Skimmer CID

Example Even a moderate voltage drop between nozzle and skimmer can cause the elimination of weakly bonded substituents such as CO2 in case of carbon dioxide-protected deprotonated A-heterocycles. In particular SnMes-substituted anions such as 2-(trismethylstannyl)pyrrole-A-carbamate exhibit variations in the [A-C02]7A ratio of up to a factor of 30 (Eig. 11.10). [76] 

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Jedrzejewski, P.T. Lehmann, W.D. Detection of Modified Peptides in Enzymatic Digests hy Capillary Liquid Chromatogra-phy/ESI-MS and a Programmable Skimmer CID Acquisition Routine. Anal. Chem. 1997, 69, 294-301. 

McDonald, L. A., Barbieri, L. R., Carter, G. T., Krappa, G., Feng, X., Lotvin, J. A., and Siegel, M. M. (2003). FTMS structure elucidation of natural products Application to muraymycin antibiotics using ESI multi-CHEF SORI-CID FTMS(n), the top-down/bottom-up approach, and HPLC ESI capillary-skimmer CID FTMS. Anal. Chem. 75 2730-2739. 

P.T Jedrezejewski and W. D. Lehmann, Detection of modified peptides in enzyme digests by capillary liquid chromatography/electrospray mass spectrometry and a programmable skimmer CID acquisition routine, A a/. Chem. 69 (1997), 294-301. 

A. Beck, M. Deeg, K. Moeschell, E.K. Schmidt, E.D. Schleicher, W.Voelter, H.U. Haring, R. Lehmann, Alkaline LC-ESI-skimmer-CID-MS for phosphopeptide screening. Rapid Commun. Mass Spectrom., 15 (2001) 2324. 

McDonald,L.A. Barbieri, L.R. Carter, G.T. Knippa, G. Feng, X. Lotvin, J.A. Siegel, M.M. FTMS Structure Elucidation of Natural Products Application to Muraymycin Antibiotics Using ESI Multi-CHEF SORI-CID FTMSn, the Top-Down/Bottom-Up Approach, and HPLC ESI Capillary-Skimmer CID FTMS, Anal. Chem. 75(11), 2730-2739 (2003). 

Smith et al. [26-28] demonstrated that by a further increase of the nozzle-skimmer potential difference the internal energy of the ions can be increased and fragmentation of the multiple-charge protein ions can be induced as a result of colhsion-induced dissociation (CID). This is called in-source CID in this text. 

Electrospray analysis can be performed in positive and negative ionization modes. The polarity of the ions to be analyzed is selected by the capillary voltage bias. A novel feature of the ESI mass spectrum is the formation of intact molecular ions of the analyte. Fragmentation, if desired, can be induced in the ion-transport region of the ESI source by increasing the sampling cone voltage. This process is known as in-source collision-induced dissociation (CID) or nozzle-skimmer (NS) dissociation. 

Several gas-phase fragmentation techniques have found a niche as a possible means to sequence oligonucleotides. These include ESI in-source CID (nozzle-skimmer voltage to induce fragmentation), IRMPD in an FT-ICR MS instrument, MALDI in-source decay and post-source decay, and CID-MS/MS of the ESI-produced ions. CID generates complementary (a — B )- and in-type ions, which can provide bidirectional sequencing from the 5 3 direction and 3 5 ... 

So-called in-source CID occurs in the vicinity of the skimmer cone in API interfaces (e.g. Figure 6.40(b)) where the background pressure is comparable to that in a q collision cell (mtorr range). A potential is normally applied to the skimmer cone to permit gentle collisional activation that leads to stripping of clustered solvent molecules from the analyte ions (see Section 5.3.3a), but by increasing this potential (referred to as the cone potential or skimmer potential ) it is possible to increase the... 

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