High-performance liquid chromatographic assay for morphine with electrochemical detection using an unmodified silica column with a non-aqueous ionic eluent.

A quick, sensitive and accurate high-performance liquid chromatographic method for morphine measurement in plasma has been developed using an unmodified silica column with a non-aqueous ionic eluent. Small plasma samples (0.4 ml) were extracted with a liquid-liquid extraction column and dihydromorphine was used as internal standard. The limit of quantitation was 2 ng/ml. The electrochemical detector was capable of detecting 150 pg of morphine. A calibration line with a correlation of 0.9994 +/- 0.00026 was produced over the range 2-80 ng/ml.