分光光度法测定牙膏中游离氟的含量

Spectrophotometric determination of fluoride ion content in toothpaste

在碱性条件下,氟离子能使Fe3+与硫氰酸根反应生成的血红色配合物的吸光度下降,氟离子的加入量与体系吸光度的改变值成正比,且氟离子质量浓度在2.0～100.0 mg.L-1内与吸光度呈良好线性关系,线性回归方程为A495=0.002 98ρ+0.039 5,线性相关系数为0.998 3。据此建立了一种利用Fe3+与硫氰酸钾体系光度法测定氟离子的方法,并将该法用于牙膏中微量氟离子含量的测定,测定结果与氟离子选择电极法测定结果一致。

Under alkaline condition, fluoride ion can cause decline of photo absorbance of the red color coordinate compound formed by ferric ion and thiocyanate ion. Meanwhile, the change of the photo absorbance of the system is directly proportional to the amount of fluoride ion in the system, and as the concentration of the fluoride ion is ranging within 2. 0 - 100. 0 mg · L-1 , there is a good linear relationship between the photo absorbanee and the concentration of the fluoride ion. A regression equation of A495 = 0. 002 98ρ ＋ 0. 039 5 was derived with a linearity correlation coefficient of 0.998 3. Base upon the experimental result, a spectrophotometric method for determination of fluoride ion content in toothpaste was established. Adopting this method, the determination result is fully consistent with that determined by ion selective electrode method.