Foreword: Collision and reaction cell techniques in atomic mass spectrometry

Collision and reaction cell techniques have been utilized for many years in the study of gas-phase reactions and in organic and biological mass spectrometry, but have only recently been used to advantage in atomic mass spectrometry. The primary problem in both glow-discharge mass spectrometry (GDMS) and inductively coupled plasma mass spectrometry (ICPMS) techniques remains the existence of spectral interferences, and collision/reaction cell methods coupled with ion–molecule chemistry offer a low-cost, flexible, and efficient means for the elimination or avoidance of such interferences. While originally postulated as a means for interference reduction in the late 1980s, serious development and investigation of this approach in the atomic MS field has only taken place in the last 10 years. The recent activity has been spirited, however, as indicated by both publication activity and the development of new generation commercial instrumentation. A cursory examination of publication trends shows a rapid rise in the number of publications over the last decade (see Fig. 1). A variety of collision/reaction cell ICPMS instruments are now available, with several companies offering multiple models equipped with such capability (Table 1). Clearly this is a topical area in the atomic mass spectrometry field. It is accordingly appropriate to review technology developments, highlight uses and applications, and discuss future directions relating to collision and reaction cell techniques. This is the focus of this special issue.

Table 1 List of currently available collision/reaction cell ICPMS instruments

Instrument	Manufacturer	Cell type/characteristic
ELAN DRC-e, DRC II	PE-SCIEX	Quadrupole bandpass reaction cell
Platform, Isoprobe	GV Instruments	Hexapole reaction cell
7500ce, 7500cs	Agilent	Octopole reaction system
X Series	Thermo Electron	Hexapole reaction cell
P-5000	Hitachi (Japan)	Ion trap (Paul type)

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Given the nascent but maturing nature of the technology, and the opportunity to perhaps effect improvement and refinement of techniques at this stage, the guest editors have developed a special issue format that includes Perspectives papers as well as solicited and contributed research papers. The Perspective papers are primarily intended to provide a broad and encompassing view of the field, and to secondarily stimulate new ideas and challenge conventional wisdom presumptions. The first Perspective paper (by the guest editors) provides an assessment of the development of collision/reaction cell techniques and the current status of methods and applications. The next two Perspective papers, those by Armentrout and Gerlich, provide a somewhat orthogonal view of developments in this field. Both workers are experts in topical areas of relevance to ICPMS but are not, in fact, ICPMS practitioners. This is by intent, the guest editors' judgement being that such viewpoints can provide fresh perspective and insight, unencumbered by past work or experiences in the field. Armentrout's Perspective is intended to be an ion–molecule primer to help edify the atomic spectroscopist in the methods, terminology, and application of ion–molecule chemistry. The Perspective of Gerlich provides an overview of multipole devices and cells, along with a description of the ways such cells can be used and employed for traditional and non-traditional applications. Finally, the Marcus Perspective paper reviews the use of purely collisional (non-reactive) techniques in atomic mass spectrometry and begs reflection on the role and future of this approach versus the more recently popular reactive chemistry approach. The accompanying research papers, by various research groups worldwide, present important fundamental, technique, and applications findings and results.

We believe this special issue compilation of papers provides a synopsis of the state of the art for Collision and Reaction Cell Techniques in Atomic Mass Spectrometry. We hope the readers and the atomic mass spectrometry community find this special issue informative and useful.

David W. Koppenaal and Gregory C. Eiden

Pacific Northwest National Laboratory, Richland, WA, USA

Fig. 1 CRC-ICPMS publication history, 1994–2004 (to date). Compiled from ISI Web of Science database.

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