Separation of thiosulfate and the polythionates in gold thiosulfate leach solutions by capillary electrophoresis

Abstract

A technique for the separation of thiosulfate (S(2)O(3) (2-)), polythionates (S(x)O(6) (2-), x = 3 to 5) and the gold(I) thiosulfate complex (Au(S(2)O(3))(2) (3-)) using capillary electrophoresis with simultaneous UV detection at 195 and 214 nm is presented. The five species were separated in under 3 min with a total analysis time of 8 min, using an electrolyte containing 25 mM 2,2-bis(hydroxymethyl)-2,2',2"-nitrilotriethanol (bis-tris) adjusted to pH 6.0 with sulfuric acid and an applied voltage of -30 kV. While the gold(I) thiosulfate complex could be separated from the other analytes of interest under these conditions, the quantification of this complex was not possible due to inconsistent peak areas and peak splitting effects induced by the sulfur-oxygen species in the leach matrix. Detection limits calculated for 3s pressure injection at 50 mbar ranged between 0.5-2 microM. The method was linear over the ranges 40-8000, 10-2000, 10-2000, and 5-2000 microM for thiosulfate, trithionate, tetrathionate, and pentathionate, respectively. The technique was applied successfully to leach liquors containing 0.5 M ammonium thiosulfate, 2 M ammonia, 0.05 M copper sulfate and 20% w/v gold ore, diluted 1:100 prior to analysis.

The Importance of Thiosalts Speciation: Review of Analytical Methods, Kinetics, and Treatment

“…In a study to separate gold thiosulfate leach solutions using capillary electrophoresis (O'Reilly et al, 2003) complex formation of gold thiosulfate, reactions between the sulfur oxyanions as well as high ionic strength of samples were issues which needed to be addressed in order to obtain reliable analytical results. Capillary electrophoretic analysis also requires low concentrations of samples in order to get a good dynamic range for quantification of analyte concentrations.…”

Capillary electrophoresis of inorganic ions: An update

“…8) [107,119] and neptunium oxidation states [107]. Much research continues on improving speciation measurements in real-world samples, with advanced CE procedures tailor-made to the analysis of natural [94,95,156,157,160,161,168,173,187,249,250] and waste waters [79,94,95], soil solutions or extracts [78,104], air [253], minerals [245], industrial samples and technological solutions [83,189,190,198,233,235,236,254,256], pharmaceutical preparations [199,248,255], biological material [102,118,175,231,251,252], food [224], and animal feed [211], etc. In particular, an innovative methodology for the automatic monitoring of mercury species in aquatic samples was suggested by Valcárcel's group [237].…”

Investigation of the factors that induce analyte peak splitting in capillary electrophoresis

“…O'Reilly et al [3] reported that peak splitting effects were induced by the sulfur-oxygen species in gold thiosulfate leachate solutions. The electrolyte contained 25 mM bistris and was adjusted to pH 6.0 with H 2 SO 4 .…”