Besides the enantiomeric purity of the methamphetamine, many other substances may be introduced into the drug mixture. The crude methods employed by the factories would most likely produce many minor products, such as other phenethyl amines and amphetamines. Also, the synthesis would never consume all the starting materials, so some ephedrine and psuedo-ephedrine may remain. In addition the the by-products, the manufacturers introduce several catalysts for methamphetamine's biochemical interaction with the central nervous system. The article mentioned two, cyanide and phosphorous pentachloride. The favorite method of forensic scientists for the analysis of street mixtures of drugs is the combination of Gas Chromatography and Mass Spectrometry. This allows the identification of the most compounds with a single run. Other methods such as IR and NMR may be used; however, GC/MS is the preferred strategy.