Liquid chromatography of codeine in plasma with fluorescence detection.

This analytical method for easier determination of codeine in human plasma is based on "high-performance" liquid chromatography for separation and the natural fluorescence of codeine for detection. Codeine is extracted from alkalinized plasma with a mixture of hexane and dichloromethane, and the extract is further purified and chromatographed. The method can be used for routine assay of codeine at the concentrations of 10 micrograms/L or greater in human plasma. As little as 4 micrograms/L can be detected. Coefficients of variation for the assay of codeine in the concentration range of 10 to 100 micrograms/L were 2.2-7.4% (n = 6). We used this method to establish a concentration/time profile for plasma from a human volunteer after a 60-mg oral dose of codeine sulfate.