砷化氢分离-砷钼蓝分光光度法测定铁矿石中砷的国家标准方法探析

Research on national standard method for the determination of arsenic in iron ore by hydrogen arsenide separation-arseno-molybdenum blue spectrophotometry

对铁矿石砷含量测定的国家标准方法——砷化氢分离-砷钼蓝分光光度法的关键步骤和要点,如锌粒粒度、砷化氢气体导管插入吸收液深度、吸收管的干燥等进行探析。表明锌粒的粒度与砷化氢气体发生的反应时间有关,反应时间在40 min内应采用≤3 mm锌粒,反应时间在60 min时,采用4-5 mm锌粒对测定结果没有影响;砷化氢导管的插入深度和吸收管的干燥情况对测定结果有影响,砷化氢导管的插入深度在4-8 cm和使用干燥的吸收管可以得到稳定的结果。用两个铁矿石标准样品对上述条件进行验证,测定值与认定值吻合,相对标准偏差（RSD）小于2%。此外,对样品分解方式、波长、校准曲线的绘制、还原剂等提出改进意见,拓宽了方法的适用性和可选择性,满足实际生产中量大而快速的检测需要。

The key steps and main points of the national standard method for the determination of arsenic in iron ore by hydrogen arsenide separation-arseno-molybdenum blue spectrophotometry were discussed including granularity of zinc,the insertion depth of hydrogen arsenide gas catheter in absorption solution and the drying of absorption tube.It was shown that the granularity is related with the reaction time of hydrogen arsenide gas.For the purpose of avoiding affecting the determination results,zinc smaller than 3 mm should be used for reaction within 40 min,while zinc of 4-5 mm should be used for reaction of 60 min.The insertion depth of hydrogen arsenide catheter and the drying state of absorption tube would affect the determination results.When the catheter was inserted 4-8 cm,stable results could be obtained with dry absorption tube.On the basis of these,two iron ore standard samples were analyzed.The determination results were consistent with the certified values,and the relative standard deviation was smaller than 2 %.In addition,some improvement advices such as sample decomposition method,wavelength,the plotting of calibration curve and reducing reagents were proposed in order to broaden the applicability and selectivity of the method.The proposed method could meet the demand for rapid determination of batch samples in actual production.