金-溴酸钾-番红花红O阻抑动力学光度法测定痕量金

在磷酸介质中,痕量金对溴酸钾氧化番红花红O的变色反应有很强的抑制作用,据此,建立了阻抑动力学光度法测定痕量金的新方法。实验表明,在两支25 mL比色管中分别加入0.6 mL 1.0 g/L番红花红O溶液、0.5 mL 6.0 mo1/L磷酸,其中一支加适量金(阻抑体系),另一支不加(非阻抑体系),再分别加 0.7 mL 0.05 mo1/L溴酸钾溶液,定容至10 mL,在100 ℃水浴中反应20 min,于波长520 nm处测定阻抑和非阻抑体系的吸光度差,金的浓度在0.5～6 ng/mL范围内与ΔA呈良好的线性关系。方法检出限为7.62×10^－12g/mL,表观活化能为74.97 kJ/mol。方法用于矿石中金的测定,测得结果与原子吸收光谱法一致,相对标准偏差(RSD, n=6)为3.1%~3.5%,回收率为99%～105%。

Determination of trace gold by inhibitory kinetic spectrophotometry with gold-potassium bromate-safranine O system

In phosphoric acid, trace gold  exerted strong inhibitory effect on the color changing reaction of safranine O oxidized by potassium bromate. Based on these phenomena, a new inhibitory kinetic spectrophotometric method was established for the determination of trace gold . The experiment indicated that two 25 mL colorimetric tubes were added into 0.6 mL of 1.0 g/L safranine O solution and 0.5 mL of 6.0 mol/L phosphoric acid, respectively. Trace gold was added into one tube (inhibitory system), but not added into another (non-inhibitory system). Then, 0.7 mL of 0.05 mol/L potassium bromate was added into both tubes. After dilution to 10 mL, the tubes were heated in water bath at 100 ℃ for 20 min. The absorbance difference (ΔA) between inhibitory system and non-inhibitory system was measured at 520 nm. The results showed that ΔA exhibited good linearity to the concentration of gold in range of 0.5-6 ng/mL. The detection limit of method was 7.62×10^－12 g/mL and the apparent activation energy was 74.97 kJ/mol. The proposed method was applied to the determination of gold in ore. The results were consistent with those obtained by atomic absorption spectrometry. The relative standard deviation (RSD, n=6) was 3.1%-3.5%, and the recoveries were between 99% and 105%.