Last Month's Most Accessed Feature: Lending a hand: Cocaine metabolites in fingerprints confirm drug taking
- Published: Jul 6, 2015
- Categories: Base Peak
The use of fingerprints, also know these days as fingermarks, in the forensic world is set for expansion due to recent developments. Not only can they be used to identify suspects from the ridge pattern, but they can also reveal more information about their owners, such as gender, drug taking or drug handling, and the presence of condom lubricants.
Much of the recent work has been carried out by Simona Francese at Sheffield Hallam University who has illustrated the advantages of surface mass spectrometry techniques operating in the open air for getting fast results from fingerprints. Now, she has collaborated with Melanie Bailey from the University of Surrey and researchers from the National Physical Laboratory, UK, the King’s College London Institute of Pharmaceutical Sciences and the Netherlands Forensic Institute at The Hague to devise a rapid test that could show that a suspect has been taking cocaine.
Earlier research showed that cocaine can be detected in fingerprints, but the source of the drug could not be ascertained. This new work looks not only for cocaine itself but also for its two major metabolites. The presence of all three would be a strong indication that cocaine had been ingested, rather than simply handled.
Open air mass spectrometry testing
Latent fingerprints were gathered on glass slides from five individuals participating in a drug treatment program and saliva was also collected for comparative tests. The fingerprints were analysed by two contrasting surface mass spectrometric techniques.
In the first, the analysts used matrix-assisted laser desorption/ionisation-ion mobility-mass spectrometry to look for the cocaine metabolite benzoylecgonine (BZE). This technique separates ions on the basis of their drift time down a tube followed by their m/z values, so provides an extra dimension for separation. BZE was clearly detected, with confirmation from its tandem mass spectrum on the high-resolution instrument.
For the second technique, the analysts were asked to search for a second cocaine metabolite, methylecgonine (EME), as well as BZE. They were observed by desorption electrospray ionisation (DESI) mass spectrometry and both were found in fingerprints. In a repeatability test, three fingerprints from two additional volunteers were analysed in three positions each and BZE and EME were found in all but one point.
Metabolites point to cocaine consumption
The fact that BZE and EME are both found in a fingerprint does not automatically mean that the subject has taken cocaine because there might be other possibilities. For instance, it has not yet been determined whether cocaine can be converted into these two metabolites on the skin surface or whether they might be transferred from someone else or another surface.
Nevertheless, their discovery in fingerprints by techniques that can give results within two minutes provides the basis for a novel drug testing method that is both rapid and secure. Since the fingerprint can be linked to the suspect, there is no chance of cheating the system.
"The beauty of this method is that, not only is it non-invasive and more hygienic than testing blood or saliva, it can’t be faked," said Bailey. "By the very nature of the test, the identity of the subject is captured within the fingerprint ridge detail itself." And the test would be simple, with little or no sample preparation.
One of the challenges remaining is to expand the detection of cocaine metabolites to their measurement. This is not straightforward because fingerprints are not uniform and the distribution of substances within them can vary, but the researchers are "optimistic" that methods can be developed.
With the drive towards smaller, portable mass spectrometers, it seems only a matter of time before methods like this can be rolled out for onsite analysis in police cells after arrest, saving much time in the investigation process. "We are only bound by the size of the current technology. Companies are already working on miniaturised mass spectrometers, and in the future portable fingerprint drugs tests could be deployed. This will help to protect the public and indeed provide a much safer test for drug users," said Bailey.
Analyst 2015 (Article in Press): "Rapid detection of cocaine, benzoylecgonine and methylecgonine in fingerprints using surface mass spectrometry"
Article by Steve Down
The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.
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