Flow‐injection chemiluminescence method for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride

A sensitive and simple flow‐injection chemiluminescence (FI‐CL) method, which was based on the CL intensity generated from the redoxreaction of potassium permanganate (KMnO 4 )–formaldehyde in vitriol (H 2 SO 4 ) medium, has been developed, validated and applied for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride. Besides oxidants and sensitizers, the effect of the concentration of H 2 SO 4 , KMnO 4 and formaldehyde was investigated. Under the optimum conditions, the linear range was 1.0 × 10 −2 –7.0 mg/L for naphazoline hydrochloride and 5.0 × 10 −2 –10.0 mg/L for oxymetazoline hydrochloride. During seven repeated inter‐day and intra‐day precision tests of 0.1, 1.0 and 10.0 mg/L samples, the relative standard deviations all corresponded to reference values. The detection limit was 8.69 × 10 −3  mg/L for naphazoline hydrochloride and 3.47 × 10 −2  mg/L for oxymetazoline hydrochloride (signal‐to‐noise ratio ≤3). This method has been successfully implemented for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride in pharmaceuticals. Copyright © 2009 John Wiley & Sons, Ltd.