SORI-CAD

Alternatively, the dissociation process may take place within the FT-ICR cell. For highest efficiency, the ions of interest are subjected to sustained off-reso-nance irradiation immediately prior to the gas collisions (SORI-CAD). 

Figure 1 Comparison of parts of the SORI-CAD ESI FT-ICR mass spectra of the [M + 3 H] + precursor ions of (A) nisin A (wild-type nisin), (B) nisin S5A, (C) nisin H27 K, and (D) nisin I30W-H, showing the region containing doubly charged fragment ions. The ions in the transgenic variants that are shifted in mass compared to nisin A are marked with asterisks. (Reprinted from Lavanant H, Heck A, Derrick PJ, et al. (1998) Characterization of genetically modified nisin molecules by Fourier transform ion cyclotron resonance mass spectrometry. European IVIass Spectrometry 4-. 405-416, with permission IM Publications.)...

IRMPD has a few advantages over SORI-CAD for tandem mass spectrometry in FTMS. First, the use of a collision gas is not necessary in IRMPD MS/MS this maintains optimal pressure in the analyzer cell and eliminates pumpdown time, facilitating its use for on-line... 

HPLC MS/MS. Unlike SORI-CAD, there is no issue with blind spots in the IRMPD product ion spectrum. However, product ions produced on-axis may also absorb the IR radiation to produce secondary fragments. Care must be taken when performing IRMPD to eliminate or minimize the formation of secondary product ions, which are of lower analytical utility than the primary products. This requires that the duration of the event be selected so that no more than half of the precursor ions undergo fragmentation. In contrast with SORI-CAD, 100% of the precursor ions can be converted into products. 

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