Drug use in populations, both legal and illegal, is important to know about for health and law and order reasons. Whilst it is relatively easy to keep tabs on the amount of legal drug use by asking pharmacies and other resellers, the purveyors of illegal drugs are unsurprisingly reticent with this sort of information. It is possible to study the users with questionaires, but they are not always accurate,
Drugs are not all destroyed by the body, and many are excreted, and so end up in the sewers, so one obvious place to look is there. The problem is that many illegal drugs are the same molecule as another legal counterpart, or can be created in the body from a legal molecule so it is hard to tell the difference.
Barbara Kasprzyk-Hordern and David Baker at the University of Huddersfield have used the fact that although both versions are often the same molecule parts of the molecules can be mirror images of one another, forming enantiomers. The ratio of these is often different in the legal and illegal versions.
They studied waste water from a variety of treatment works using liquid chromatography machines to seperate out different molecules, and their enantiomers and mass spectrometry to give a better idea what the molecule is.
They found various different drugs in the waste water including amphetamine, methamphetimine, MDMA or ecstasy, and ephidrine. By studying the percentage of the different enantiomers they could show how much of each was illegal useage.
The technique obviously needs a lot of calibration, as they do not yet know how the different molecules behave in sewage systems, but it could be an important tool in understanding just what is being used out there.