Assays - Codeine

Determination of Codeine in human plasma by reversed-phase high-performance liquid chromatography

Author: V. Nitsche, H.J. Mascher
Publisher: J. Pharm. Sci. 73 (1984), 1556-1558

Plasma from volunteers dosed with codeine was cleaned-up on a column of C18, from which codeine was eluted with methanol - 0.1 M HCl (1:1). Following addition of diazepam as internal standard, codeine was separated by reversed-phase HPLC on a column (25 cm x 4 mm) of Polygosil C18 (7.5 µm) operated at 45°C with methanol - 0.1 M ammonium carbonate (7:3) as mobile phase (2 ml/min) and detection at 220 nm. Calibration graphs were linear in the range 10 to 300 µg/l of codeine. Analysis took 3.5 min per run. The limit of detection was ~ 3 µg/l for 0.8 ml of plasma and a 40 µl loop. For a 150 µl loop and larger vol. of plasma, the detection limit can be reduced to < 1 µg/l. No interference was observed from drugs frequently co-administered with codeine. Recovery from doped samples was 98.4 ± 6.6 % (n = 16). Results of bioavailability studies agree well with those obtained by other methods, and the method is suitable for pharmacokinetic and clinical detection of codeine in plasma.