Quality assurance testing of an explosives trace analysis laboratory — Further improvements to include peroxide explosives

The Forensic Explosives Laboratory (FEL) operates within the Defence Science and Technology Laboratory (DSTL) which is part of the UK Government Ministry of Defence (MOD). The FEL provides support and advice to the Home Office and UK police forces on matters relating to the criminal misuse of explosives. During 1989 the FEL established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels that could, if other precautions failed, result in the contamination of samples and controls. Designated areas within the laboratory are swabbed using cotton wool swabs moistened with ethanol:water mixture, in equal amounts. The swabs are then extracted, cleaned up and analysed using Gas Chromatography with Thermal Energy Analyser detectors or Liquid Chromatography with triple quadrupole Mass Spectrometry. This paper follows on from two previous published papers which described the regime and summarised results from approximately 14 years of tests. This paper presents results from the subsequent 7 years setting them within the context of previous results. It also discusses further improvements made to the systems and procedures and the inclusion of quality assurance sampling for the peroxide explosives TATP and HMTD. Monitoring samples taken from surfaces within the trace laboratories and trace vehicle examination bay have, with few exceptions, revealed only low levels of contamination, predominantly of RDX. Analysis of the control swabs, processed alongside the monitoring swabs, has demonstrated that in this environment the risk of forensic sample contamination, assuming all the relevant anti-contamination procedures have been followed, is so small that it is considered to be negligible. The monitoring regime has also been valuable in assessing the process of continuous improvement, allowing sources of contamination transfer into the trace areas to be identified and eliminated.