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Cone Voltage (cone + voltage)
Selected AbstractsInternal energy distribution of peptides in electrospray ionization : ESI and collision-induced dissociation spectra calculationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2008Alireza Pak Abstract The internal energy of ions and the timescale play fundamental roles in mass spectrometry. The main objective of this study is to estimate and compare the internal energy distributions of different ions (different nature, degree of freedom ,DOF' and fragmentations) produced in an electrospray source (ESI) of a triple-quadrupole instrument (Quattro I Micromass). These measurements were performed using both the Survival Yield method (as proposed by De Pauw) and the MassKinetics software (kinetic model introduced by Vékey). The internal energy calibration is the preliminary step for ESI and collision-induced dissociation (CID) spectra calculation. meta -Methyl-benzylpyridinium ion and four protonated peptides (YGGFL, LDIFSDF, LDIFSDFR and RLDIFSDF) were produced using an electrospray source. These ions were used as thermometer probe compounds. Cone voltages (Vc) were linearly correlated with the mean internal energy values ( Optimization of the ESI and APCI experimental variables for the LC/MS determination of s-triazines, methylcarbamates, organophosphorous, benzimidazoles, carboxamide and phenylurea compounds in orange samplesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2007Guilherme M. Titato Abstract In this work, ten selected pesticides of different chemical groups, indicated to orange culture, were extracted and determined by liquid chromatography,mass spectrometry using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) operating in the positive ion detection mode. Applying a variables selection technique verified that cone voltage, source temperature and drying-gas flow-rate are the critical variables when the ESI was used, while cone voltage was found to be the only critical variable for the MS system, operating with the APCI ionization mode. After optimization of the most important parameters through the variables selection technique, the selected ion-recording (SIR) mode, monitoring the [M + H]+ species for all the compounds, was applied for the method validation of the pesticides, in both ionization modes. In orange samples, matrix effects did not interfere with the determination of the pesticides. Pesticides quantification limits ranged from 10 to 50 µg kg,1 for ESI and from 8.2 to 45 µg kg,1 for APCI. Linearity was studied from LOQ upto 200 times LOQ values (r > 0.98). Recoveries obtained were in the range of 70.2,100.5% (RSDs less than 10%). In order to guarantee that the identification and confirmation of the studied pesticides in real samples were unequivocal, characteristic fragment ions of the pesticides were obtained by varying the cone voltage (in-source CID). Copyright © 2007 John Wiley & Sons, Ltd. [source] Structural characterization of hexoses and pentoses using lead cationization.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2002An electrospray ionization, tandem mass spectrometric study Abstract The analytical potential of the complexation of isomeric underivatized hexoses (D -glucose, D -galactose, D -mannose, D -talose, D -fructose), methylglycosides (1- O -methyl-,- D -glucose and 1- O -methyl-,- D -glucose) and pentoses (D -ribose, D -xylose, D -arabinose and D -lyxose) by Pb2+ ions, was investigated by electrospray ionization and tandem mass spectrometry (MS/MS). Pb2+ ions react mainly with monosaccharides by proton abstraction to generate [Pb(monosaccharide)m , H]+ ions (m = 1,3). At low cone voltage, a less abundant series of doubly charged ions of general formula [Pb(monosaccharide)n]2+ is also observed. The maximum number n of monosaccharides surrounding a single Pb2+ ion depends on the metal : monosaccharide ratio. Our study shows that MS/MS experiments have to be performed to differentiate Pb2+ -coordinated monosaccharides. Upon collision, [Pb(monosaccharide) , H]+ species mainly dissociate according to cross-ring cleavages, leading to the elimination of CnH2nOn neutrals. The various fragmentation processes observed allow the C(1), C(2) and C(4) stereocenters of aldohexoses to be characterized, and also a clear distinction aldoses and fructose. Furthermore, careful analysis of tandem mass spectra also leads to successful aldopentose distinction. Lead cationization combined with MS/MS therefore appears particularly useful to identify underivatized monosaccharides. Copyright © 2002 John Wiley & Sons, Ltd. [source] An HPLC-MS method for simultaneous estimation of ,,, -arteether and its metabolite dihydroartemisinin, in rat plasma for application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 7 2003M. Rajanikanth Abstract This manuscript reports, the development and validation of a sensitive and selective assay method for simultaneous determination of ,,, -arteether and its metabolite dihydroartemisinin (DHA) in rat plasma by liquid chromatography,mass spectrometry. Chromatographic separations were achieved by gradient elution of the analytes with an initial composition of methanol,potassium acetate buffer (pH 4; 73:27, v/v) to 100% methanol in 3 min and maintained for 5 min on a Spheri-10, RP18 (100 × 4.6 mm i.d.) column following an RP18 (30 × 4.6 mm i.d.) guard column. The total ef,uent from the column was split so that one-tenth was injected into the electrospray LC/MS interface. ESI-MS analysis was performed using a Micromass Quattro II Triple Quadrupole Mass Spectrometer equipped with an electrospray source. The MS analysis was carried out at cone voltage of 22 V with a scan range of 200,500 Da. The analytes were quanti,ed from the [M+ K]+ ion chromatograms of ,,, -arteether at m/z 352, DHA at m/z 323, artemisinin at m/z 321 and propyl ether analogue of arteether at m/z 365. Liquid,liquid extractions with a combination of n -hexane and hexane,ethyl acetate (8:2) were used to isolate ,,, -arteether and DHA from rat plasma. The method was validated and gave good accuracy and precision for the studied domain. Linearity in serum was observed over the range 4.375,70 ng/mL for a -arteether and 10,160 ng/mL for , -arteether and DHA. Percentage bias (accuracy) and within- and between-assay precision were well within the acceptable range. This method was applied to study the pharmacokinetics following oral administration of ,,, -arteether (30 mg/kg) in rats. Copyright © 2003 John Wiley & Sons, Ltd. [source] Stability of Anion Binding with Monomers of a Cationic SurfactantCHEMPHYSCHEM, Issue 6 2008Anna Jakubowska Dr. Competitive binding: Electrospray ionisation mass spectrometry is used to probe the binding ability of different anions with a cationic surfactant. Bond strengths are estimated from plots of the intensity of the peak assigned to a given complex ion in the mass spectrum versus the cone voltage applied to induce the abstraction of the counterions from the monomers (see graph). [source] Characterization of the glycosidic linkage of underivatized disaccharides by interaction with Pb2+ ionsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2007Ahlam El Firdoussi Abstract Electrospray ionization in combination with tandem mass spectrometry and lead cationization is used to characterize the linkage position of underivatized disaccharides. Lead(II) ions react mainly with disaccharides by proton abstraction to generate [Pb(disaccharide)m, H]+ ions (m = 1,2). At low cone voltages, an intense series of doubly charged ions of general formula [Pb(disaccharide)n]2+ are also observed. Our study shows that MS/MS experiments have to be performed to differentiate Pb2+ -coordinated disaccharides. Upon collision, [Pb(disaccharide) , H]+ species mainly dissociate according to glycosidic bond cleavage and cross-ring cleavages, leading to the elimination of CnH2nOn neutrals (n = 2,4). The various fragmentation processes allow the position of the glycosidic bond to be unambiguously located. Distinction between glc-glc and glc-fru disaccharides also appears straightforward. Furthermore, for homodimers of D -glucose our data demonstrate that the anomericity of the glycosidic bond can be characterized for the 1 , n linkages (n = 2, 4, 6). Consequently, Pb2+ cationization combined with tandem mass spectrometry appears particularly useful to identify underivatized disaccharides. Copyright © 2007 John Wiley & Sons, Ltd. [source]
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