Improved high-performance liquid chromatographic method for the determination of ethylmorphine and its metabolites in microsomal incubations and cell culture media. |
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Authors: | G A van't Klooster F M Woutersen-van Nijnanten H J Kolker J Noordhoek A S van Miert |
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Institution: | Department of Veterinary Basic Sciences, University of Utrecht, Netherlands. |
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Abstract: | Ethylmorphine N-demethylation is used as a marker pathway in studies of rat cytochrome P450 3A and 2C11 biotransformations. At present, microsomal activities are generally measured by a colorimetric determination of the formed formaldehyde. In the present study, a high-performance liquid chromatographic method of separating and quantifying both the N-demethylated (norethylmorphine) and the O-de-ethylated (morphine) metabolites is described. Either samples are extracted with ethyl acetate or proteins are precipitated with zinc sulphate-barium hydroxide. Separation is achieved on a CN reversed-phase column, using a mobile phase of phosphate buffer (pH 4.5)-acetonitrile (90:10, v/v). At a flow-rate of 1.5 ml/min, the analysis time is 30 min. The limit of detection (ultraviolet, 210 nm) for ethylmorphine and its metabolites is 0.5 micrograms/ml. |
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