Spectrophotometric Determination of Primaquine by Coupling with Diazotized p-Nitroaniline Application to Pharmaceutical Formulations

A simple spectrophotometric method for the determination of primaquine phosphate has been developed. The method is based on the coupling reaction of primaquine phosphate in acidic medium with diazotized p-nitroaniline, to form a yellow-orange water-soluble azo dye that shows maximum absorption at 482 nm. Beer’s law is obeyed over the concentration range 5-300 μg of primaquine phosphate in a final volum of 25 ml, i.e., 0.2-12 ppm with a molar absorptivity of 6.6 104 l mol-1 cm-1 and Sandell’s sensitivity index of 0.0068 μg.cm-2, a relative error of -0.63 to +0.32% and a relative standard deviation of ±0.18 to ±2.8%, depending on the concentration level. Interferences due to excipients have been examined. The proposed method has been applied to the assay of primaquine phosphate in pharmaceutical formulations (tablets).