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 15mM alpha-hydroxyisobutyric acid (HIBA) as the buffer, 6mM imidazole as the cation chromophore, 3mM 1,3,6-naphthalenetrisulfonic acid (NTS) as the anion chromophore, 4mM 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 5ppm for anions and from 10 to 15ppm for cations with a total run time of under 7min. 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.