Methods compared for determining zinc in serum by flame atomic absorption spectroscopy

Abstract

We compared two methods for determination of serum zinc by flame atomic absorption spectroscopy. The first involved 10-fold dilution of serum with water; the second, deproteinization of serum with trichloroacetic acid. Analytical recovery of Zn2+ added to serum averaged 99.3 and 99.9%, respectively, by the two methods, but measured concentrations were consistently greater by the second method [mean difference, 118 +/- 27 (SD) mug/liter]. For the analysis of 55 sera, measured concentrations were also greater by the second method [mean difference, 91 +/- 28 (SD) mug/liter]. We dialyzed serum to remove most of the zinc and measured analytical recovery of increasing amounts of Zn2+ added to this dialyzed serum or, conversely, of zinc in a mixture of increasing volumes of dialyzed serum in a Zn2+ standard. Recovery results for the dilution method showed an interference by an unidentified, but nondialyzable serum component(s). Recovery was not improved by use of (a) a "high-solids" burner, (b) a diluent containing 1-butanol, or (c) a Mn2+ internal standard.