A Study of the Effect of pH on the Determination of Zinc by Atomic Absorption Spectrophotometry

Abstract

Substantial errors in the determination of zinc by atomic absorption spectrophotometry can be caused by differences in pH among samples and standards. Zinc absorption is constant in the pH range of about 2 to 5. Between pH 5 and 10, a sharp decrease in absorption is observed. With an increase above pH 10, zinc absorption levels off to a constant value. Experimental data suggested that pH variation rather than chemical interferences is primarily responsible for the variation of absorption in zinc analysis. Several possibilities, such as sorption of zinc to container walls, zinc hydroxide formation, zinc complex formation, and zinc oxide formation in flame subsequently attacked by hydrogen atoms, have been considered in an attempt to understand the cause of pH-dependent zinc absorption.