IC Determination of Inorganic Ions in Explosive Residues

The contents of 5 anions and 5 cations in explosive residues were determined by ion chromatography (IC). DIONEX IonPac AS11-HC Anion-exchange column with 20 mmol KOH solution as eluant was used for separation of the 5 anions, i.e., Cl-, NO3-, NO2-, SO42- and ClO3-, and DIONEX IonPac CS12A cation-exchange column with 20 mmol·L-1 methyl sulfonic acid as eluant was used for separation of the 5 cations, i.e., Na+, K+, NH4+, Ca2+ and Mg2+. Inhibitory conductivity detections were adopted in the determinations. Linearity was found in the same range of 0.1-100 mg·L-1 for all the 10 inorganic ions, with values of detection limit (3S/N) of 2.36 μg·L-1 for Cl-, 3.87 μg·L-1 for NO3-, 5.49 μg·L-1 for NO2-, 6.11 μg·L-1 for SO42- and 6.02 μg·L-1 for ClO3-, 3.05 μg·L-1 for Na+, 6.23 μg·L-1 for K+, 5.42 μg·L-1 for NH4+, 4.33 μg·L-1 for Ca2+ and 5.66 μg·L-1 for Mg2+. The proposed method was applied to the determination of 10 inorganic ions in explosive residues, giving values of recovery in the ranges of 91.2%-106.2% and 90.3%-102.3%, and RSD (n=6) in the ranges of 2.1%-3.8% and 1.1%-4.2% for the anions and cations respectively.