Flow injection chemiluminescence determination of captopril based on its enhancing effect on the luminol–ferricyanide/ferrocyanide reaction

A new flow injection chemiluminescence method is described for the determination of captopril. It is based on the enhancing effect of captopril on the chemiluminescence reaction of luminol with potassium ferricyanide in alkaline solution in the presence of potassium ferrocyanide. The method allows the determination of captopril over 0.1-40 microg/mL range, with a relative standard deviation (SD) of 1.0% for the determination of 0.5 microg/mL captopril solution in 11 repeated measurements. The method was satisfactorily applied to the determination of captopril in commercial captopril tablets. The possible reaction mechanism is also discussed briefly.