A simple and quick fingerprint test to identify cocaine users has been developed.
It can distinguish in just a couple of minutes between those who have taken it or simply been exposed by mistake – even after they have washed their hands.
The groundbreaking technique could lead to the screening of staff – especially in workplaces where public safety is an issue.
It could also aid drug rehabilitation, the management of offenders and coroners when a body first arrives at a mortuary. It is based on chemicals excreted in sweat.
Study co-author Dr Min Jang, of the department of chemistry at the University of Surrey, said: "A fingerprint is a great way to test for drugs as it is so quick and efficient to collect.
"Using our methodology, it is possible to analyse a fingerprint sample for drugs in less than 2 minutes."
In particular benzoylecgonine, produced in the body when cocaine is ingested, tells those who have consumed it from those who have handled it.
The molecule was not present in samples from non-users of the Class A drug, even after touching street cocaine and then washing their hands.
Lab member Dr Catia Costa said it could also be used for heroin, cannabis or amphetamines.
She said: "We are excited about the possibilities for fingerprint drug testing. In addition to illicit drugs, we have found we can detect pharmaceutical drugs in fingerprints.
"We are keen to see if we can use this to help patients to check their medication is being delivered at the right dose."
In a series of experiments described in Scientific Reports the test accurately and painlessly picked out cocaine users using a single sample.
Fingerprints were collected from people seeking treatment at drug rehabilitation clinics who had admitted taking cocaine during the previous 24 hours.
The participants were then asked to wash their hands thoroughly with soap and water before giving another set of fingerprints.
This same process was used to collect samples from a pool of drug non-users who had touched street cocaine.
The researchers then used a scanning technique called rapid, high resolution mass spectrometry to cross-reference the information from both groups.
For drug testing, it is vital to distinguish those who have handled cocaine from those who have ingested.
The legal ramifications are huge where issues such as drug driving are involved, said the researchers.
Dr Melanie Bailey, also at the University of Surrey, said: "We think this research is really significant as our laboratory test using high resolution mass spectrometry can tell the difference between a person who has touched a drug and someone who has actually consumed it – just by taking their fingerprints."
A similar drug screening system using different scanning techniques to detect specific drugs in sweat is already available from Cambridge based Intelligent Fingerprinting .
Founder and chief scientific officer Professor David Russell said: "This University of Surrey laboratory study into cocaine testing using experimental high resolution mass spectrometry techniques validates the approach Intelligent Fingerprinting took when originally commercialising our portable fingerprint-based drug screening system for use at the point-of-care.
"Because our commercially-available test detects both cocaine traces and benzoylecgonine – the major metabolite of cocaine – our customers have been successfully using fingerprint-based drug tests since the summer of 2017 to determine whether cocaine has actually been taken."
Around a third of UK adults aged 16 to 59 have taken illegal drugs at some point during their lifetime, almost one in twenty in the last month. Cocaine is the second most popular, behind cannabis.
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