Analytical aspects of barbiturate abuse: identification of drugs by the effective combination of gas-liquid, high-performance liquid and thin-layer chromatographic techniques.

Chromatographic retention data for a group of barbiturates have been measured on seven chromatographic systems (two gas--liquid chromatographic (GLC), three high-performance liquid chromatographic (HPLC) and two thin-layer chromatographic systems) and the value of these for barbiturate identification has been discussed. The overall correlations observed between pairs of systems are generally low; however, specific groups of barbiturates show very high correlations and this determines the approach to the selection of two or more systems to increase chromatographic discrimination of the barbiturate group. Column chromatographic techniques with lipophilic phases (GLC using SE-30, HPLC using ODS-silica) are most suitable for barbiturate identification. Changes of eluent pH in reversed-phase HPLC proved very effective for the separation of barbiturates with closely related structures.