Influence of metal ions on the acquisition and quality of 252Cf plasma-desorption mass spectra.

The presence of a few mol per cent of Ca2+ ions considerably modified the 252Cf plasma-desorption mass spectrum of a phosphorylated glycolipid. In the negative-ion mode, increasing amounts of Ca2+ caused gradual disappearance of the spectrum; it was quenched at the molar ratio 3 Ca2+/4 glycolipid. Clusters as big as 5500 were observed at certain ratios of Ca2+/glycolipid. Similar, but less pronounced effects were seen in the positive-ion mode.