铬天青S光度法测定塑料薄膜镀铝厚度

Determination of aluminizing thickness on plastic film by chrome azurol S spectrophotometry

采用铬天青S光度法测定镀铝薄膜中铝的含量,然后由铝的密度和单位薄膜面积的镀铝量计算出膜镀铝的厚度。研究了铝与铬天青S(CAS)的显色反应,结果表明,在pH 5.5的缓冲溶液中,铝离子与铬天青S(CAS)生成络合物,最大吸收波长为610nm,表观摩尔吸光系数ε=3.89×104 L·mol-1·cm-1。在优化条件下,铝的质量浓度在0.004～0.20μg/mL与吸光度呈良好的线性关系,检测限为0.004μg/mL。对塑料薄膜镀铝样品进行加标回收试验,测得铝的加标回收率在97%～102%之间。方法测定了塑料薄膜镀铝样品的镀铝厚度,测定结果的相对标准偏差(n=6)小于3%。

The content of aluminum in aluminizing plastic film was determined by chrome azurol S spectrophotometry. Then, the thickness of aluminizing layer was calculated according to the density of aluminum and the mass of aluminizing layer on unit area of plastic film. The coloring reaction be- tween aluminum and chrome azurol S （CAS） was studied, the results showed that aluminum could re- act with CAS to form a complex in buffer solution at pH 5.5. The maximum absorption wavelength of the complex was 610 nm. The apparent molar absorptivity was ε=3.89 ×104 L·mo1^-1·cm^-1. Un- der the optimal conditions, the mass concentration of aluminum in range of 0. 004-0.20 μg/mL was linear to the absorbance. The detection limit for aluminum was 0. 004μg/mL. The recovery test of a- luminizing plastic film sample was performed. The recovery rates of aluminum were between 97 % and 102 %. The proposed method was applied to the determination of aluminizing thickness on plastic film, with relative standard deviation （RSD, n=6） less than 3 %