Rapid and Sensitive Online Determination of Some Selective I-1-Blockers by Flow Injection Analysis with Micelle-Enhanced Fluorescence Detection

A rapid, sensitive and selective flow injection analysis (FIA) method was developed for the determination of some selective I-1-blockers including; terazosin (TER), doxazosin (DOX), prazosin (PRZ), and alfuzosin (ALF). The method was based on enhancement of the native fluorescence of the studied drugs in the presence of sodium dodecyl sulfate (SDS). The method was optimized for the buffer type, concentration and pH, surfactant type and concentration, flow rate and detection wavelengths in order to achieve the maximum sensitivity. The results showed that the best sensitivity was obtained by using SDS (10 mM) in phosphate buffer (20 mM, pHa=a3), flow rate was 0.5 ml/min and the detector was set at I>exa=a250 and I>ema=a389. Under these optimum conditions there was a linear relationship between the concentration and the fluorescence intensity in the range from 5a400 ng mla with correlation coefficient of more than 0.998. The detection and quantitation limits for the studied drugs by the proposed method were 3.2a11.9 ng mla1 and 10.8a39.7 ng mla1, respectively. The method was validated in accordance with the requirements of ICH guidelines and shown to be suitable for intended applications. Moreover, the binding constants for I-1ablockers aSDS system were determined using the adduct model. The proposed method has been applied successfully for the analysis of the pure forms for studied drugs and also their pharmaceutical formulations and the results were compared with official methods.