A gas liquid chromatography (GLC) for the determination of alfentanil in plasma of surgical patients is described. The assay involved a preliminary ethereal extraction of alfentanil and fentanyl (as internal standard) in a 0.5 ml plasma sample under alkaline conditions. The dried extract was dissolved in n-heptane (10 µl) and 1µl-aliquot was analysed by a Varian GLC system consisting of a SE-30 capillary column (16 m x 0.25 mm) linked to a nitrogen selective detector. The recovery of alfentanil from plasma samples at 250 ng ml-1 ranged from 84 to 92% (n = 10, mean 88%) with a coefficient of variation of 2.7%. Calibration graphs, over the concentration range of 5 to 500 ng ml-1, relating the peak height ratios of alfentanil to the internal standard were linear (n = 6; coefficients of variation ranging from 2.4 to 5.7%). The assay was used to measure the plasma concentrations of alfentanil in 4 surgical patients during and after its intravenous infusion and when spontaneous ventilation was re-established at the end of surgery.
- human plasma,
- gas liquid chromatography,
- capillary column
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