Plasma Desorption Mass Spectrometry — Achievements and Frontiers

Almost twenty years ago, R.D. Macfarlane, D.F. Torgerson and others at Texas A&M discovered that fission fragments from a 252Cf source can cause ejection of whole intact molecular ions from a sample consisting of a multi-layer deposit of organic molecules [1]. The secondary ions were mass analyzed with a time-of-flight (TOF) technique. The potential of the new mass spectrometric method, called Plasma Desorption Mass Spectrometry (PDMS) was demonstrated in a number of experiments by the Texas group but it was not until almost ten years later when the full potential for high mass analysis was demonstrated [2,3], in fact almost coinciding with the appearance of the FAB method [4], that the method started to be used more extensively in mass spectrometry applications. In fact the use of adsorption of sample molecules to a substrate of nitrocellulose [5] was probably the singly most important reason why PDMS started to be used as a tool in protein chemistry. In establishing the potential of the method important contributions, in addition to those at Texas A&M university were made by Field and Chait [6] at Rockefeller university and by the Uppsala-Odense collaboration [7]. Already a few years after the Texas discovery groups at Darmstadt [8], Orsay [9], Erlangen [10] and Uppsala [11] started to use accelerators, in addition to 252Cf, to study various aspects of the basic mechanisms involved in PDMS.