尿样中14C的分析方法

目的 为了完善放射性核素¹⁴C的监测方法，估算¹⁴C对人体造成的内照射剂量，保护¹⁴C暴露行业职工和公众的身体健康。方法 用湿法氧化法对尿样进行前处理。分析时用过硫酸钾作为氧化剂把尿素氧化分解为二氧化碳，并用1 mol/L氢氧化钠吸收后，使吸收液转化为碳酸钙沉淀，碳酸钙粉末悬浮法制样，低本底液体闪烁计数仪检测计数并计算分析结果。结果 用尿素作为载体优化后的反应时间为1 h，对于80 ml尿样，过硫酸钾的使用量为10 g，方法回收率可达到97.15%~102.09%，测量时间300 min时，方法检测下限为0.22 Bq/L。实际检测的4个尿样中，¹⁴C活度浓度分别为0.32、0.60、0.86和0.74 Bq/L。结论 优化后的方法稳定性好，准确度高，能够满足放射卫生工作中¹⁴C日常检测的需求。尿样中¹⁴C定量方法的建立进一步完善了¹⁴C监测的方法体系。

Analytical method for 14C in urine

Objective To improve the analytical method of radionuclide ¹⁴C, and estimate the internal dose caused by ¹⁴C to human, in order to protect the health of workers and the public in workplaces involving potential ¹⁴C exposure. Methods Urine samples were pretreated by wet oxidation. In the analysis, potassium persulfate was used as an oxidant to decompose urea into carbon dioxide, which was absorbed by 1 mol/L sodium hydroxide, and the absorption solution was converted into calcium carbonate precipitation. After calcium carbonate powder was prepared into sample source by suspension method, the low background liquid scintillation counter was applied to measure the radioactivity, which can be used for calculating the result. Results The reaction time optimized by using carbamide as carrier was 1 h. For 80 ml urine, the amount of potassium persulfate used was 10 g. The method recovery rate reached about 100%. Four real urine samples were tested using the optimized method, and the result of activity concentration ¹⁴C was 0.32, 0.60, 0.86 and 0.74 Bq/L, respectively. Conclusions The optimized method had good stability, high accuracy and stable experimental result, which could meet the needs of routine radiological detection. The establishment of a quantitative method for ¹⁴C in urine sample has improved the methodological system for ¹⁴C monitoring.