Comparison of retention indices of some explosives and related compounds calculated by different mathematical methods in reversed-phase liquid chromatography

In reversed phase liquid chromatography, the retention indices of some neutral and acidic explosives and related compounds (nitramines, nitroaromatics, aminoaromatics, and nitrophenols) based on the alkan-2-one, alkyl aryl ketone, and 1-nitroalkane retention index standards hare been determined by the application of a new mathematical adaptation method, viz. a multiparametric least-squares regression iterative method. This method was applied to two types of columns, The first group includes six octadecyl-C-18 columns with different packing materials and obtained from different manufacturers, while the second group comprises one octyl-C-8 column. The retention indices have been extensively studied using either methanol-water or methanol-phosphate buffer mobile phase systems. The calculated multiparametric retention indices values were compared with those obtained by Guardino's, Grobler's, and Kovats' methods. The influences of the concentration of the organic modifier in the mobile phase, aqueous mobile phase pH, and the column packing material on the retention indices of the explosives were also investigated. Good agreement was observed between the retention indices calculated by the use of the four mathematical methods for both neutral and acidic explosives.