The renaissance of desorption chemical ionization mass spectro- metry: characterization of large involatile molecules and nonpolar polymers Marco Vincenti Dipartimento di Chimica Analitica, Universita ` di Torino, Via Pietro Giuria, 5 - 10125 Torino, Italy Received 2 May 2001; accepted 6 July 2001 Abstract The present overview (1) presents a short historical perspective of desorption chemical ionization (DCI), (2) discusses the effect of the changes of some important experimental parameters, revealing which conditions minimize the occurrence of pyrolytic processes, (3) identifies the range of analytical problems where, in our own experience, DCI is more likely to provide unique performance, (4) outlines a possible mechanism for the overall DCI mass spectrometry (DCI-MS) analysis of large nonpolar molecules, and (5) presents several successful applications of DCI-MS, taken from our previous and recent research. (Int J Mass Spectrom 212 (2001) 505–518) © 2001 Elsevier Science B.V. Keywords: Desorption chemical ionization; Direct chemical ionization; Polymers; Molecular receptors; Organometallic compounds 1. Introduction The title is provocative. Actually, no renaissance of desorption chemical ionization mass spectrometry (DCI-MS) is under way. Instead, this interesting technique was abandoned and forgotten even before it was fully developed and understood. The lacking comprehension of the processes involved in DCI is testified by both early and recent literature which called the technique with a variety of different names to stress specific devices used or supposedly predom- inant mechanisms for ion formation, including “direct CI,” “direct exposure CI,” “in-beam CI,” and “surface ionization.” The consecutive introduction and success of fast atom bombardment (FAB), matrix-assisted laser des- orption (MALDI), atmospheric-pressure chemical ionization (APCI), and electrospray ionization (ESI), which progressively drew the attention of mass spec- troscopists, explains only in part the early oblivion of DCI. In my opinion, a more subtle reason for this lack of interest is that the DCI technique appears much simpler than it actually is. The consequence of this apparent simplicity is that most mass spectroscopists utilized DCI seldom and without optimizing the experimental conditions, which in turn produced poor results and a generalized mistrust. On the other hand, the frequent occurrence of plain chemical ionization processes and the uncomplicated apparatus required * Corresponding author. E-mail: vincenti@ch.unito.it Dedicated to R. Graham Cooks on the occasion of his sixtieth birthday. 1387-3806/01/$20.00 © 2001 Elsevier Science B.V. All rights reserved PII S1387-3806(01)00492-4 International Journal of Mass Spectrometry 212 (2001) 505–518 www.elsevier.com/locate/ijms