Determination of Gold in High-Antimony Rocks and Minerals by Flame Atomic Absorption Spectrometry with Hydride Generation Separation to Eliminate Antimony Interference

Gold is a globally critical and scarce mineral resource. High-antimony rocks and minerals are important carriers of gold mineralization, where gold usually occurs as fine-grained native gold, sulfide-bound gold, or encapsulated gold, and high antimony content seriously interferes with the accurate determination of gold. Existing methods cannot simultaneously solve the three core difficulties of “no encapsulation loss of gold”, “stable and efficient reduction system” and “complete removal of antimony”, which restricts the accurate evaluation and efficient development of such resources, and the core scientific problem is how to achieve complete removal and stable reduction of antimony while avoiding gold loss. To address this problem, this paper proposes a strategy of “stepwise roasting, reduction transformation, and hydride generation separation”, clarifies the nature of interference through a series of experiments, uses stepwise roasting to avoid encapsulation of gold particles, completely converts antimony to Sb(Ⅲ) in the thiourea-ascorbic acid composite system, and determines the gold content by flame atomic absorption spectrometry (FAAS) combined with dynamic enrichment with activated carbon. Verification with reference materials and actual samples shows that when the antimony content is higher than 18%, the sample sinters during roasting; when the antimony content in the solution is more than 60 mg (6%), it interferes with gold analysis; the optimal antimony removal conditions are 1.5 g of potassium borohydride (15% concentration, 10 mL dosage), with both antimony removal rate and gold recovery rate ＞95%; the detection limit of gold is 0.028 μg/g, and the detection range is 0.12–50 μg/g; the relative errors of reference material determination are 1.75%–2.32%, and the RSDs are 2.70%–3.58%, which are better than those of the national standard method; the spiked recovery rates of actual samples are 97.2%–102.3%, and the t-test values are all ＜2.571, meeting the requirements of Specification for Testing Quality Management of Geological and Mineral Laboratories (DZ/T 0130—2006). This method can effectively eliminate antimony interference and provide a reference for the analysis of precious metals in similar interference matrices.