TLC identification adn GLC determination of meperidine and its metabolites in biological fluids

Procedures were developed for TLC identification and GLC determination of meperidine and its metabolites, i.e., p-hydroxymeperidine, normeperidine, and meperidinic and normeperidinic acids. Meperidine, p-hydroxymeperidine, and normeperidine were extracted with ether from biological fluids at pH 10, whereas meperidinic and normeperidinic acids and conjugated metabolites remained in the aqueous phase. The residue, upon evaporation of the extract to dryness, was derivatized with trifluoroacetic anhydride and gas chromatographed. Total (free and conjugated) meperidinic and normeperidinic acids in the aqueous phase were converted and determined as meperidine and normeperidine, respectively. A preliminary result of urinary disposition of meperidine and its metabolites in the rat is presented. The identity of these metabolites was confirmed with GLC-mass spectrometry.