A simplified procedure for the isolation, characterization, and identification of weak acid and neutral drugs from whole blood.

The presented method utilizes commercially available Chem Elut columns for the extraction of weak acid and neutral drugs. The residue from this extraction is purified by partitioning between hexane and acetonitrile. The drugs are analyzed using a gas chromatograph equipped with a 0.53-mm i.d. dimethyl silicone capillary column, a packed column inlet adapter, and a flame ionization detector. The drugs are characterized by their retention index. The procedure is rapid, and clean chromatograms are the rule with essentially no lipid interference for flame ionization or mass spectrometer detection systems. The retention index has proven to be a very reliable parameter for describing chromatographic behavior. For probarbital, the internal standard, the calculated retention index averaged 1529.70 with a standard deviation of 1.27 index units (n = 115).