|
| ||
|
|
||
Breakdown Curves (breakdown + curve)
Selected AbstractsEnergy-resolved in-source collisionally induced dissociation for the evaluation of the relative stability of noncovalent complexes in the gas phaseRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2005Nataliya Lyapchenko Energy-resolved in-source collisionally induced dissociation (CID) studies on the complexation of alkali metal cations by some crown ethers, nucleic acid bases, and amino acids have been performed. It has been shown that the cone voltage corresponding to the maximum ion abundance (Vc,Imax) of the breakdown curve is characteristic of a given ion and not influenced by the cone desolvation process or the composition of the solution. Very good agreement of the Vc,Imax value with the bond strength of the ion has been observed. Determination of the Vc,Imax values for different ionic species is a useful, simple, and inexpensive way to obtain their relative stabilities in in-source CID conditions. Copyright © 2005 John Wiley & Sons, Ltd. [source] Influence of differently ionized species on fragmentation pathways and energetics of a potential adenosine receptor antagonist using a triple quadrupole and a multistage LTQ-OrbitrapÔ FTMS instrumentJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2009Wendy Zhong A systematic study was conducted to investigate the influence of differently ionized species on the fragmentation pathways and energetics of a piperazine-containing adenosine by using different cations or anions. Very different fragmentation mechanisms were observed in protonated- versus sodiated-molecules, which indicated that the proton is mobilized to promote the charge-direct fragmentation, whereas Na+ cation was fixed at the heterotricyclic ring structure provoking charge-remote fragment ions. This finding was also supported by the results observed in the fragmentation behaviors in the deprotonated-molecule. The energetics of these fragment ions were also explored by using the breakdown curves obtained from the triple quadrupole and LTQ-OrbitrapÔ instrument. The data indicated that the lowest energy pathways in the protonated-molecule [M+H]+ involve breaking a CN bond connecting an ethylene bridge and heterotricyclic ring structure. The lowest energy pathway is the cleavage of a CO bond connecting the methoxy ethyl group and phenolic oxygen to form a distonic radical ion for a sodiated-molecule [M+Na+]and a deprotonated-molecule [M-H],. The data suggest that by choosing the differently ionized species, one can probe different fragmentation channels that can provide additional structure information for an unknown impurity and possibly degradation product identification. In addition, by comparing the data obtained from triple quadrupole and LTQ-Orbitrap instruments, one can develop further understanding of the differences in the fragmentation behaviors due to the variations in the collision activation-dissociation process. From the side-by-side comparison with the breakdown curves obtained for both instruments, the difference in fragmentation behaviors caused by the difference in dissociation processes that occur in these two types of instruments can be probed. J. Heterocyclic Chem., (2009). [source] Tuning compounds for electrospray ionization/in-source collision-induced dissociation and mass spectra library searchingJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2001Wolfgang Weinmann Abstract Tuning compounds for positive and negative electrospray ionization (ESI) were tested for the tuning of in-source collision-induced dissociation (ESI/CID) with three types of SCIEX API instruments (API 365, 2000 and 3000) in the single-quadrupole mode. The vacuum interfaces of these instruments differ slightly in geometry, but the principles of ionization and solvent evaporation by nebulizer and curtain gases, orifice and skimmer are identical. For comparison of in-source CID, breakdown curves of haloperidol, paracetamol, metronidazole and metamizole were acquired by increasing the orifice voltages. The API 2000 and 3000 required higher orifice voltages than did the API 365 to induce a similar degree of fragmentation of the protonated or deprotonated molecules to characteristic fragment ions. This increase of orifice voltage could be demonstrated with each of the four compounds tested by a shift of the maxima of the breakdown curves to higher orifice voltages. A procedure with three collision energy (CE) levels for drug identification with a mass spectra library set up with an API 365 therefore required an adjustment of the orifice voltages to higher values when being transferred to an API 2000 or API 3000. The corresponding orifice voltages for the three instruments were 20/50/80 V (API 365), 30/90/130 V (API 2000) and 40/80/120 V (API 3000). However, a change in orifice voltage of ±10 V (with the API 2000 and 3000) hardly influenced the fit values of a library search for each single CE level. For adjusting orifice voltages with different instruments, a tuning procedure with haloperidol and paracetamol is presented. With this tuning procedure an ESI/CID mass spectra library set up for API 365 and API 150 could also be used for drug identification with an API 2000 and an API 3000 with good library search results. Copyright © 2001 John Wiley & Sons, Ltd. [source] Differentiation of configurations of the phenylbutenoid dimer derivatives from Zingiber cassumunar by tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2009Juanjuan Chen High-performance liquid chromatography/electrospray tandem mass spectrometry was developed to distinguish isomers and compounds of similar structures with different configurations in the rhizomes of Z. cassumunar. Energy-resolved breakdown curves were utilized to differentiate four compounds. Compounds 2 (3R,4S) and 4 (3R,4R) were a pair of stereoisomers which could be distinguished easily by breakdown curves. The breakdown curve of compound 1 was identical to that of compound 2, which suggested that the configuration of compound 1 was (3R,4S) or (3S,4R). The breakdown curve of compound 3 was completely different from those of compounds 1, 2 and 4, and it might be that the configuration of the double bond of compound 3 was different from the other three compounds. Hence, the described method using breakdown curves has great potential in the distinguishing of isomers and compounds of similar structure with different configurations. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||