Spectrophotometric Determination of Phenylephrine Hydrochloride by Coupling with Diazotized 2- Aminobenzothiazole

A spectrophotometric method for determination of microgram amounts of phenylephrine-HCl(PE) has been proposed. The method is based on coupling of phenylephrine-HCl with diazotized 2-aminobenzothiazole in alkaline medium. The molar absorptivity of the formed dye is 6.620×10 3 l.mol -1 . cm -1 at λ max 510 nm and Beer ' s law obeyed within in the range of 10-250 μg of phenylephrine-HCl /25 ml (0.4 – 10 ppm). The colour reaction was highly stable and did not show a significant change in absorbance(within acceptable analytical error) up to 48 h with a relative error +0.31 to +1.07% and a relative standard deviation of ±0.95 to ±3.09%, depending on concentration level. The method has been applied successfully to the determination of phenylephrine-HCl in pharmaceutical preparation (nose drop) .