CID procedure

The FIA-MS screening approach using soft ionisation interfaces prior to any CID procedure provides an overview of the MS separation procedure, which is based on the different m/z ratios of the molecular or cluster ions generated. With the help of this very fast screening method—positive or negative FIA-MS by-passing the analytical column—the surfactant chemist is able to characterise complex blends and formulations without difficulty (Fig. 2.5.1) while the experienced analyst is able to make initial statements about the presence of frequently used and therefore most important surfactants in environmental samples (Fig. 2.5.2) despite the presence of complex matrices. The information provided by ESI or APCI—FIA—MS overview spectra for a first characterisation [8,17-19], which were also available with non-API soft ionising interfaces such as FAB [20] or TSI [9] in industrial blends as well as environmental samples, were obtained from ... 

F.W. McLAFFERTY [38] and K.R. JENNINGS [39] introduce the collision-induced dissociation (CID) procedure. 

The CID procedure causes more or less random peptide bond cleavage. Therefore, a number of fragments are obtained that differ by a single amino acid residue. Several types of fragments are produced, and their nomenclature is shown in Figure 15.13. 

Modem mass spectrometric methods greatly help to speed up degradation studies by identifying the molecular mass of peptide fragments. Various desorption techniques, which produce protonated protein ions in the gas phase, are applied. Prominent examples are fast-atom bombardment (FAB) and matrix- assisted laser desorption/ionization (MALDI). Most commonly these techniques provide only the mass of the molecular ion, but they can be coupled with a collision-induced dissociation (CID) procedure. The ions are activated by collisions with neutral target gases, and the peptides dissociate in the gas phase. The resulting mass spectra... 

If fragmentation of the analyte molecules is desired, it can be caused by collision-induced dissociation (CID, Section 24.5E). In this case, tandem mass spectrometry is necessary because the first mass analyzer in the system is used to select fragments of the peptide from CID based on their overall mass, while the second mass analyzer in the system records the spectrum of the selected peptide fragment. Multiple fragments from the CID procedure can be analyzed this way. The final spectrum for each peptide fragment selected has the typical appearance of a family of ions, as shown below. 

Now that a procedure for establishing the corresponding composition scales for the rich lean pairs of stream has been outlined, it is possible to develop the CID. The CID is ccHistructed in a manner similar to that described in Chapter Five. However, it should be noted that the conversion among the corresponding composition scales may be more laborious due to the nonlinearity of equilibrium relations. Furthermore, a lean scale, xj, represents all forms (physically dissolved and chemically combined) of the pollutant. First, a composition scale, y, for component A in... 

Using this procedure, D- and L-a-amino acids have been enantiodifferentiated in the gas phase. ESI of hydroalcoholic solutions of the amino acid and CUCI2 into the source of an ion trap mass spectrometer reveals the presence of singly charged, covalently bound dimeric and trimeric ions. Table 10 reports the CID results of the diastereomeric complexes [A/ -Cu -(ref)2-H] and [As-Cu (ref)2-H]. ... 

The diastereomeric mixture of l,3,4,6,7,lll>hexahydro-2/T-pyrazino LI, 2-bj isoqu inoline-1,4-d iones 497 was prepared in four-component Ugi/ Pictet-Spengler two-step procedure when aldehydes/ketones, a-ketoa-cids, 2-(3,4-dimethoxyphenyl)ethyl isocyanide and primary amines were stirred in MeOH, and then the evaporated reaction mixture in TFA (07SL500). 

Perez-Cid et al. (1996) compared Tessier and BCR sequential extractions for the speciation of Cu, Cr, Pb, Ni and Zn in sludge from an urban wastewater treatment plant and found similar performance for the two procedures. Zufiaurre et al. (1998) later demonstrated, using the Tessier method and PCA, that, since most metals in a sludge were bound to oxidisable and residual fractions, bioavailability was likely to be very low. 

The development of procedures for the identification of CW agents in biomedical samples is ongoing and existing procedures are continuously improved. Quantization is also an important factor, and an isotope dilution GC/MS/MS method was developed for the quantitative determination of five organophosphorus acids derived from the nerve agents VX, tabun, sarin, soman, and cyclohexyl sarin in urine samples. The acids were isolated and converted into their methyl esters by diazomethane. Detection limits in the low p,g I. 1 were obtained using CID of the protonated molecular ion peaks obtained with isobutane Cl(58). 

Siegenthaler (34) reported a screening procedure for phosphonic acids, which included ethyl methyl-phosphonothioic acid and ethyl isopropylphospho-nothioic acid, based on negative ion ESI under conditions that promoted in-source CID. LC separation was on a 250 x 3mm C18 column, eluted with a water-methanol-20 mM NH4OAc gradient,... 

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