terms of accurate mass measurement, fragmentation, and selectivity. The final section is devoted to describing the applicability of LC-(Q)ToF-MS to routine analysis of pesticides in food matrices, indicating those operational conditions and criteria used to screen, quantify, and identify target and "suspected" pesticides and their degradation products in water, fruits, and vegetables. The potential and future trends as well as limitations of LC-(Q)ToF-MS for pesticide monitoring are highlighted. © 2006 Wiley Periodicals, Inc. [source] Differentiation of structural isomers in a target drug database by LC/Q-TOFMS using fragmentation predictionDRUG TESTING AND ANALYSIS, Issue 6 2010Elli Tyrkkö Abstract Isomers cannot be differentiated from each other solely based on accurate mass measurement of the compound. A liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOFMS) method was used to systematically fragment a large group of different isomers. Two software programs were used to characterize in silico mass fragmentation of compounds in order to identify characteristic fragments. The software programs employed were ACD/MS Fragmenter (ACD Labs Toronto, Canada), which uses general fragmentation rules to generate fragments based on the structure of a compound, and SmartFormula3D (Bruker Daltonics), which assigns fragments from a mass spectra and calculates the molecular formulae for the ions using accurate mass data. From an in-house toxicology database of 874 drug substances, 48 isomer groups comprising 111 compounds, for which a reference standard was available, were found. The product ion spectra were processed with the two software programs and 1,3 fragments were identified for each compound. In 82% of the cases, the fragment could be identified with both software programs. Only 10 isomer pairs could not be differentiated from each other based on their fragments. These compounds were either diastereomers or position isomers undergoing identical fragmentation. Accurate mass data could be utilized with both software programs for structural elucidation of the fragments. Mean mass accuracy and isotopic pattern match values (SigmaFit; Bruker Daltonics Bremen, Germany) were 0.9 mDa and 24.6 mSigma, respectively. The study introduces a practical approach for preliminary compound identification in a large target database by LC/Q-TOFMS without necessarily possessing reference standards. Copyright © 2010 John Wiley & Sons, Ltd. [source] Toxicological determination and in vitro metabolism of the designer drug methylenedioxypyrovalerone (MPDV) by gas chromatography/mass spectrometry and liquid chromatography/quadrupole time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2010Sabina Strano-Rossi A method for the toxicological screening of the new designer drug methylenedioxypyrovalerone (MDPV) is described; with an emphasis on its application for anti-doping analysis. The metabolism of MDPV was evaluated in vitro using human liver microsomes and S9 cellular fractions for CYP450 phase I and uridine 5,-diphosphoglucuronosyltransferase (UGT) and sulfotransferase (SULT) phase II metabolism studies. The resulting metabolites were subsequently liquid/liquid extracted and analyzed using gas chromatography/mass spectrometry (GC/MS) as trimethylsilyl (TMS) derivatives. The structures of the metabolites were further confirmed by accurate mass measurement using a liquid chromatography/quadrupole time-of-flight (LC/QTOF) mass spectrometer. The studies demonstrated that the main metabolites of MDPV are catechol and methyl catechol pyrovalerone, which are in turn sulfated and glucuronated. The method for the determination of MDPV in urine has been fully validated by assessing the limits of detection and quantification, linearity, repeatability, and accuracy. This validation demonstrates the suitability for screening of this stimulant substance for anti-doping and forensic toxicology purposes. Copyright © 2010 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] | ||||||||||