Novel electrolyte for the analysis of cations in low explosive residue by capillary electrophoresis

A novel electrolyte has been developed for the effective separation by capillary electrophoresis of cations detected in low explosive residue. This electrolyte, with a pH of 4.4, employs 17.5 mM alpha-hydroxyisobutyric acid (HIBA) as the complexing agent, 6 mM imidazole as the ultraviolet visualization agent, 4 mM 18-crown-6 ether as a modifier to enhance the selectivity of the inorganic cations, and 5% (v/v) acetonitrile as an organic additive. Studies which assessed the value of the addition of 18-crown-6 and acetonitrile demonstrated conclusively that both were required in order to achieve unambiguous baseline separation of ammonium, potassium and monomethylammonium ions. The major advantages of the use of this electrolyte are a total run time of less than 7 min and symmetrical peak shapes. Validation on a series of preblast and postblast explosives materials determined that this procedure is reliable and robust.