In-source collision-induced dissociation

The on-line coupling of CE with electrospray ionization mass spectrometry (CE-ESI-MS) allows high separation efficiency together with high sensitivity and selectivity as well as molecular structural information. A CE-UV-ESI-MS method was developed for the analysis of hoscyamine, scopolamine, and other tropane derivatives [131]. The differentiation of hyoscyamine from littorine, commonly encountered in plant material, was demonstrated using in-source collision-induced dissociation. The developed method was applied to the analysis of these alkaloids in Belladonna leaf extract and in Datura Candida x D. awreahairy root extract. Recently, CE coupled with electrochemiluminescence detection has been used for the determination of atropine and scopolamine in Flos daturae [132]. 

There are some pairs of isomeric sulfonamides, which cannot be unambiguously identified from these fragments. Discrimination between these isomers can be achieved either by two stages of MS-MS in an ion-trap instmment or by means of a combination of in-source collision-induced dissociation (CID) to generate the compound-specific RNHj and subsequent MS-MS on this ion in a triple-quadmpole instrument [11]. 

Automated data processing, data reduction, spectral interpretation, and reporting are also integral parts of open-access sample analysis. Mallis et al. [33] described the use of an open-access system with e-mail capabilities to distribute processed data reports to the chemist. Several methods have been developed, including structure elucidation with in-source collision-induced dissociation (CID). 

On the other hand, there are limitations to the LC-MS analysis. The two most common ionization techniques available in LC-MS, TSP and electrospray ionization (ESI), yield primarily molecular weight information i.e., little fragmentation is observed to conhrm the structure of the analyte. Thermally induced decomposition " and in-source collision-induced dissociation have been utilized to produce structurally signihcant ions. However, these techniques are often unreliable and can suffer signihcant losses in sensitivity. Alternatively, the on-line photolysis can be used to induce photolytic dissociation of different types of compounds. Volmer et al. have reported the simultaneous detection and conhrmation of several A-nitrosodialkylamines by on-line coupling of a photolysis reactor with an ESI mass spectrometer. 

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. 

In-Source Collision-Induced Dissociation of ESI-Produced Ions Fragmentation of the intact molecular ions can be induced in the ion source by... 

Peptide mapping, in-source collision-induced dissociation, precursor-ion scan, and neutral-loss scan are employed to selectively identify phosphopeptides... 

Figure 5.28 (a) Sketch of the electrospray ion source and MS interface of Aleksandrov et at. 1 metal capillary held at 2-4 kV relative to the first of the two differentially pumped diaphragms (2 and 3) the potential difference between 2 and 3 was varied between 0 and 900 V to study solvent declustering and in-source collision induced dissociation. 4 ion lenses. 5 entrance slit of magnetic sector mass spectrometer. 6 total ion current monitor plate, (b). Mass spectrum of erythromycin obtained using the apparatus shown in (a). Reproduced from Aleksandrov Doklady Phys. Chem. 277, 572 (1985), copyright (1985), with permission from Springer Science and Business Media. 

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