A novel method for analysis of explosives residue by simultaneous detection of anions and cations via capillary zone electrophoresis

A novel electrolyte has been developed for the simultaneous separation of cations and anions in low explosive residue by capillary electrophoresis. This electrolyte contains 15 mM alpha-hydroxyisobutyric acid (HIBA) as the buffer, 6 mM imidazole as the cation chromophore, 3 mM 1,3,6-naphthalenetrisulfonic acid (NTS) as the anion chromophore, 4 mM 18-crown-6 ether as a cation selectivity modifier, and 5 % (v/v) acetonitrile as an organic modifier. The pH was adjusted to 6.5 using tetramethylammonium hydroxide (TMAOH), an electroosmotic flow modifier. The method was optimized by varying the concentrations of alpha-HIBA, imidazole, and 1,3,6-NTS at three different pH values. The results provided a simultaneous indirect photometric analysis of both anions and cations with detection limits ranging from 0.5 to 5 ppm for anions and from 10 to 15 ppm for cations with a total run time of under 7 min. The method was then applied to the analysis of Pyrodex (R) RS and black powder, as well as several smokeless powders. The results obtained were consistent with previously reported results for separate anion and cation analysis and provide a faster, more complete analysis of each sample in a single chromatographic run. (c) 2005 Elsevier B.V. All rights reserved.