Last Month's Most Accessed Feature: New psychoactive substances: Active ingredients by selected reagent ionisation mass spectrometry
- Published: Apr 6, 2015
- Categories: Base Peak
Classifying blends of new psychoactive substances
In a calculated move to overcome restrictions on illegal psychoactive drugs such as cocaine and cannabis, many online vendors are turning to concoctions that contain legal substances that are supposed to mimic their effects. Some are comprised of allegedly pure substances while others are blends of several components and their analysis can be difficult.
A European team of scientists from Austria and the UK has applied an unusual form of mass spectrometry to see how that might fare against these blends. Philipp Sulzer and colleagues from IONICON Analytik GmbH, Innsbruck, Leopold-Franzens Universität Innsbruck, Lancaster University and the University of Birmingham described their approach in Journal of Mass Spectrometry. It involved selective reagent ionisation linked to time-of-flight mass spectrometry which has several advantages over conventional drug analysis methods.
GC/MS and LC/MS are commonly used for drug testing but both methods are not especially fast, even the quickest setups taking several minutes. In contrast, the new SRI MS method can complete an analysis within 30 seconds while maintaining the strict requirements of selectivity and sensitivity. It relies on prior knowledge of the relative abundances of the product ions that are produced by ion/molecule reactions of the neutral drug species with the "selective reagents" but that is similar to conventional mass spectrometry in which knowledge of the fragment ions or MS/MS spectra is required.
SRI MS has been applied previously to the detection of single chemicals in drug preparations but its effectiveness against blends of drugs like those available over the Internet has not yet been tested. Many sources do not declare the compositions of the products that they offer for sale.
Selective reagent ionisation of synthacaine
For the measurements, a little of the suspect sample was placed in a glass vial which was heated to drive the components into the headspace from where they were mixed with pure air and directed into the drift tube. Here, they encountered a flow of H3O+ ions produced from water vapour by a hollow cathode discharge ion source.
Any compounds from the sample with a proton affinity greater than that of H3O+ would undergo a proton transfer reaction to produce protonated molecules from the sample which were detected in the time-of-flight mass spectrometer.
The researchers acquired a sample of synthacaine from an online vendor. It was a so-called legal cocaine but there was no mention of any ingredients. A search of online forums had suggested that the most common ingredients used to prepare synthacaine were the local anaesthetics benzocaine and lidocaine and the stimulants methiopropanamine, 4-methylethcathinone, caffeine, ethylphenidate and dimethocaine.
When they ran their sample, two peaks were observed that corresponded to the protonated molecules of benzocaine and methiopropanamine and the remaining peaks could also be assigned to fragments of both compounds. No peaks from any other potential ingredients were detected. So, it was clear that this sample of synthacaine contained these two active components.
Confirmation from ion branching ratios
Although this evidence was strong, the SRI MS technique can provide powerful evidence to back up the assignments. When the collisional energy of the H3O+ and analyte species was varied by adjusting the voltage applied across the drift tube, the fragmentation patterns of the analytes were affected. This occurred in a predictable manner so that the patterns of unknown compounds could be compared to those pre-recorded for standard compounds to confirm the identities.
Not only was this accomplished with H3O+ as the reagent ion, but also with NO+, which was produced by substituting charcoal-filtered air for water vapour in the source. NO+ reacts by dissociative charge transfer to produce a different series of ions for compound identification. So, the presence of benzocaine and methiopropanamine was confirmed from the two sets of branching ratios.
SRI MS identifies the components but does not measure them. However, it does so with a high degree of confidence and in a very short time, taking just 30 s in all. The first reaction with H3O+ takes 5 s, switching the drift tube voltage and measuring the change in branching ratios takes another 5 s, switching the reagent ion to NO+ and recording the ions takes 10 s, then returning the voltage to its initial value and measuring the new branching ratios for NO+ takes 5 s.
The research team suggested that SRI MS would be useful for law enforcement agencies and medical staff due to its speed of operation, where it could give rapid results in cases of suspected drug overdoses or allergic reactions. Its application would be accelerated by the development of an automated procedure and a reference library of ion branching ratios that would simply display to the operator the names of any compound present in a psychoactive drug blend.
Journal of Mass Spectrometry 2015, 50, 427-431: "Selective reagent ionisation-time of flight-mass spectrometry: a rapid technology for the novel analysis of blends of new psychoactive substances"
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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