Detection of N,N′-diphenyl-N,N′-diethylurea (ethyl centralite) in gunshot residues using high-performance liquid chromatography with fluorescence detection

Abstract

An HPLC with fluorescence detection method has been developed to detect N,N′-diphenyl-N,N′-diethylurea (ethyl centralite, EC) in gunshot residues. Residues were recovered with cotton wool swabs. Ethyl centralite was extracted from swabs, cleaned, and hydrolysed to yield N-ethylaniline (NEA). Any N-ethylaniline was dansylated in alkaline buffer solution at 52 °C for 30 min. The derivative was analysed by reversed-phase HPLC with fluorescence detection. The detection limit is 60 pg of NEA per injection. Accounting for the procedures of clean-up, hydrolysis, and dilution, this equates to 670 pg of EC recovered from a hand swab. Three out of eleven types of gunpowders analysed were found to contain EC. Ethyl centralite was detected in cotton swabs sampled from a spent cartridge case and the shooting hand of a subject immediately after firing two rounds of revolver ammunition. The quantities of EC recovered from these swabs were shown to be 193.4 and 1.89 ng, respectively.