A SEMI-AUTOMATED FLUORIMETRIC PROCEDURE FOR DETERMINATION OF PLASMA CORTICOSTEROIDS

A semi-automated procedure for the determination of plasma cortico-steroids is described, based upon the acid-induced fluorescence of cortisol. After manual extraction of plasma with dichloromethane, all steps are automated. The solvent is mixed with ethanolic sulphuric acid which extracts the cortisol. After a suitable delay the acid is separated and led to a continuous flow cell in a fluorimeter connected to a recorder. The method has been evaluated for reliability; in particular specificity has been checked by analysing human plasma samples by the technique described and also by a chromatographic method for cortisol and corticosterone for comparison. This showed that the automated fluorimetric method gave a mean result which was only 1.4 μg/100 ml. higher than the true cortisol level, and some part of this is accounted for by corticosterone. The precision is approximately ± 1.0 μg/100 ml. and the analytical rate is 20 samples per hour. © 1968.