Work

Elemental and isotopic profiling of potassium perchlorate salts for forensic explosives investigations

Year: 2025

Type: article

Abstract: This study explores the feasibility of using isotopic and elemental signatures for the source attribution of potassium perchlorate (KClO 4 ) salts, which can play a significant role in forensic explosives investigations. A total of 41 different reference KClO 4 batches were analysed using isotope ratio mass spectrometry and inductively coupled plasma – mass spectrometry. Rubidium was the only elemental impurity detected consistently across all reference batches. Combined with the oxygen isotopic composition, these features provide a discriminating power of 94 %. A score-based likelihood ratio (LR) system was developed also including concentrations of sodium, magnesium, chromium, and iron, which were detected in 69–98 % of the reference samples and showed significant variation between sources. The LR system employs Manhattan distance and kernel density estimation to model (dis)similarity across source comparisons. Five-fold cross validation results suggest the LR system effectively distinguishes between same-source and different-source pairs (C llr = 0.184) and can be used to report LR values of up to 74 (moderate support). Infrequently detected trace elements and chlorate concentrations allow for a more comprehensive interpretation of chemical profile analyses and should also be considered to uphold forensic integrity. A series of tests have established a reliable method for the reduction of KClO₄ to KCl for subsequent chlorine isotope ratio – mass spectrometry ( δ 37 Cl -IRMS) measurements, which could provide additional discriminating power. Further research is required to develop a scalable process that yields sufficient material for δ 37 Cl-IRMS and to ensure that the sample preparation process yields reproducible δ 37 Cl values. • Rubidium, sodium, magnesium, chromium, and iron are discriminating impurities. • Rubidium is the only element impurity consistently found in potassium perchlorate. • IRMS and ICP-MS analyses can provide moderate support of source-level hypotheses. • Chlorine isotopic composition and chlorate content can offer additional support.

Source: Forensic Chemistry

DOI: 10.1016/j.forc.2025.100666