Professor/Director, Forensic Science Unit, University of Strathclyde, Glasgow,
Associate Professor, Central Police University, Kwei-Shan, Taoyuan, Taiwan
A reversed-phase high-performance liquid chromatographic method using 9-fluorenylmethylchloroformate (FMOC) as fluorogenic labeling reagent for the detection of ethyl centralite (EC) and 2,4-dinitrotoluene (2,4-DNT) in gunshot residues is reported. Residues were sampled with cotton wool swabs which were then extracted and the extracts cleaned by TLC. The sample spots on the TLC plate were scraped off and extracted to recover the analytes. The extract corresponding to EC was hydrolyzed while 2,4-DNT was reduced. The hydrolysis and reduction products (N-ethylaniline and 2,4-diaminotoluene, respectively) were derivatized with FMOC in alkaline buffer solution at 52°C for 20 min. The derivatives were analyzed by a reversed-phase HPLC with fluorescence detection. The detection limits for EC and 2,4-DNT were 200 pg and 1 ng per standard sample, respectively. Three out of eleven kinds of gunpowders analyzed were found to contain EC, while another three were found to contain 2,4-DNT. According to the results of gunpowder analysis, two different kinds of ammunition, which were presumed to contain EC in one and 2,4-DNT in the other, were chosen for test firings. Ethyl centralite was detected in cotton swabs sampled from spent cartridge cases of both of these two kinds of ammunition, but 2,4-DNT was not detected in any of these spent cases. Nine out of twelve samples swabbed from shooting hands at various times after firing two rounds of either kind of ammunition were found to contain EC, while none of these swabs were found to contain 2,4-DNT. The quantities of EC recovered from these hand swabs were shown to be in the range of 0.6 to 4.0 ng.
Paper ID: JFS15416J