铝-氟-邻羟基苯芴酮-吐温-20多元反应体系用于光度法测定痕量铝

Photometric Determination of Trace Amount of Aluminum by the Multi-componental Reaction System of Al(Ⅲ)-F^--o-HPF-Tween-20

基于反应体系条件的研究,提出了灵敏度较高的测定痕量铝的光度法。在含铝(Ⅲ)的试液中,先后加入50 g.L-1氟化钾溶液4 mL,50 g.L-1吐温-20溶液2 mL,氨水-氯化铵缓冲溶液(pH9.5)4 mL及500 mg.L-1邻羟基苯芴酮(o-HPF)溶液2.0 mL使反应生成铝(Ⅲ)与o-HPF的络合物。在此反应体系中F-离子作为铝(Ⅲ)的辅助络合剂,吐温-20则对显色反应兼有增溶及增敏作用。若干共存金属离子[钛(Ⅵ)除外]的干扰可在加入氟化钾之后加入20 g.L-1EDTA溶液4 mL使消除。铝(Ⅲ)的质量浓度在0～0.16 mg.L-1范围内与其吸光度之间呈线性关系。反应体系的吸收峰位于550 nm波长处,在此波长条件下测得其摩尔吸光率(ε)为1.5×105L.mol-1.cm-1。此方法已应用于测定黄铜、镁合金、碳酸钾及废水等试样中铝量,求得测定值的相对标准偏差(n=5)均小于2.5%。

Based on the study of optimum conditions of the reaction system,a sensitive photometric method for determination of trace amount of aluminum was proposed.Aluminum（Ⅲ） was reacted with 2 mL of 500 mg·L-1 o-HPF solution in an ammoniacal buffer medium of pH 9.5 in the presence of 4 mL of 50 g·L-1 KF solution and 2 mL of the 50 g·L-1 Tween-20 solution.Fluoride ion was used as an auxilliary complexing agent for Al（Ⅲ） and Tween-20 was used both as solubilizer and sensitizer for the chromogenic reaction.Interferences of several common co-existing metal ions [except Ti（Ⅵ）] were eliminated by adding 4 mL of 20 g·L-1 EDTA solution after the addition of KF.Linearity between values of absorbance and mass concentration of Al（Ⅲ） was found in the range of 0 to 0.16 mg·L-1.Molar absorptivity（ε） of the multi-componental reaction system found was 1.5×105L·mol-1·cm-1 at the wavelength of absorption maximum 550 nm.The proposed method was applied to the determination of aluminum in samples of brass,magnesium alloy,potassium carbonate and waste water,giving RSD′s（n=5） less than 2.5%.