Spectrophotometric determination of cations in presence of surfactants III. determination of zinc [II] using some AZO and xanthene reagents

ABSTRACT

A sensitive spectrophotometric method for zinc [II] has been established by reacting zinc with sulphochlorophenol S [I] and pyrogallol red [II] in buffer solutions of pH 8.4 and 9.4 for the two reagents respectively, either in absence or presence of hexadecylpyridinium chloride. The molar absoroptivities are 1.2 and 1.9; and 1.61, 5.39, 2.31 and 3.58x10[4] 1 mol[-1]. Cm[-1] at 665, and 722 for sulphochlorophenol S, 600; 302, 630, and 316 nm for pyrogallol red using reagents I and II, respectively. Beer's law is obeyed over 0.2-6.0 g.ml[-1]. Sandell sensitivities of the methods are evaluated. The formed complexes have the molar ratios of zinc [II] ligand 32 and 37 for reagents I and II respectively, whereas the stability constant for the formed complexes are calculated and the -log stability constant recorded. LOD are 0.025 and 0.0491 for reagent [I], 0.0356, 0.1098, 0.0708 and 0.0408 for reagent [II]. X +/-S.D. are 100.97 +/-1.17 and 100.04 +/-0.191 for reagent [I], 99.94 +/-0.733, 99.98 +/-0.213, 100.8 +/-0.325 and 100.13 +/-0.233 for reagent [II]. Statistical analysis of the results obtained compared to the results obtained by the atomic absorption spectrophotometric method revealed equal precision and accuracy. The suggested procedure was applied for determining zinc [II] in pharmaceutical preparations and proved high validity