火焰原子吸收法间接测定混凝土外加剂中的微量Cl^-

Determination of Chloride Ion in Additives of Concrete by Flame Atomic Absorption Spectrometry

火焰原子吸收法以其灵敏度高、选择性好等优点而广泛应用于各种基体中微量金属元素的测定 ,而不用于直接测定Cl- 。本文提出了采用火焰原子吸收法间接测定混凝土外加剂中微量Cl- 的方法 ,在待测液中加入过量的Ag+ 标液 ,通过测定与Cl- 定量反应后剩余的Ag+ 量从而换算出Cl- 的含量 ,本法进行了测定最佳酸度试验、精密度试验、在样品中加入Cl- 标准溶液回收试验 ,回收率为 96 %～ 10 4 %。经过实际样品测定 ,证明该方法具有样品预处理手续简单、测定周期短、干扰小等优点 ,最适合于测定基体较为复杂的混凝土外加剂中的微量Cl- 。称取样品 0 0 5～ 2g ,溶解后 ,用硝酸调节酸度 ,加入与之对应的Ag+ 标准溶液 ,放置 2h过滤后即可测定 ,所用仪器为澳大利亚GBC90 2型原子吸收光谱仪。

Flame atomic absorption spectrometry due to its high sensitivity and selectivity has been widely used for the determination of micro levels of metal elements in various materials. But this method can not be used for the determination of Cl- directly. In this paper the determination of Cl- in additives of concrete by flame atomic absorption spectrometry was studied. Adding superfluous standard solution of Ag+ to the sample solution, the results were obtained by determining the remanent content of Ag+ having reacted with Cl- quantitatively. The acidity of the sample solution and the precision were studied. The standard rate of recovery obtained was in the range of 96% -104%. By the determination of actual samples it was proved that the method features simple sample preparation, fast determination, and little interference, especially for those samples which contain micro levels of Cl-. The procedure is as follows: weigh 0.05-2 g of sample, dissolve it in water and adjust the acidity with nitric acid, add proper standard solution of Ag+, and after 2 h, measure the remanent Ag* content by atomic absorption spectrometry. A GBC902 atomic absorption spectrometry was employed.