Plasma desorption ionization

Plasma desorption mass spectrometry utilizes a 252Cf (californium) ionizing source which produces MeV fission fragments. The interaction of the fission fragments with the sample produces ions which are mass analyzed. The samples are applied to a nitrocellulose-coated mylar target, either by droplet or electrospraying, allowed to adsorb, and then washed with a 0.1% trifluoroacetic acid solution. Typically the samples are allowed to air dry prior to being introduced into the mass spectrometer. The sample ions that are formed, are accelerated into a time-of-flight mass spectrometer for mass analysis.

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Figure 5-3. Plasma desorption mass spectra of anthocyanidins extracted from A. chrysanthemum, B. begonia, C. carnation, and D. phlox. The data in this figure was published in the article 'Plasma desorption mass spectrometry of anthocyanidins', Rap. Comm. Mass Spectrom. 7:400-403, by Wood, K. V., Bonham, C. C., Ng, J., Hipskind, J. and Nicholson, R. L. 1993. Copyright John Wiley and Sons. Reproduced with permission.

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Figure 5-3. Plasma desorption mass spectra of anthocyanidins extracted from A. chrysanthemum, B. begonia, C. carnation, and D. phlox. The data in this figure was published in the article 'Plasma desorption mass spectrometry of anthocyanidins', Rap. Comm. Mass Spectrom. 7:400-403, by Wood, K. V., Bonham, C. C., Ng, J., Hipskind, J. and Nicholson, R. L. 1993. Copyright John Wiley and Sons. Reproduced with permission.

Accelerating potentials between 15-20 keV are typically used, with data being collected from anywhere between fifteen minutes to an hour depending on the sample. The useful mass range for PDMS is up to m/z 5000. Typically the observed ion is the protonated molecule. PDMS, however, has proven to be particularly well-suited for the analysis of pre-charged species like anthocyanidins. This can be seen in Figure 5-3, which shows the plasma desorption mass spectrum of anthocyanidins extracted from chrysanthemum, begonia, carnation and phlox (Wood et al., 1993). Note the presence of cyanidin (m/z 287; 1.40), as a dominant ion in the first three mass spectra. Pelargonidin (m/z 271; 1.39) and delphinidin (m/z 303; 1.42) are also observed. The phlox sample analyzed was white phlox which explains the absence of any anthocyanidins.

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