Detecting drugs with the compact Powder Puck

Determining which drug an unknown white powder is – or ruling out that it is a drug at all – typically requires an extensive process in a chemical laboratory. Researchers from the Dutch Police and the University of Amsterdam published a method for measuring powders quickly and reliably on-site. To this end, they developed the Powder Puck (see photo), which contains portable near-infrared (NIR) analytical equipment. It combines wavelengths between 1300 and 2600 nm with a chemometric model they developed specifically for forensic purposes. Unlike most models, this model contains a small number of reference spectra, enabling results to be obtained rapidly.

A key advantage of this method is that measurements can be taken non-invasively, meaning whilst the substance remains in a plastic bag. This is not only considerably faster and more efficient, but also safer for the user, who does not need to be a forensic expert. Furthermore, it reduces the likelihood of so-called forensic risks, whereby the substance under investigation might, for example, accidentally become mixed with other substances. The results obtained for cocaine show >97% true positives; other drugs yielded comparable results.

The Powder Puck is, however, still less well-suited for the predominantly dark, coarse granules of amphetamine. Results were frequently unusable or incorrect. That said, false positives were reduced by grinding the substance further and placing it directly on the sensor without a bag. Nevertheless, this is also an indication that the data library is not yet sufficiently comprehensive. This may be related to the absence of a cutting agent or specific salt form in the database. Optimisation of the library is also still required for impure forms of drugs. This will therefore always remain a task for forensic experts: ensuring the database is complete and up to date.