氢化物发生原子荧光法测定钢铁中微痕量碲

碲是钢铁的微痕量有害杂质，易引发晶间脆化和微裂纹，降低材料的力学与抗疲劳性能，危及船海装备的服役安全，需要准确快速的检测和控制。原标准方法GB/T 223.55—2008《钢铁及合金 碲含量的测定 示波极谱法》使用滴汞电极，存在局部汞富集与危及人员健康和水体环境的风险。伴随《关于汞的水俣公约》在国内外的全面生效，该方法已于2017年废止。钢铁中碲的检验迫切呼唤绿色环保、准确快速的分析方法。基于碲可被新生态氢还原为易挥发氢化物的特点，采用氢化物发生进样技术从基体溶液中高选择性地分离和富集碲，并联用原子荧光法测定钢铁中微痕量碲。实验优化了负高压、灯电流、观察高度、载气流量、屏蔽气流量等光谱仪的工作参数，研究确定了消解用酸、试液介质、溶液酸度、载流酸度与硼氢化钾浓度等氢化物发生条件，系统考察了铁基体与铬、镍、锰、铜、钼、钨、钛、硅、钒等共存离子的干扰效应及掩蔽方法。确定的条件参数如下，负高压：360 V，灯电流：70~80 mA，观察高度：7~8 mm，载气流量：700 mL·min-1，屏蔽气流量：700~800 mL·min-1，试液介质：15%盐酸，掩蔽剂：2%硫脲-抗坏血酸，硼氢化钾浓度：1.5%~2.5%。称取0.080 g钢铁试样，加入3.00 mL王水低温加热至溶解完全，加入20.00 mL 10%硫脲-抗坏血酸混合溶液，并用15%盐酸定容至100 mL。采用基体匹配法，以铁基体溶液建立校准曲线，校准曲线呈二次方程，相关系数为0.999。方法的定量限为1.25 μg·g-1，测定结果的相对标准偏差（RSD）不大于7%，合成样品的测定结果与理论值相符，偏倚小于GB/T 223.55—2008规定的允许差。该方法具有灵敏、准确、快速、绿色的优点，可用于船海用钢中微痕量碲的检测。

Determination of Trace Tellurium Content in Steel by Hydride Generation Atomic Fluorescence Spectrometry

Tellurium was a trace and harmful impurity element in iron and steel materials, which could reduce the mechanical and fatigue properties of materials by causing embrittlement and micro-cracks between crystals, and further endanger the service safety of marine equipment. Therefore, it was important to accurately and quickly determine and control tellurium in steel. The original standard method GB/T 223.55—2008《Iron, steel and alloy—Determination of tellurium content-Oscillo-polarographic method》 was abolished in 2017, with the full international and domestic entry into force of the Minamata Convention on Mercury. Because the above method used the dangerous dropping mercury electrode, which would cause the accumulation of mercury in the local environment, thereby endangering the operator’s health and water environment, the analysis of tellurium in steel urgently needed a more environmentally friendly, accurate and rapid method. Based on the characteristics that tellurium could be reduced to volatile tellurium hydride by new ecological hydrogen, the hydride generation sampling technology was used to separate and enrich tellurium from the matrix solution with high selectivity, and the atomic fluorescence method was used in parallel to determine the trace tellurium content in the steel. The working conditions of the atomic fluorescence spectrometer have been optimized, such as negative high voltage, lamp current, observation height, carrier gas flow, the shielding gas flow. Moreover, hydride generation conditions have been studied, including digestion acid, test solution medium, solution acidity, carrier flow acidity and potassium borohydride concentration. Then, the background interference of steel matrix with coexisting ions such as chromium, nickel, manganese, copper, molybdenum, tungsten, titanium, silicon, and vanadium, and the masking methods were systematically investigated. The optimized condition parameters were as below: negative high voltage of 360 V, lamp current of 70~80 mA, observation height of 7~8 mm, carrier gas flow of 700 mL·min-1, shielding gas flow of 700~800 mL·min-1. The test solution medium was 15% hydrochloric acid, the masking was 2% thiourea-ascorbic acid, and the potassium borohydride concentration was 1.5%~2.5%. The 0.080 g steel sample was digested by 3 mL aqua regia at low temperature until completely dissolved. Then 20.00 mL 10% thiourea-ascorbic acid mixed solution was added, and the volume was adjusted to 100 mL with 15% hydrochloric acid. A calibration curve was established with iron the matrix solution based on matrix matching method. The calibration curve was a quadratic equation with a correlation of 0.999. The limit of quantification was 1.25 μg·g-1, and the relative standard deviation of the determination result was not more than 7%. The determination results of the simulated sample were consistent with the theoretical value, and the bias was better than the tolerance specified in GB/T 223.55—2008. The proposed method has the advantages of sensitivity, accuracy, speed and greenness and could be used for the inspection and control of trace tellurium in steel for marine engineering.