Electrospray ionization tandem mass spectrometric study of salt cluster ions. Part 1— Investigations of alkali metal chloride and sodium salt cluster ions
Article first published online: 24 JAN 2001
Copyright © 2001 John Wiley & Sons, Ltd.
Journal of Mass Spectrometry
Volume 36, Issue 1, pages 79–96, January 2001
How to Cite
Hao, C., March, R. E., Croley, T. R., Smith, J. C. and Rafferty, S. P. (2001), Electrospray ionization tandem mass spectrometric study of salt cluster ions. Part 1— Investigations of alkali metal chloride and sodium salt cluster ions. J. Mass Spectrom., 36: 79–96. doi: 10.1002/jms.107
- Issue published online: 24 JAN 2001
- Article first published online: 24 JAN 2001
- Manuscript Accepted: 1 NOV 2000
- Manuscript Received: 11 MAY 2000
- National Sciences and Engineering Research Council Canada.
- Canada Foundation for Innovation.
- Ontario Research and Development Challenge Fund.
- electrospray ionization;
- collision-induced dissociation;
- salt cluster;
- singly charged ion;
- multiply charged ion
Salt cluster ions of alkali metal chlorides ACl (A = Li+, Na+, K+, Rb+ and Cs+) and sodium salts NaB (B = I−, HCOO−, CH3COO−, NO2−, and NO3−), formed by electrospray ionization, were studied systematically by mass spectrometry. The influences on the total positive ion and negative ion currents of variation of solvent, solution concentration, desolvation temperature, solution flow-rate, capillary voltage and cone voltage were investigated. Only cone voltage was found to influence dramatically the distribution of salt cluster ions in the mass spectra observed. Under conditions of normal cone voltage of ∼70 V, cluster ions having magic numbers of molecules are detected with high relative signal intensity. Under conditions of low cone voltage of ∼10 V, the distribution of cluster ions detected is characterized by a relatively low average mass/charge ratio due to the presence of multiply charged cluster ions; in addition, there is a marked reduction in cluster ions having a magic number of molecules. Product ion mass spectra obtained by tandem mass spectrometry of cluster ions are characterized by a base peak having a magic number of molecules that is less than and closest to the number of molecules in the precursor ion. Structures have been proposed for some dications and some quadruply charged ions.
At pH 3 and 11, the mass spectra of NaCl clusters show the presence of mixed clusters of NaCl with HCl and NaOH, respectively. The effects of ionic radius on 20 distributions of cluster ions for 10 salts were investigated; however, the fine structure of these effects is not readily discerned. Copyright © 2001 John Wiley & Sons, Ltd.