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 NaNO3KNO3 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 KNO3NaClO4 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 nth 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 © 2006 John Wiley & Sons, Ltd.