紫外分光光度法测定饮料中山梨酸钾的含量

Determination of potassium sorbate in drinks by UV-spectrophotometric

采用紫外分光光度法测定山梨酸钾。在253 nm处有最大吸收峰,而且在较大范围内具有良好的线性关系,但饮料中含有的维生素C在紫外区也有吸收,直接测定会有很大误差,将山梨酸钾转化成山梨酸,用氯仿萃取,再用碳酸氢钠溶液反萃取,而后用紫外分光光度法测定。

Potassium sorbate is determined by UV-spectrophotometric, which has maxmum observition λ at 253 nm, and its excellent linear relationship at relative wide wavelengths makes the UV-spectrophotometer feasible. But vitamin C also has evident absorbance at UV band, which makes that the direct determination inevitably brings unsatisfactory error. So the conversion of potassium sorbate into sorbic acid, which is followed by extraction with chloroform and back-extraction with sodium bicarbonate and makes the UV-spectrophotometer effective.