Mass Spec Tracks Down Designer Drugs

Drug tests typically spot banned substances one at a time using a spectroscopic signature of the substance. Clever chemists in turn design new drugs with minor chemical modifications to evade such detection. A mass spectrometry technique can now screen for many variations all at once (Anal. Chem., DOI: 10.1021/ac300509h). “Herbal incense” products typically contain psychoactive synthetic cannabinoids, says Megan Grabenauer of RTI International. To develop a general detection method, Grabenauer borrowed a technique from metabolomics called mass defect filtering, which can distinguish among related compounds. The mass defect, or fractional mass, is less than 1 dalton and is the part of a substance’s molecular mass that lies to the right of the decimal point. This fraction changes little, even when functional groups are added or subtracted and the number on the left of the decimal changes significantly. The fractional mass of JWH-018, a banned synthetic cannabinoid, is 0.18 Da. The researchers checked the mass spectra of 32 locally purchased herbal mixtures with names such as “Mr. Nice Guy” and “Hot Hawaiian” for compounds with fractional masses between 0.13 and 0.23 Da. They then sampled those compounds and compared the masses of the fragments with those of JWH-018 and other synthetic cannabinoid standards. From these data, the researchers identified at least one synthetic cannabinoid in each herbal mixture. In addition to JWH-018, they found one other illegal cannabinoid and seven that are not regulated.