The determination of captopril (CAP) using a new continuous flow injection analysis (CFIA) method was given in this work CAP in its pure state and some of its pharmaceutical preparations. The technique can be described as simple, fast, sensitive, easy to operate, and low-cost. The CAP reacted with ammonium ceric(IV) sulfate (ACS)2(NH4 )2SO4Ce(SO4)2. 3 H2O in an acidic medium and the reaction led to the formation of a white, slightly yellowish precipitate. The formed precipitate was studied using Ayah 6S×1-ST-2D Solar cell-CFI Analyzer, a through the reflection of accident light on the surfaces of the precipitate particles at (0-1800), expressed as the response of the transducer measured in (mV). Some chemical and physical parameters were studied to provide the optimal conditions for the study. The calibration curve within the range of (0.07-3.0) mmol/L was linear, with a correlation coefficient (r) value equal to (0.9983), and the percentage value of linearity (R2%) was (99.65). The method's detection limit (L.O.D.) of the new method was 272.5 ng/25 µL; it was calculated by diluting the minimum concentration in the calibration curve gradually. RSD% was less than 0.2% for 0.9, 1.5, and 3.0 mmol/L concentrations of C.A.P. for n=8. The method was successfully applied to estimate C.A.P. in three pharmaceutical preparations, each produced by a different company. The new method was compared with the UV-Spectrophotometric method (classical method) at λmax= 207.2 nm by using the method of standard additions. Both the t-test and the F-test were conducted to ensure that there wasn't a significant difference between the new method and the conventional one. The results of both tests showed, at a confidence level of 95%, that there was no significant difference.
