Phenmetrazine or ephedrine? Fooled by library search.

Chemical and/or thermal conversion of analytes in a sample and/or GC injector can mislead the identification of analytes in a toxicological screening. In addition, library search can even more complicate the identification. The risk for false positive identification of phenmetrazine in an ephedrine-containing sample analysed by GC-MS is described. Ephedrine reacted with formaldehyde contamination in solvents to a compound with a similar mass spectrum as phenmetrazine. High injection temperatures influenced the formation speed.