标准方法(GB 7816-1998)测定黄磷中砷时,采用敞开式消解法预处理样品。实践表明该方法耗时,易引入污染,造成测定误差,而且稍有不慎易使黄磷自燃。作为改进,提出了回流冷凝消解法,即2~3 g试样于硝酸(3+2)溶液60 mL中,在160 ℃电热板上加热回流消解。消解完成后的试液按Ag-DDTC方法进行砷的测定。结果表明:回流冷凝消解法不仅避免了试样的自燃,而且大大缩短了试样消解时间,所测得砷结果的准确度达到原标准方法的水平。

In the determination of arsenic in yellow phosphorus by the GB standard method (GB 7816-1998), the sample pretreatment was carried out by digestion with HNO3 in an open vessel. As happened actually, this method of sample pretreatment had the defects of time-consuming, accidental error due to contamination and unsafety of self-burning of sample. As a modification, sample pretreatment by reflux digestion was proposed, i.e., the sample (2-3 g) was digested with 60 mL of HNO3(3+2) under refluxing at a heating temperature of 160 ℃. After completion of digestion, the sample solution was used for determination of arsenic by the method of the GB standard. It was shown that the defects of the original method of sample digestion did not happened in the refluxing condensation digestion method and in addition, accuracy of analytical results obtained attained to a same level as that of the Ag-DDTC method.