Gas-liquid chromatography of undervatized drugs after chromatographic extraction from blood.

We have developed an integrated method that overcomes the two main procedural difficulties of gas-liquid chromatography, namely, solvent-solvent extraction and chemical derivatization. Drugs are extracted from serum by column chromatography on granular diatomaceous earth (kieselguhr). Subsequent gas-liquid chromatography of underivatized samples can be performed on either of two liquid phases. A mixed liquid phase, used for quantitative gas-chromatographic assay on patients with a known therapeutic regimen, has enabled quantitation of 12 drugs in serum. Alternatively, a single liquid phase, used with the mixed liquid phase, permits the gas-chromatographic identification of unknown drugs on the basis of the characteristic pattern of the two relative retention times; by this approach more than 40 drugs have been identified in cases of suspected intoxication, both in serum and in gastric aspirate. Besides providing ease of performance and wide applicability, the proposed procedure offers a degree of precision and accuracy that compares favorably with established methods.