rofilling of inorganic ions in selected post-blast pyrotechnic residues

Abstract

Pyrotechnic homemade explosives have emerged as a new threat to society. Analysis of explosive residues is useful in identification of explosives and establishing link to the perpetrators. The objectives of this study were to detect the selected inorganic ions in firework samples followed by the determination of chemical profiles. Six different types of firework samples were analyzed in this study. Inorganic ions of pre-blast and post-blast samples were analyzed using ion chromatography with conductivity detection. All targeted anions (F-, Cl-, NO2-, NO3-, ClO3-, SO42-, PO43- and SCN-) were successfully separated within 42 minutes using Metrosep A SUPP 5 column and NaHCO3-Na2CO3 as the eluent. Calibration graph of targeted anions with good linearity (r2>0.9796) were obtained with detection limits within range from 16 to120 µg/L. Besides that, all targeted cations (Li+, Na+, NH4+, K+, Ca2+, Mg2+) were well separated within 24 minutes using Metrosep C 4 employing nitric acid-dipicolinic acid as the eluent. Good linearity (r2>0.9948) of calibration graph was obtained and detection limits was 31-171 µg/L. Anions (Cl-, NO2-, NO3-, ClO3- and SO42-) and cations (Na+, NH4+, K+, Ca2+, Mg2+) were detected in pre-blast firework samples. Concentration of NO3-, ClO3- and K+ were the highest among detected ions in pre-blast samples. Magnesium ion which is a common element in fireworks was detected in all samples. In post-blast residues, targeted ions presence in pre-blast samples can still be detected but in lower concentration. There was significant reduction in NO3- and ClO3- concentration in post-blast residues. Concentrations of SO42- are relatively higher compared to other anions detected in post-blast residues. Identification of fireworks cannot be based solely on chemical profile of post-blast residues as it is not fully accurate. However, presence of Ca2+ and Mg2+ in post-blast residues strongly suggest the used of pyrotechnic fireworks.