Direct immersion solid phase microextraction for the forensic detection of explosives in post-blast water samples

Abstract

The forensic identification of bulk explosives plays a significant role in bombing investigation. The type and composition of explosives can be used to link suspects to a bombing crime. In this study solid- phase microextraction (SPME) was employed for the recovery of seven selected nitro explosives from the aqueous samples using gas chromatography-electron capture detector (GC-ECD). SPME parameters including extraction time, desorption time, desorption temperature, and the concentration of sodium chloride (NaCl) for salting-out effect were optimized using Carboxen/polydimethylsiloxane (CAR/PDMS)-coated fiber. Addition of 10% (w/v) of NaCl in the aqueous compounds under study for the optimized SPME method was found to be within 2 to 10 ppb except for PETN (1.4 ppm). Solid-phase extraction (SPE) utilizing LiChrolut® EN sorbent was employed for an analyte preconcentration technique prior to SPME in post-blast water samples collected from sampling trays. Three water samples collected at two sampling points nearest to the explosion point were found to contain traces of PETN (0.020 – 0.039 ppm). SPE-SPME with direct immersion mode followed by GC-ECD analysis was found to be a viable method for the qualitative and quantitative analysis of explosive residues in post-blast water samples.