Analysis of oxidizer salt mixtures by electrospray ionization mass spectrometry.

Binary aqueous mixtures of NaNO3, KNO3 and NaClO4 oxidizers were analyzed using electrospray ionization mass spectrometry. Sodium nitrate solutions were observed to form doubly charged clusters of the type [(NaNO3)n2Na]2+ and [(NaNO3)n2NO3]2-, where n = 11, 13, 15, etc., in addition to singly charged cluster ions that have been reported previously. The identity of the doubly charged clusters was determined by tandem mass spectrometry. Two-component NaNO3-KNO3 salt solutions were observed to form cluster ions of the type [(NaNO3)i(KNO3)jNO3]- in the negative ion mode and [(NaNO3)i(KNO3)jNa]+ and [(NaNO3)i(KNO3)jK]+ in the positive ion mode, where i + j = 1, 2, 3 ... 10. Two-component solutions of KNO3-NaClO4 formed ions of the type [(KNO3)i(NaClO4)j(KClO4)k(NaNO3)lK](+) and [(KNO3)i(NaClO4)j(KClO4)k(NaNO3)lNa]+ in the positive ion mode, where i + j + k + l = 1, 2, 3 ... 10. Similar clusters containing excess nitrate and perchlorate to provide the charge are formed in the negative ion mode. In each case, the maximum number of spectral lines for a cluster of size n can be calculated as the number of combinations of n(th) order (where n = i + j) of N different cation-anion pairs taken with replication and without regard for the ordering of the N cation-anion pairs. The actual number of lines observed may be reduced due to degeneracy of nominal m/z values for some ions. Copyright (c) 2005 John Wiley & Sons, Ltd.