Comparative determination of total isomeric truxillines in illicit, refined, South American cocaine hydrochloride using capillary gas chromatography electron capture detection

The isomeric truxillines and their hydrolysis products are present as manufacturing impurities in most illicit, refined cocaine samples. Methodology is described for the comparative gas chromatographic determination of total isomeric truxilline manufacturing impurities/by-products, i.e., intact truxillines and their hydrolysis products, in illicit, refined cocaine samples seized in South America. These isomers, namely, alpha-, beta-, delta-, epsilon-, gamma-, omega-, zeta-, peri-+neo- and epi-truxilline, were all quantified relative to mu-truxillic acid, a structurally-related internal standard. In this method, the cocaine samples were first subjected to treatment with boron trifluoride-methanol, followed by lithium aluminum hydride reduction and then acylation with heptafluorobutyric anhydride. The resultant di-heptafluorobutyryl derivatives of the truxillyl and truxinyl diols exhibited excellent chromatography and low-picogram on-column detection when using a moderately polar fused-silica capillary column interfaced with an electron-capture detector. This methodology demonstrated good reproducibility, as determined by the repetitive analysis of a selected illicit cocaine exhibit. The analysis of 117 unadulterated, illicit, refined cocaine samples revealed that total truxilline levels ranged from 0.2-12.3% (w/w relative to cocaine), with the two most abundant truxillines being the alpha- and beta- isomers. Truxilline data for the total individual truxilline isomers in cocaine hydrochloride exhibits from five South American countries are presented.