Spectrophotometric flow injection system for determination of Zn2+ in ophthalmic formulations using Alizarin red S

Orlando Fatibello-Filho,Heberth Juliano Vieira

doi:10.26850/1678-4618eqj.v34.2.2009.p67-72

Abstract

A spectrophotometric flow injection method for the determination of Zn(II) in ophthalmic formulations was developed. In this work, Zn(II) ion was complexed with Alizarin red S in borate buffer solution (pH 9.0) and the chromophore produced was monitored at 520 nm. The analytical curve was linear in the Zn(II) concentration range from 6.05 x 10-6 to 1.50 x 10-4 mol L-1 with a detection limit of 3.60 x 10-6 mol L-1. Recoveries ranged from 96.3 to 105 % and a relative standard deviation of 1.2 % (n = 10) for 5.5x10-5 mol L-1 Zn(II) reference solution were obtained. The sampling rate was 60 h-1 and the results obtained of Zn(II) in ophthalmic products using this procedure are in close agreement with those obtained using a comparative spectrophotometric procedure at 95 % confidence level.

Highlights

Zinc compounds have bactericidal activity since they can precipitate and denature several bacterial proteins
The USP XXIII Pharmacopoeia recommends the determination of Zn(II) by atomic absorption spectrometry (AAS) or by an extractive spectrophotometric method [3]
Several spectrophotometric procedures reported in the literature for the determination of Zn(II) are summarized by Bhalotra et al.[4] and a previous solvent extraction step is required in other spectrophotometric methods [5,6,7,8,9]

Summary

Introduction

Zinc compounds have bactericidal activity since they can precipitate and denature several bacterial proteins. A multicommutation flow procedure [23] and a sequential injection analysis system [20] were described for the determination of Zn(II) in pharmaceutical formulations In this work we present a simple flow injection method for determining Zn(II) in pharmaceutical solutions based on the formation of a water When a 250 μL (50 cm) sample volume containing Zn2+ reference or sample solution was injected, occur the formation of the soluble complex between Alizarin red S and Zn2+ in the reactor coil (150 cm), which was monitored spectrophotometrically at 520 nm.

Results

Conclusion