Colorimetric Flow Injection Determination of Resorcinol-Type β2-Adrenergic Drugs with Phenanthro[9, 10-d]imidazole-2-N-chloroimide

A simple and rapid flow injection method has been developed for the colorimetric determination of resorcinol-type β2-adrenergic drugs: fenoterol hydrobromide, orciprenaline sulfate and terbutaline sulfate, by using phenanthro-[9, 10-d]imidazole-2-N-chloroimide (Pl-NCl) as a color reagent. The color reaction between the drugs and Pl-NCl occurs at alkaline pH. Under the optimized conditions, the calibration curves for the three drugs were linear over the range of 0.5-200μM. The relative standard deviations (n=10) for fenoterol hydrobromide, orciprenaline sulfate and terbutaline sulfate were 1.7, 1.4 and 1.0%. The present method was applied to the determination of those drugs in commercial formulations.