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Triple-quadrupole Mass Spectrometer (triple-quadrupole + mass_spectrometer)
Selected AbstractsCollision-induced dissociation studies of protonated ether,(H2O)n (n = 1,3) clustersJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2006Daniel J. Goebbert Abstract We have studied the protonated ether,(H2O)n (n = 1,3) complexes containing tetrahydrofuran, dimethyl, diethyl, dibutyl, and butylmethyl ethers using a flowing afterglow triple-quadrupole mass spectrometer. Collision-induced dissociation, CID, of all clusters with n = 1, 2 shows sequential water loss. The n = 3 cluster of dimethyl ether shows sequential water loss, while all other ether clusters display selective product formation. The CID spectra are interpreted based on known energetics, and theoretical studies of the dimethyl and diethyl ether systems. Copyright © 2006 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] Targeted comparative proteomics by liquid chromatography/matrix-assisted laser desorption/ionization triple-quadrupole mass spectrometry,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2006Jeremy E. Melanson Here we report the first application of a matrix-assisted laser desorption/ionization (MALDI) triple-quadrupole mass spectrometer for targeted proteomics. Employing an amine-specific isotopic labelling approach, the technique was validated using five randomly selected bovine serum albumin peptides differentially labelled at known ratios. An indirect benefit of the isotopic labelling technique is a significant enhancement of the a1 ion in tandem mass (MS/MS) spectra of all peptides studied. Therefore, the a1 ion was selected as the fragment ion for multiple reaction monitoring (MRM) in all cases, eliminating tedious method development and optimization. Accurate quantification was achieved with an average relative standard deviation (RSD) of 5% (n,=,5) and a detection limit of 14,amol. The technique was then applied to validate an important virulence biomarker of the fungal pathogen Candida albicans, which was not accurately quantified using global proteomics experiment employing two-dimensional liquid chromatography/electrospray ionization tandem mass spectrometry (2D-LC/ESI)-MS/MS. Using LC/MALDI-MRM analysis of five tryptic peptides, the protein PHR1 was found to be upregulated in the hyphal (pathogenic) form of C. albicans by a factor of 7.7,±,0.8. Copyright © 2006 John Wiley & Sons, Ltd. [source] Using a triple-quadrupole mass spectrometer in accurate mass mode and an ion correlation program to identify compounds,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2005Andrew H. Grange Atomic masses and isotopic abundances are independent and complementary properties for discriminating among ion compositions. The number of possible ion compositions is greatly reduced by accurately measuring exact masses of monoisotopic ions and the relative isotopic abundances (RIAs) of the ions greater in mass by +1,Da and +2,Da. When both properties are measured, a mass error limit of 6,10,mDa (<,31,ppm at 320,Da) and an RIA error limit of 10% are generally adequate for determining unique ion compositions for precursor and fragment ions produced from small molecules (less than 320,Da in this study). ,Inherent interferences', i.e., mass peaks seen in the product ion mass spectrum of the monoisotopic [M+H]+ ion of an analyte that are ,2, ,1, +1, or +2,Da different in mass from monoisotopic fragment ion masses, distort measured RIAs. This problem is overcome using an ion correlation program to compare the numbers of atoms of each element in a precursor ion to the sum of those in each fragment ion and its corresponding neutral loss. Synergy occurs when accurate measurement of only one pair of +1,Da and +2,Da RIAs for the precursor ion or a fragment ion rejects all but one possible ion composition for that ion, thereby indirectly rejecting all but one fragment ion-neutral loss combination for other exact masses. A triple-quadrupole mass spectrometer with accurate mass capability, using atmospheric pressure chemical ionization (APCI), was used to measure masses and RIAs of precursor and fragment ions. Nine chemicals were investigated as simulated unknowns. Mass accuracy and RIA accuracy were sufficient to determine unique compositions for all precursor ions and all but two of 40 fragment ions, and the two corresponding neutral losses. Interrogation of the chemical literature provided between one and three possible compounds for each of the nine analytes. This approach for identifying compounds compensates for the lack of commercial ESI and APCI mass spectral libraries, which precludes making tentative identifications based on spectral matches. Published in 2005 by John Wiley & Sons, Ltd. [source] Electrospray ionization mass spectrometric characterization and quantitation of xanthine derivatives using isotopically labelled analogues: an application for equine doping control analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2004Mario Thevis Isotope-dilution mass spectrometry has been employed successfully in numerous fields of analytical chemistry enabling the establishment of fast and reliable procedures. In equine sports, xanthine derivatives such as caffeine and theobromine are prohibited, and doping control laboratories analyze horse urine specimens regarding these illicit performance-enhancing drugs. Theobromine has to exceed a threshold level of 2,,g/mL, hence a robust and reliable quantitation is required. Stably deuterated theobromine and caffeine were synthesized by the reaction of xanthine or theobromine with iodomethane-d3 in the presence of N -methyl- N -trimethylsilyltrifluoroacetamide or potassium carbonate in acetonitrile, respectively. Both compounds were characterized by nuclear magnetic resonance spectroscopy and electrospray ionization tandem mass spectrometry, and a robust and fast assay for the qualitative and quantitative analysis of theobromine in equine urine samples was validated. Urine specimens were extracted by means of solid-phase extraction cartridges, and concentrated extracts were analyzed by liquid chromatography interfaced to a triple-quadrupole mass spectrometer. In addition, the dissociation behavior of deuterated analogues to caffeine and theobromine allowed proposals for fragmentation routes of xanthine derivatives after atmospheric pressure ionization and collisionally activated dissociation. Copyright © 2004 John Wiley & Sons, Ltd. [source] Studies on azaspiracid biotoxins.RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2002In this report, the mass spectral analysis of azaspiracid biotoxins is described. Specifically, the collision-induced dissociation (CID) behavior and differences between CID spectra obtained on a triple-quadrupole, a quadrupole time-of-flight, and an ion-trap mass spectrometer are addressed here. The CID spectra obtained on the triple-quadrupole mass spectrometer allowed the classification of the major product ions of the five investigated compounds (AZA 1,5) into five distinct fragment ion groups, according to the backbone cleavage positions. Although the identification of unknown azaspiracids was difficult based on CID alone, the spectra provided sufficient structural information to allow confirmation of known azaspiracids in marine samples. Furthermore, we were able to detect two new azaspiracid analogs (AZA 1b and 6) in our samples and provide a preliminary structural analysis. The proposed dissociation pathways under tandem mass spectrometry (MS/MS) conditions were confirmed by a comparison with accurate mass data from electrospray quadrupole time-of-flight MS/MS experiments. Regular sequential MSn analysis on an ion-trap mass spectrometer was more restricted in comparison to the triple-quadrupole mass spectrometer, because the azaspiracids underwent multiple [M,+,H,,,nH2O]+ (n,=,1,6) losses from the precursor ion under CID. Thus, the structural information obtained from MSn experiments was somewhat limited. To overcome this limitation, we developed a wide-range excitation technique using a 180-u window that provided results comparable to the triple-quadrupole instrument. To demonstrate the potential of the method, we applied it to the analysis of degraded azaspiracids from mussel tissue extracts. Copyright © 2002 John Wiley & Sons, Ltd. [source] Rapid quantification of lisinopril in human plasma by liquid chromatography/tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 4 2007Weiwei Qin Abstract An assay based on protein precipitation and liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed and validated for the quantitative analysis of lisinopril in human plasma. After the addition of enalaprilat as internal standard (IS), plasma samples were prepared by one-step protein precipitation using perchloric acid followed by an isocratic elution with 10 mm ammonium acetate buffer (pH adjusted to 5.0 with acetic acid),methanol (70:30, v/v) on a Phenomenex Luna 5µC18 (2) column. Detection was performed on a triple-quadrupole mass spectrometer utilizing an electrospray ionization (ESI) interface operating in positive ion and selected reaction monitoring (SRM) mode with the precursor to product ion transitions m/z 406,246 for lisinopril and m/z 349,206 for enalaprilat. Calibration curves of lisinopril in human plasma were linear (r = 0.9973,0.9998) over the concentration range 2,200 ng/mL with acceptable accuracy and precision. The limit of detection and lower limit of quantification in human plasma were 1 and 2 ng/mL, respectively. The validated LC-MS/MS method has been successfully applied to a preliminary pharmacokinetic study of lisinopril in Chinese healthy male volunteers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Rearrangement process occurring in the fragmentation of adefovir derivativesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2004Xiaoyan Chen Abstract The fragmentation of the antiviral drug adefovir dipivoxil and its two active metabolites, adefovir and monopivoxil adefovir, was investigated using both ion trap and triple-quadrupole mass spectrometers. Fragment ions due to loss of 30 Da were observed and attributed to an unanticipated rearrangement process by loss of formaldehyde. The proposed mechanism is supported with the aid of three newly synthesized adefovir derivatives and with accurate mass measurement. Other fragmentations by loss of a pivaloyl group, loss of water, C,P bond cleavage and C,O bond cleavage were also observed for adefovir derivatives. It was concluded that the compounds containing a >POO,CHR,OCO, group generally displayed a rearrangement reaction by loss of RCHO in collision-induced dissociation, and the process generally required an activation energy lower than for a direct bond cleavage. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||