Desorption chemical ionisation mass spectrometry

Vincenti and co-workers [241] used desorption chemical ionisation mass spectrometry to determine MWD in PS, PEG, polysiloxanes, and polynorbornene. 

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The nature of refractory methylarsenic compounds in estuary waters has been examined by desorption chemical ionisation mass spectrometry, and mass spectrometry [18]. 

Whilst on-line desorption chemical ionisation mass spectrometry (MS) has been used to analyse fermentation biosuspensions for flavones [11], the majority of MS applications during fermentations have been for the analysis of gases and volatiles produced over the reactor [12-15], or by employing a membrane inlet probe for volatile compounds dissolved in the biosuspensions [16-22]. It is obvious that more worthwhile information would be gained by measuring the non-volatile components of fermentation biosuspensions, particularly when the product itself is non-volatile, which is usually the case. 

Mares, P., Rezanka, T. and Novak, M. (1991) Analysis of human blood plasma triacylglycerols using capillary gas chromatography, silver ion thin-layer chromatographic fractionation and desorption chemical ionisation mass spectrometry. J. Chromatogr., 542, 145-59. 

Microprobe laser desorption laser ionisation mass spectrometry (/xL2MS) is used to provide spatial resolution and identification of organic molecules across a meteorite sample. Tracking the chemical composition across the surface of the meteorite requires a full mass spectrum to be measured every 10 p,m across the surface. The molecules must be desorbed from the surface with minimal disruption to their chemical structure to prevent fragmentation so that the mass spectrum consists principally of parent ions. Ideally, the conventional electron bombardment ionisation technique can be replaced with an ionisation that is selective to the carbonaceous species of interest to simplify the mass spectrum. Most information will be obtained if small samples are used so that sensitivity levels should be lower than attomolar (10—18 M) fewer than 1000 molecules can be detected and above all it must be certain that the molecules came from the sample and are not introduced by the instrument itself. 

Desorption chemical ionisation (DCI) mass spectrometry has been used for detecting additives extracted from polymers [51,52] by a solvent as volatile as possible. To use the DCI probe, 1 -2 iL of the sample, in solution, are applied to the probe tip, composed of a small platinum coil, and after the solvent has been allowed to evaporate at room temperature, the probe is inserted into the source. The sample is then subject to fast temperature ramping. DCI does not seem to be the most suitable mass-spectrometric method for analysis of dissolved polymer/additive matrices, because ... 

Montaudo, G., Montaudo, M. S., Puglisi, C., Samperi, F., and Sepulchre, M., End-group Gharacterization of Poly(methylphenylsilane) by Alkali Metal Salts Doped MALDI-TOE Mass Spectra, Macromol. Chem. Phys., 197, 2615,1996. Weidner, St. and Kiihn, G., Chemical End-group Derivatization of Polyfethyl-eneglycol)-Investigation by Matrix-assisted Laser Desorption/Ionisation Mass Spectrometry, Rapid Comm. Mass. Spectrom., 10, 942,1996. 

Spanos, G. A., Schwartz, S. J., van Breemen, R. B. and Huang, C.-H. (1995) High performance liquid chromatography with light scattering detection and desorption chemical ionisation tandem mass spectrometry of milk fat triacylglycerols. Lipids, 30, 85-90. 

Fast atom bombardment (FAB) Plasma desorption (PD) Liquid secondary-ion mass spectrometry (LSIMS) Thermospray (TSP)/plasmaspray (PSP) Electrohydrodynamic ionisation (EHI) Multiphoton ionisation (MPI) Atmospheric pressure chemical ionisation (APCI) Electrospray ionisation (ESI) Ion spray (ISP) Matrix-assisted laser desorption/ionisation (MALDI) Atmospheric pressure photoionisation (APPI) Triple quadrupole (QQQ) Four sector (EBEB) Hybrid (EBQQ) Hybrid (EB-ToF, Q-ToF) Tandem ToF-ToF Photomultiplier... 

Several years later, the next step in the application of MS-MS for mixture analysis was developed by Hunt et al. [3-5] who described a master scheme for the direct analysis of organic compounds in environmental samples using soft chemical ionisation (Cl) to perform product, parent and neutral loss MS-MS experiments for identification [6,7]. The breakthrough in LC-MS was the development of soft ionisation techniques, e.g. desorption ionisation (continuous flow-fast atom bombardment (CF-FAB), secondary ion mass spectrometry (SIMS) or laser desorption (LD)), and nebulisation ionisation techniques such as thermospray ionisation (TSI), and atmospheric pressure ionisation (API) techniques such as atmospheric pressure chemical ionisation (APCI), and electrospray ionisation (ESI). 

Rather limited use has been made of mass spectrometry in the study of organotin compounds,23-24 though MS linked to gas-liquid chromatography is now being used for the identification of organotin compounds, particularly in environmental studies. Most of the early work involved electron ionisation (El), but in recent years, other techniques such as chemical ionisation (Cl),25 fast atom bombardment (FAB),26, 27 field desorption,28 surface ionisation,29 and, particularly, electrospray (ES),30 31 have been used. 

Mass spectroscopy [electron ionisation (El), chemical ionisation (Cl), electrospray ionisation (ESI), fast atom bombardment (FAB), matrix-associated laser desorption ionisation (MALDI), inductively coupled plasma-mass spectrometry (ICP-MS)... 

Lattimer and co-workers [25] have applied mass spectrometry (MS) to the determination of antioxidants and antiozonants in rubber vulcanisates. Direct thermal desorption was used with three different ionisation methods [electron impact (El), chemical ionisation (Cl), field ionisation (FI)]. The vulcanisates were also examined by direct fast atom bombardment mass spectrometry (FAB-MS) as a means for surface desorption/ionisation. Rubber extracts were examined directly by these four ionisation methods. Of the various vaporisation/ionisation methods, it appears that field ionisation is the most efficient for identifying organic additives in the rubber vulcanisates. Other ionisation methods may be required, however, for detection of specific types of additives. There was no clear advantage for direct analysis as compared to extract analysis. Antiozonants examined include aromatic amines and a hindered bisphenol. These compounds could be identified quite readily by either extraction or direct analysis and by use of any vaporisation/ionisation method. 

The different stages of the preparation of peptide surfaces can be confirmed with surface-sensitive physical and chemical analysis techniqnes. For gold-based SAMs, Mrksich and co-workers have introduced a matrix-assisted laser desorption ionisation time-of-ftight (MALDI-TOF) mass spectrometry-based analysis procedure with which they are able to identify the presence of various surface functional groups via their mass (Yeo Mrksich, 2006 Yeo et al., 2003). Although this method is applicable to SAMs, it is not strictly a surface sensitive technique, as the desorption process in MALDI is not confined to the uppermost layer of a material. 

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