紫外脉冲荧光法测定锆英砂中铀含量

以氟氢化钾熔融样品, 熔样温度由低温升至900 ℃, 使矿物晶体结构破坏, 然后用氢氟酸、硫酸继续溶解矿物以彻底分解锆英砂矿物。试液中的铀酰络合物在被紫外脉冲激发后产生铀的荧光与浓度呈正比, 由此实现用紫外脉冲荧光法对锆英砂中铀的直接测定。研究了紫外脉冲荧光法的影响因素, 并确定了下面最佳测定条件:试液的温度保持在13～20 ℃, 测定时试液的pH值为7, 采用标准加入法测定, 加标溶液为0.5 μg/mL的铀标准溶液。对共存元素的干扰进行了试验, 结果表明, 测定0.001 mg铀, 当测定结果的相对误差在±5%范围时至少2.5 mg Zr, 0.8 mg Si, 0.065 mg Hf, 0.007 5 mg Ca²⁺、Al³⁺, 0.75 μg Mn²⁺, 0.015 μg Eu²⁺、Dy³⁺不干扰, 大于 0.002 5 mg铁产生的负干扰, 但可以通过适当稀释溶液的方法消除。用拟定的方法对英国化学标准物质(BCS 388、SARM13和SARM62锆英砂)中铀进行测定, 测定值与认定值一致。

Determination of uranium in zircon sand by ultraviolet pulse-induced fluorescence method

Potassium hydride fluoride was used to fuse sample from low temperature to 900 ℃ in order to fracture mineral crystal structure , then hydrofluoric acid and sulfuric acid were used to decompose the sample thoroughly. After the uranyl complex in the sample was excited by the UV pulse, the fluorescence intensity of uranium was proportional to the concentration. Accordingly, a direct determination of uranium in zircon sand by UV pulse-induced fluorescence method was established. The influence factors of the method were studied and the optimal working conditions were selected as follows: the sample solution temperature should be keep at 13-20 ℃; the pH of the sample solution should be controlled at 7; the standard addition solution concentration should be 0.5 μg/mL uranium standard solution when standard addition method was used. Besides, the interference of coexisting elements was tested. It was found that, within relative error of ± 5 %, the determination of 0.001 mg of uranium was not affected by 2.5 mg of Zr, 0.8 mg of Si, 0.065 mg of Hf, 0.007 5 mg of Ca²⁺ and Al³⁺, 0.75 μg Mn²⁺, 0.015 μg of Eu²⁺ and Dy³⁺, but iron more than 0.025 mg would produce negative interference which could be eliminated through solution dilution method. The method was used to determined uranium in British chemical standard BCS 388, SARM 13 and SARM 62. The results were consistent with the certified values.