IMPROVED AUTOMATIC KINETIC METHOD FOR THE DETERMINATION OF VARIOUS CORTICOSTEROIDS

Two reaction-rate methods for the determination of corticosteroids at the micromolar level were developed. The methods are modifications of the widely used Blue Tetrazolium and Porter-Silber reactions which are employed for the automatic kinetic determination of corticosteroids u sing the continuous-addition-of-reagent (CAR) technique. The CAR techn ique avoided all technical problems typically associated with these re actions such as long incubation at high temperatures, high blank value s, and turbidity. On the basis of its analytical figures of merit, the Blue Tetrazolium method was chosen; it allows corticosteroids to be d etermined at concentrations from 2.7 X 10(-6) to 1.9 X 10(-4) M at a r ate of 25 samples/h (triplicate analyses) with an root mean square dev iation of ca. 3%. The proposed method was evaluated in recovery experi ments and analyses of commercially available formulations.