Simultaneous Determination of Paracetamol and Cephalexin Binary mixtures by Using Derivative Spectrophotometry and H-point Standard Addition Methods

Abstract

Two methods are applied for simultaneous determination of paracetamol (para) and cephalexin (ceph) in combined mixtures, derivative spectrophotometric technique and H-Point standard addition method (HPSAM) spectrophotometry. The first procedure is based on the use of the, second derivative ( 2D ) and used the suitable wave lengths at zero crossing at valley 250.5 and 290.2 nm for determination paracetamol and cephalexin respectively.. Calibration graphs were established for 2-60 mg/L for Para and 2-70 mg/L for ceph in binary mixture. The proposed method were successfully applied to the determination of these drugs in synthetic mixtures, linearity was excellent (r2>0.999) over the concentration tested (2–60 mg/L) with good precision and accuracy. Recoveries were good (>98%) with limits of detection of 1 and 1.5 mg/L ,(%R.S.D.= 0.757 - 1.207) for para and ceph, respectively.. The second procedure HPSAM was applied to the simultaneous determination of Para and ceph. respectively. (HPSAM) method was based on the difference in the absorbance of para and ceph.at choosing wavelengths (265 and 257 nm). Results of the analysis of the different mixtures in the proposed system revealed a dynamic range of 2-35 and 2-50 mg/L, with limits of detection of 2 and 3 mg/L for para and ceph, respectively. The relative error are between -0.605-1.64 and -1.230-1.43, for para and ceph respectively. RSD% 0.151-1.775 for para and ceph, respectively. The two methods were found to be precise, accurate, simple and rapid.