Collision-activation

Collision-activated dissociation (CAD) The same process as collision-induced dissociation (CID). 

By CH4-chemical ionization two predominant ions from DDS were formed in the ion source m/z 163 (M + 1) and m/z 165 (M + 3), which were accelerated and separated in the first quadrupole. Decomposition by collision activation with argon then occurred in the second quadrupole and the resulting daughter ions were separated in the third quadrupole to give rise to collision-induced spectra (equations 41-43). When carrying out the analysis with a solid inlet MS-MS system (TSQ) it was observed that, when operating TSQ in the multiple ion detection mode and selecting the ions m/z 63, 83, 85,99 and 101, only in the third quadrupole was there no interference from other m/z 163 and 165 precursor ions . ... 

J. Shen and A. S. Al-Saeed. Study of oil field chemicals by combined field desorption/collision-activated dissociation mass spectrometry via linked scan. Ana/y Chem, 62(2) 116-120, 1990. 

Figure 7. Cl MS (CH, 150 °C) generated (M+l)+ ion was quadra-pole selected and subjected to collision activated decomposition (N2) to give the mass spectrum (6).

Tandem MS (DFS equipped with EI/F1/FD source) in conjunction with off-line direct inlet HPLC-UV was used for separation and quantification of isomeric antioxidants, C22H30O2S (MW 358 Scheme 6.3), as antioxidants in THF extracts of surgeons gloves [232]. Collision activation MS enabled differentiation between the three isomeric structures (Fig. 6.20). Quantification was achieved by chromatographic analysis of the isomeric species, which are not distinguishable by MS. On-line LC-MS facilitates this kind of analysis. 

Using tandem MS (DFS with EI/FPFD source), electron impact and collision activation mass spectra of a THF extract of an orthopaedic polymer bandage identified IV-isopropyl-A/ -phcnyl-p-phenylenediamine (IPPD, m/z 226) as a cause for contact dermatitis [232]. Fl-MS of the extract of surgeons gloves indicated thio-bis (t-butylcresol) (m/z 358 343, after CID). 

Figure 6.20 Collision activation mass spectra of the El induced molecular ions m/z 358 of 2,2 -thio-bis-(4-methyl-6-t-butylphenol) (1), 4,4 -thio-bis-(6-t-butyl-o-cresol) (2) and 4,4 -thio-bis-(6-t-butyl-m-cresol) (3) (see Scheme 6.3). After Egsgaard et al. [232]. Reprinted from Trends in Analytical Chemistry, 11, H. Egsgaard et al., 164-168, Copyright (1992), with permission from Elsevier...

Diarylfuroxans were found to give diarylacetylenes upon irradiation at 254 nm (Equation 9, Table 2). Cyclobutaphenanthrenes were also obtained when reaction was carried out in the presence of alkenes (Equation 10). The acetylenic derivative is supposed to arise by loss of (NO)2 from a diazete-iV,iV-dioxide. Unimolecular and collision-activated dissociation studies by tandem mass spectrometry also support the loss of (NO)2 from diarylfuroxans molecular ions <1997T17407>. 

DGE a AC AMS APCI API AP-MALDI APPI ASAP BIRD c CAD CE CF CF-FAB Cl CID cw CZE Da DAPCI DART DC DE DESI DIOS DTIMS EC ECD El ELDI EM ESI ETD eV f FAB FAIMS FD FI FT FTICR two-dimensional gel electrophoresis atto, 10 18 alternating current accelerator mass spectrometry atmospheric pressure chemical ionization atmospheric pressure ionization atmospheric pressure matrix-assisted laser desorption/ionization atmospheric pressure photoionization atmospheric-pressure solids analysis probe blackbody infrared radiative dissociation centi, 10-2 collision-activated dissociation capillary electrophoresis continuous flow continuous flow fast atom bombardment chemical ionization collision-induced dissociation continuous wave capillary zone electrophoresis dalton desorption atmospheric pressure chemical ionization direct analysis in real time direct current delayed extraction desorption electrospray ionization desorption/ionization on silicon drift tube ion mobility spectrometry electrochromatography electron capture dissociation electron ionization electrospray-assisted laser desorption/ionization electron multiplier electrospray ionization electron transfer dissociation electron volt femto, 1CT15 fast atom bombardment field asymmetric waveform ion mobility spectrometry field desorption field ionization Fourier transform Fourier transform ion cyclotron resonance... 

Various instruments allow working in special regimes to detect only metastable ions (MI spectra). The conditions of experiments in this case are the same as for the MS/MS experiments, but without collision activation. Any sort of spectrum (daughter ions, parent ions, constant neutral losses) may be generated this way. These spectra are used to establish the pathways of fragmentation, to resolve structural problems. However, the abundance of the metastable signals and even their presence or absence in the spectrum depends on the energy of the parent ions. Therefore, in contrast to CID (see Chapter 3) spectra the difference in MI spectra of two parent ions does not confirm their different structures. 

At first glance the necessity to use collision activation or metastable ion spectra is less evident. However, these two methods allow, first of all, recording pure mass spectra,... 

The dissociation of gas-phase ions can be a guide to the structure of the ions. There are two ways to dissociate gas-phase ions, either by collision-induced dissociation (CID) sometimes termed collision-activation dissociation (CAD) or by photodissociation. In each method, a mass selected ion is dissociated and the fragment ion (often called a daughter ion) is measured the neutral fragment cannot be experimentally observed. 

CAD Collision-activated dissociation CID Collision-induced dissociation... 

Wentrup et al. demonstrated the formation of imidoylketene (1214), methyleneketene (1215), and ethynamine (1216) during the flash vacuum pyrolysis (10-5 torr) of isopropylidene aminomethylenemalonate by collision activation mass spectroscopy and 1R spectroscopy (88JA1337). The imidoylketene (1214) appeared first at a pyrolysis temperature of 390°C. As the temperature was increased, the imidoylketene (1214) was rapidly converted into methyleneketene (1215). The formation of ethynamine (1216) was prominent in the temperature range 680-740°C, and it was accompanied by a sharp decrease in the signal of methyleneketene (1215), whereas the imidoylketene (1214) was less affected. Compounds 1214-1216 were stable at -196°C, but they polymerized on warm-up. 

During the last decade knowledge of the ion chemistry of nitro compounds in the gas phase has increased significantly, partly due to the more widespread use of specialized techniques. Thus various ionization methods, in particular electron impact ionization and chemical ionization, have been used extensively. In addition, structure investigations as well as studies on fragmentation pathways have involved metastable ion dissociations, collision activation and neutralization/reionization studies, supplementary to studies carried out in order to disclose the associated reaction energetics and reaction dynamics. In general, the application of stable isotopes plays a crucial role in the in-depth elucidation of the reaction mechanisms. 

The NRMS technique has been used to distinguish between ion structures, which by other means are not distinguishable, i.e. in situations where fast isomerization takes place after collision activation, but prior to fragmentation5. Thus, NRMS experiments have been used to disclose, e.g., the site of protonation of nitroarenes22. 

The alkene loss from ionized cycloalkyl-substituted nitrobenzenes has been studied by isotopic labelling and collision activation mass spectrometry77. The reaction path was found to depend highly on the placement of the nitro group. The ortho nitro-substituted phenylcyclopropane and its isotopomers were studied. 

It appeared that, exclusively, the methylene hydrogens of the cyclopropane are involved in the ethylene formation77. The product ion, [M — C2H4]+, was by collision activation MS found to be perfectly identical with that of the molecular ion of [2,l]-benzisoxazoline-3-one77 see Scheme 8. 

Another classical case with respect to ort/zo-effects is found for 2-nitrostyrene78. The conceivable regio- and stereo-specifically labelled 2-nitrostyrenes have, in addition to the ring-labelled isotopomer, been studied by collision activation mass spectrometry79. Undoubtedly, the most striking result was the nearly equal contribution of both (in the neutral molecule diastereotopic) hydrogens of the fi-carbon. 

In addition, a series of dinitroaromatic compounds has been studied by collision activation MS95. Strong effects due to competitive processes were noted95. 

Electron impact induced fragmentation of 2-nitrodiarylamines has been studied. An important path is the annelation to carbazoles, as illustrated by the fragmentation of 2-phenylamino-3-nitropyridine103 see Scheme 33. The identity of the product ions was confirmed by collision activation MS upon comparison with authentic samples103. 

Negative atmospheric pressure chemical ionization (APC) low-energy collision activation mss spectrometry has also been employed for the characterization of flavonoids in extracts of fresh herbs. Besides the separation, quantitative determination and identification of flavonoids, the objective of the study was the comparison of the efficacy of the various detection systems in the analysis of flavonoids in herb extracts. Freeze-dried herbs (0.5g of chives, cress, dill, lovage, mint, oregano, parsley, rosemary, tarragon and thyme) were ground and extracted with 20 ml of 62.5 per cent aqueous methanol. After sedimentation the suspension was filtered and used for HPLC analyses. Separations were carried out in an... 

U. Justesen, Negative atmospheric pressure chemical ionisation low-energy collision activation mass spectrometry for the characterisation of flavonoids in extracts of fresh herbs. J. Chromatogr. A 902 (2000) 369-379. 

Synonymous terms used Collisional activation (CA) and collision-activated dissociation (CAD). 

When an automobile collision activates an air bag, sodium azide, NaN3(g), decomposes to form sodium, Na(s), and nitrogen gas, N2(g). (The gas inflates the bag.) This chemical reaction occurs almost instantaneously. It inflates the air bag quickly enough to cushion a driver s impact in a collision. 

Hunt, D.F. Shabanowitz, J. Giordani, A.B. Collision Activated Decompositions in Mixture Analysis With a Triple Quadrupole Mass Spectrometer. Anal Chem. 1980, 52, 386-390. 

Hashimoto, Y. Hasegawa, H. Yoshi-nari, K. Collision-Activated Infrared Multiphoton Dissociation in a Quadrapole Ion Trap Mass Spectrometer. Anal. Chem. 2003, 75,420-425. 

Gauthier, J.W. Trautman, T.R. Jacobson, D.B. Sustained Off-Resonance Irradiation for Collision-Activated Dissociation Involving FT-ICR-MS. CID Technique That Emulates Infrared Multiphoton Dissociation. Anal. Chim. Acta 1991,246,211-225. 

Smith, R.D. Loo, J.A. Baiinaga, C.J. Edmonds, C.G. Udseth, H.R. Colhsional Activation and Collision-Activated Dissociation of Large Multiply Charged Polypeptides and Proteins Produced hy ESI. J. Am. Soc. Mass Spectrom. 1990,1, 53-65. 

---