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Raman spectroscopy has been used to identify the date rape drug GHB and its precursor GBL in simulated spiked drinks. Importantly, the technique can be used with a wide variety of beverages in different types of containers included coloured glass, plastic beakers, and polythene bags. The work will be of direct forensic use but also lead to a portable device for checking drinks. Gamma hydroxybutyric acid (GHB) is colloquially known as "liquid ecstasy", but that blithe-sounding name belies the drug's reputation as a chemical facilitator of sexual assaults, or date rape. The incidence of date rape where GHB has been involved is somewhat skewed by sensationalist reporting in the tabloid media, however. Recent evidence suggests that excessive consumption of alcohol is more commonly to blame than GHB abuse. Nevertheless, the ability of this drug to render a person insensible relatively quickly and the fact that it can be used to spike drinks invisibly makes it an important issue to address. GHB was developed in the 1960s as a central nervous system and was used in medicine to treat sleep disorders, depression, and anxiety disorders as well as in treating withdrawal symptoms in opiate and alcohol addiction. At low dose, the drug induces euphoria, increases sensuality and removes inhibitions. As such it has become an increasingly popular recreational drug used together with other drugs such as cocaine and amphetamines. The research team led by Howell Edwards and Tasnim Munshi, with Michael Hargreaves and Victoria Brewster of the Molecular Spectroscopy Research Group, Chemical & Forensic Sciences, at the University of Bradford, UK, explain that GHB and its corresponding lactone gamma-butyrolactone (GBL) reach an equilibrium in solution in which a higher concentration of lactone is favoured when the solution is alkaline and GHB is favoured at pH less than 4. Forensic analysis usually relies on high performance liquid chromatography (HPLC), gas chromatography coupled with mass spectrometry (GC-MS), nuclear magnetic resonance or infra-red spectroscopy. Moreover, it usually requires the extraction of the drug from a suspect sample before analysis is possible. Raman spectroscopy, on the other hand, is a quick and simple, non-destructive technique that provides qualitative and quantitative information. It might therefore be used to identify substances at the scene of crime or at customs inspection points at shipping ports and airports. The sample need not be removed from the transparent container in which it is found. As such, the team has studied how well standard bench-top Raman spectroscopy and portable systems might be used to identify GHB and GBL in mildly acidic drinks initially spiked with GHB. "Raman spectra were obtained using three different spectrometers: one bench-top spectrometer, a Renishaw InVia Reflex dispersive spectrometer and two portable spectrometers, a Renishaw RX210 ?Raman-in-a-suitcase? (RIAS) portable Raman analyser, and a Delta Nu Inspector Raman FSX," the team says. Initially, the researchers simulated the kind of generic samples that a forensic scientist or customs official might face. They then carried out more detailed tests on different solutions in different containers. The team explains that the average volume of an alcoholic drink, such as gin & tonic, vodka and lemonade, or white wine, is around 150 to 200 millilitres, the common dosage level of GHB is about 2.5 to 4.0 grams, making an average concentration of 1.5 to 3% weight to volume in a spiked drink. The researchers therefore hoped to demonstrate that Raman could reveal such concentrations of GHB and GBL. "We are able to detect GHB and GBL in a variety of containers including colourless and amber glass vials, plastic vials and polythene bags," explain the researchers, "We have also demonstrated the ability to detect both GBL and GHB in a range of liquid matrices simulating spiked beverages." The lower concentration limit was 1% w/v, which is significantly lower than the common dosage level the team says. "This work clearly demonstrates that portable Raman spectrometers can be used to interrogate samples in situ," the researchers conclude, "allowing a more thorough investigation of key samples by Raman and other analytical techniques in a forensic laboratory where applicable." Related links:
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