偶合化学发光法测定食用油脂碘值的研究

Determination of iodine value in edible oils by coupling chemiluminescence method

为建立一种测定食用油脂碘值的化学发光新方法,选用椰子油、棕榈油和无水奶油等为材料,用含一氯化碘的乙酸溶液与油脂中的不饱和脂肪酸发生加成反应,余剩的一氯化碘与碘化钾作用生成的单质碘在碱性水溶液中氧化鲁米诺(Luminol)产生波长为425 nm的可见光,利用Luminol-I2偶合化学发光体系,对样品进行了测定。通过YN-FGI化学发光仪记录其发光面积。结果表明,碘(I3-)浓度在1.30×10-5～2.60×10-4mol/L范围内与相对发光面积呈现良好的线性关系,线性方程为Y=7.004×104X,相关系数r为0.997 1,碘(I3-)液检出限为6.0×10-6mol/L。对1.30×10-5mol/L的碘(I3-)液平行测定11次,其RSD为3.0%。样品与国标法对照测定无显著性差异,用于食用油脂碘值的测定,结果令人满意。

A new method for determination of iodine value in edible oils was explored by chemiluminescence. Choosing coconut oil, palm oil and cream as samples, acetic acid containing iodine chloride was used to react with unsaturate fatty acid in oil by addition reaction. Iodine generated by the reaction of the surplus of iodine chloride with potassium iodide oxidized Luminol in alkaline solution to emit 425 nm wave visible light. Luminol- I2 coupling chemiluminescence was used to determine samples. The results showed that the linear range of I3^- was 1.30×10^-5-2.60×10^-4 mol/L. The linear equation was Y=7.004×10^4X （r=0.997 1）. The detection limit of I3^- was 6.0×10^-6mol/L, the relative standard deviation（RSD） was 3.0% for I3^- concentration 1.30×10^-5mol/L（n=11）. The method was successfully used for the determination of iodine value in edible oils with satisfactory results.