Analyzing elements’ isotope ratios can authenticate wines and cheeses, as well as expose clandestine labs where illicit drugs such as cocaine are made. Now, chemists report that this strategy also has the potential to detect the provenance of complex designer-drug mixtures known as bath salts, which provide users with a high but remain legal in many U.S. states. In May, Oliver B. Sutcliffe, Niamh Nic Daeid, and colleagues at the University of Strathclyde, in Glasgow, Scotland, published the first reliable liquid chromatography test for mephedrone, a common ingredient in bath salt powders (J. Pharm. Biomed. Anal., DOI: 10.1016/j.jpba.2011.05.022). They have now used isotope-ratio mass spectrometry to trace several structurally related substances in simulated bath salt samples, including mephedrone and methylenedioxypyrovalerone, back to their starting materials. The proof of the pudding, Sutcliffe said, would be to do the same thing with street samples, something the team plans to work on soon. He added that the team can identify the components of street samples with NMR, but he noted that NMR instruments are far rarer in forensic labs than are mass spectrometers and that the technique cannot link drugs to manufacturers.