Deuterium isotope exchange mass spectrometry

Infrared Spectrophotometry. The isotope effect on the vibrational spectmm of D2O makes infrared spectrophotometry the method of choice for deuterium analysis. It is as rapid as mass spectrometry, does not suffer from memory effects, and requites less expensive laboratory equipment. Measurement at either the O—H fundamental vibration at 2.94 p.m (O—H) or 3.82 p.m (O—D) can be used. This method is equally appticable to low concentrations of D2O in H2O, or the reverse (86,87). Absorption in the near infrared can also be used (88,89) and this procedure is particularly useful (see Infrared and raman spectroscopy Spectroscopy). The D/H ratio in the nonexchangeable positions in organic compounds can be determined by a combination of exchange and spectrophotometric methods (90). 

Hydrogen-deuterium exchange experiments have been used extensively to study both structural parameters and dynamic and mechanistic aspects. They are utilized in conjunction with both NMR and IR studies. Mass spectrometry, with its high sensitivity and resolution, is ideally suited for isotopic exchange studies. 

With the development of liquid scintillation counters which permit tracer levels of tritium to be measured accurately, isotope exchange reactions are now usually carried out with tritium rather than deuterium. Frequently, however, it is useful to compare rates of exchange for all three isotopes and deuterium exchange may be followed using, for example, mass spectrometry [22]. An example of the application of isotope exchange to proton transfer from carbon is shown in eqns. (8) and (9) for the hydroxide ion catalysed exchange of phenylacetylene in aqueous solution [23], viz. 

Mass spectrometry is an ensemble averaging technique, where data from multiple individual pro-tein/peptide molecules in the gas phase are averaged to give a final mass spectral envelope. This characteristic envelope reflects the natural abundance of heavy isotopes, mostly carbon ( C) and nitrogen C N). In hydrogen exchange experiments, deuterium labeling leads to an increase in mass... 

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