Quantitative determination of morphine in biological samples by gas-liquid chromatography and electron-capture detection

Abstract
A highly sensitive method for the determination of morphine in plasma and brain samples down to 500 pg ml−1 in plasma and 100 pg in 30 mg of brain tissue is described. This sensitivity is in the range of that described for radioactive and radioimmunological techniques. The samples (50–500 μl) are extracted with toluene–butanol (9:1) at pH 8.9 and then re-extracted into 0.1N sulphuric acid and back extracted to a toluene–butanol phase at pH 8.9. The pentafluoro-propionic anhydride derivatives of morphine and the internal standard nalorphine were quantitatively determined by gas–liquid chromatography with a 3H electron capture detector.