Development of Spectrophotometric Method to Assay Phenylephrine Hydrochloride in Pure and in its Pharmaceutical Forms Using Diazotized Sulphanilic Acid

This work described a simple and sensitive spectrophotometric procedure for estimating phenylephrine hydrochloride in pure and in its pharmaceutical using diazotized sulphanilic acid as a coupling agent in alkaline medium of sodium carbonate solution. The resulting yellow azo-dye displayed an absorption maximum at 441 nm. The calibration graph was linear and compatible to Beer's law over the concentration range 0.2-20 µg/mL with coefficient estimated (r2=0.9996). The values of molar absorptivity and the sensitivity of Sandell's index were calculated and equal to 8.51×103 l/mol.cm and0.0239 µg/cm2, respectively. The values of detection limit (LOD), quantification limit (LOQ) and the range of relative error percentage were estimated and found to be 0.0050, 0.0166 µg/mL and -0.374% to -0.147%, respectively. The precision (represented by RSD) was also calculated and found to be in the range ±0.037 to ±0.28. The suggested procedure was useful successfully to the assay of phenylephrine hydrochloride in injection, drops and syrups. No interferences were observed from common additives found in pharmaceutical preparations. The yellow color of the product was highly stable and did not show a significant change in absorbance up to 60 min