Determination of trace amounts of gold in acid-attacked environmental samples by atomic absorption spectrometry with electrothermal atomization after preconcentration.

A method for determination of trace amounts of gold in environmental samples (rocks, soils, sediments, and waters) by atomic absorption spectrometry with electrothermal atomization (ETAAS) after preconcentration using a chelating sorbent Spheron Thiol 1000 is described. The method accurately determines gold between 0.001 and several tens of grams per ton in samples having complex variations in mineralogy. Pulverized samples are roasted at 650 degrees C to oxidize any sulfide and/or carbonaceous material. Samples are then subjected to a series of acid treatments to eliminate any silica matrix and to dissolve the sample. The Spheron Thiol 1000 is added to the sample solution, and then with sorbed gold is filtered out, washed, and ignited at 550 degrees C. The residue is dissolved in aqua regia, evaporated, dissolved in distilled water, transferred to a volumetric flask, and analyzed by ETAAS. The limits of detection of gold, based on the 3 sigma definition, were 0.5 ng g(-1) for 10-g samples (rocks, sediments, soils) and 0.05 ng mL(-1) for 1-L water samples. Precision of determination expressed by the relative standard deviation varied from 2.9% to 16.4%. The accuracy of the method is verified by analysis of certified reference materials. The obtained analytical results are in good agreement with attested values. The developed method was applied for gold determination in environmental samples affected by the acidification (acid mine drainage which is mainly a product of pyrite oxidation) from an open quartzite mine in the Sobov region situated NE of the city of Banská Stiavnica (Slovakia).