Determination of inorganic ions in explosive residues using capillary zone electrophoresis

Five anions (chlorate, perchlorate, nitrate, nitrite, and sulfate) and two cations (ammonium and potassium) in explosive residues were separated and determined using capillary zone electrophoresis (CZE) with indirect ultraviolet (UV) detection. The electrolyte buffer solution for the cation separation was 10 mmol/L pyridine (pH 4.5)-3 mmol/L 18-crown-6-ether. Ammonium and potassium ions were baseline separated in less than 2.6 min with the detection limits of 0.10 mg/L and 0.25 mg/L (S/N = 3), respectively. The electrolyte buffer solution for the anion separation consisted of 40 mmol/L boric acid-1.8 mmol/L potassium dichromate-2 mmol/L sodium tetraborate (pH 8.6). Tetramethyl ammonium hydroxide (TMAOH) was used as an electro-osmotic flow modifier. All five anions were well separated in less than 4.6 min with the detection limits of 0.10 to 1.85 mg/L (S/N = 3). This method was successfully used in the investigations of real samples for the confirmation of explosive types.