Analysis for sulfur as hydrogen sulfide incorporating zirconia pretreatment and preconcentration

The method of analysis for sulfate by reduction of high oxidation state sulfur to hydrogen sulfide, followed by spectrophotometric analysis, has the advantages of allowing small quantities to be measured and some interfering species to be removed. However, it has been found that acid digested samples cannot be analysed by this method due to destruction of the reduction mixture. A column of zirconium(IV) oxide was successfully used to both, remove interfering ions (H(+), Cl(-) and NO(-)(3)) from a sediment digest, as well as perform preconcentration of sulfate. Recoveries from digests of standard sulfur samples were 101 +/- 1%, and from preconcentration solutions 98.8 +/- 1.2%. Comparison of results with independent analyses confirmed that not all sulfur species are detected with the same efficiency by the combined zirconia/reduction-spectrophotometric method.