分光光度法测定多晶硅中铁和铝

Determination of iron and aluminum in polycrystalline silicon by spectrophotometry

将多晶硅（硅粉）用氢氟酸和硝酸二次溶解,用高氯酸的二次冒烟去除氟离子对铝的干扰,用3 cm的比色皿解决铁低灵敏度带来的误差大的问题。使用分光光度法准确测定多晶硅中铁和铝的含量。研究了显色条件对显色反应的影响,确定最佳实验条件。结果表明,在pH3～5的乙酸-乙酸钠缓冲溶液中,铁与5 mL 0.25 g/L的1,10-二氮杂菲10 min后生成稳定的红色络合物,且在2～10μg/50 mL范围内服从比尔定律;在pH 5.5～6.1的六次亚甲基四胺缓冲溶液中,铝与5 mL 0.3 g/L的铬天青-S在15 min后形成稳定的紫红色络合物,且在4～16μg/50 mL范围内服从比尔定律。用分光光度法能准确测定纯度为99.99%多晶硅（硅粉）中铁和铝含量,并与ICP-AES法测试结果对比,相对误差在5%左右。

The polycrystalline silicon（silica powder） was double dissolved with hydrofluoric acid and nitric acid.The interference of fluorinion with aluminum was eliminated by double smoking of perchloric acid.The great error caused by low sensitivity of iron was solved by using 3 cm cuvette.The content of iron and aluminum in polycrystalline silicon were accurately determined by spectrophotometry.The effect of coloring conditions on coloring reaction was investigated to obtain the optimal experimental conditions.The results showed that in HAc-NaAc buffer solution at pH 3-5,Fe^2＋ could form a stable red complex with 5 mL of 1,10-phenanthroline（0.25 g/L） after 10 min and Beer＇s law was obeyed for iron in the range of 2-10 μg/50 mL.In hexamethylenetetramine buffer solution at pH 5.5-6.1,the Al^3＋ could form a stable purple-red complex with 5 mL of chromeazurol-S（0.3 g/L） after 15 min,and Beer＇s law was obeyed for aluminum in the range of 4-16 μg/50 mL.The content of iron and aluminum in polycrystalline silicon（silica powder） with purity of 99.99% could be accurately determined by spectrophotometry.The determination results were compared with those obtained by ICP-AES.The relative error was about 5 %.