非线性优化迭代-紫外分光光度法同时测定苯甲酸钠和山梨酸钾

提出一种用连续波长的紫外光谱吸光度数据对两组分防腐剂（苯甲酸钠、山梨酸钾）混合物体系的定量分析方法。该方法利用连续波长信息将摩尔吸光系数和待测浓度同时作为自变量，建立非线性优化模型，对于组分浓度差较小的混合物体系经一次优化分析计算可得待测浓度；混合物中浓度差较大的体系经四次左右优化迭代，逐步降低误差得分析结果，相对误差可控制在1．52％之内。分析结果表明该法稳定、准确、简便快速、实用灵活，可对食品防腐剂进行定量测定。

Simultaneous determination of sodium benzoate and potassium sorbate by ultraviolet spectrophotometry with nonlinear iterative optimization

The simultaneous multi-component quantitative determination of eatable preservatives(sodium benzoate,potassium sorbate) was proposed using continuous wavelength ultraviolet spectrophotometry without any chemical separation procedure.The method uses the absorptivity coefficient and component concentration of solutions as independent variables at the same time and sets up a constrained optimization model to solve it by generalized reduced gradient.The concentration awaiting test can be obtained after one optimization calculation to the mixed solution in which the concentration of every component is close to each other.But to some solutions in which component concentration is not close to each other,iterative optimization is necessary.The last results obtained are satisfactory with a good accuracy and precision only after about 4 times iterations,and the relative error can be controlled in 1.52%.So this method can be used to determine quantitatively eatable preservatives.