Collision-induced Decay CID

The lithium-controlled hierarchical assanbly of the helicates, the monomer-dimer equilibrium, and the dynamic processes can be investigated as crystals or in solution. Gas phase studies can be performed by electrospray ionization mass spectrometry (ESI MS). The measurements help explain the solution behaviors of the compounds. However, gas phase reactivity can be studied as well by collision-induced decay (CID) experiments. ESI MS revealed the following findings. 

Because the soft ionization methods used for oligosaccharides produce few fragments, collision-induced dissociation (CID) or post-source decay (PSD) must be used for structural study. These two techniques have been applied to deprotonated, protonated or alkaliated... 

Several desorphon and spray ionization methods can be used to convert S5mthehc polymers into intact molecular or quasimolecular ions (vide supra), whose exact m/z ratio identifies the composition of the polymer. For structural informahon about the polymer, the dissociation behavior or ion-molecule reactions of the polymer ions must be studied. Such reactions, which rarely take place during the soft ionization processes necessary to generate intact gas phase ions from synthetic macromolecules, are most conveniently assessed by tandem mass spectrometry (MS/MS). With MS/MS, a specific precursor ion is mass-selected, so that its reactivity can be investigated without perturbation from the other ions formed upon ionization. The reaction products of this ion are then mass-analyzed and collected in the MS/MS spectrum. MS/MS studies on polymer ions have so far focused on their spontaneous ("metastable") or collision-induced fragmentation. The fragments arising in these reactions are displayed in metastable ion (MI) or collisionally activated dissociation (CAD) spectra, respectively. Customarily, MI spectra acquired with a TOF mass analyzer have been named "postsource decay (PSD)" spectra similarly, CAD is often referred to as CID (collision-induced dissociation). ... 

The loss of 44 5 uma was also observed in the mass spectrum of poly-BFl synthesized by anionic polymerization with PhLi as the initiator (Fig. 39), recorded using the dithranol as matrix. In this case, the difference between the two most intense peaks belonging to each cluster is about 77 Da, suggesting that the most intense peaks correspond to the macromolecular chains terminated with a phenyl group (Ph) at one end, as expected since PhLi was used as initiator [23]. Since very similar mass spectra were recorded using other matrices, such as CHCA (a-cyano-4-hydroxycinnamic acid), DCTB [tra/25-2-[3-(4-t rt-butylphenyl)-2-methyl-2-pro-penylidene]malononitrile], and HABA [2-(4-hydroxylphenylazo)benzoic acid], the question about the loss of a compound with a mass 44 5 requires appropriate investigations by means of post-source decay (PSD) and CID (collision induced dissociation) MALDI-TOF/TOF tandem mass spectrometry methods. 

---