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Shulgin AT, Helisten C. 
“Differentiation of PCP, TCP, and a contaminating precursor PCC, by thin layer chromatography”. 
Microgram. 1975;8:171-172.
Analyses of drugs alleged to be mescaline or synthetic THC have often shown them to be phencyclidine (Sernyl, PCP). This base has also been encountered as a component in drug mixtures involving marijuana and LSD. Recently a pharmacologically related analog thienylcyclohexylpiperidine (TCP) has appeared in the place of, or in admixture with, PCP. In the illicit synthesis of both PCP and TCP, the intermediate 1-piperidinocyclohexanecarbonitrile (PCC) is usually employed. This material has extraction properties that are extremely similar to those of both PCP and TCP, resulting in the prepar-ation of a contaminated product. As a toxicological problem, this contaminant may contribute to the toxic aspects of these two drugs and its presence or absence might be of value in the treatment of cases of overdosage. From the forensic point of view, the ability to detect this precursor should be potentially valuable in two ways: 1. It will help establish the synthetic procedure employed in the manufacture of the drug in question, and 2. As PCC is not found as a contaminant in preparations intended for clinical application, its presence will establish the unlicenced nature of this manufacture. Attempts to effect this analysis by conventional GLC procedures are thwarted by the thermal instability of PCC. Under ordinary chromatographic conditions, HCN is split out of the molecule resulting in the formation of the enamine cyclohexenylpiperi-dine. This process occurs during actual passage through the GLC column resulting in an inconsistent spectrum that depends upon column conditions, quantities injected, and the nature of the contamination of the injected sample. A further complica-tion is the inherent instability of this enamine in that, if hydrolytic conditions are encountered, it further degrades to its two components piperidine and cyclohexanone. Both of these latter chemicals are invariably lost under the solvent peak on GLC analysis. Attempts to analyze these mixtures by conventional TLC procedures (activated plates, heated spot application) result in immediate and complete degradation of PCC to these same components.
Notes # : Thanks to ASRI and Isomer Design
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