Mass measurements of natural products by solution phase secondary ion mass spectrometry employing silver® and thallium® derivatives1-2

The promotion and detection of molecular ions in the mass spectra of relatively simple to complex biosynthetic products, and a large cross-section of other compounds, has been simplified by employing silver or thallium(I) tetrafluoroborate in sulfolane for solution phase SIMS. The easily recognized isotope doublets of¹⁰⁷Ag, ¹⁰⁹Ag (52:49 natural abundance) and ²⁰³T1 ²⁰⁵T1 (30:70) combined with the generally very strong [M + Ag]⁺ and [M+T1]⁺ molecular ion complex intensities provided powerful new techniques for mass measurements. Because the degree of molecular ion complex intensity was found to be a function of the specimens structure, application of these methods augmented by lithium and/or Nal or trifluoromethanesulfonic acid (for basic nitrogen containing compounds) was recommended for all new molecular weight determinations by mass spectrometry.