Abstract
Sequential injection analysis (SIA) technique and chemometric optimization were employed, for the first time, to develop a new method for the assay of diltiazem in pharmaceutical formulations. The method was based on the spectrophotometric detection of permanganate reduction by diltiazem in acidic media at 526 nm. The 2(3) full factorial design and response surface plot were adopted to optimize permanganate concentration, acid concentration and flow rate. The method was validated as per the International Union of Pure and Applied Chemistry (IUPAC) guidelines. Relatively, wide Beer's law limit (10-180 mg/L) with satisfactory linearity (correlation coefficient = 0.9996) and recovery (95.4-98.1%) were obtained. The method also recorded good repeatability (RSD = 1.19-1-64%, n = 10) and intermediate-precision (2.84%, n = 5, once per a day). The method is sensitive enough for determining diltiazem in pharmaceutical formulations with limits of detection (1.30 mg/L) and quantification (3.94 mg/L). The method is rapid with sample frequency of 32 sample/h. The method was applied to real pharmaceutical samples and the results obtained were realized by parallel analysis by another validated method. The method enjoys the potentials of SIA and chemometric optimization with respect to good accuracy, precision, sensitivity and rapidity. The method is also inexpensive in terms of instrumentation as well as the consumption of reagents and samples. Besides good safety for handling solutions, the SIA technique offers significant waste minimization and manpower reduction to the proposed method. Therefore, the SIA method is suitable in pharmaceutical laboratory for quality control purpose.