Fast Spectrophotometric Determination of Iodine Value in Biodiesel and Vegetable Oils
Fast Spectrophotometric Determination of Iodine Value in Biodiesel and Vegetable Oils
复制标题
快速分光光度法测定生物柴油和植物油中的碘值
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
F. R. Rocha
中科院分区：
文献类型：
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作者：
Samara Soares;F. R. Rocha
碘值是评价生物柴油和植物油氧化稳定性的重要质量参数，但官方方法费时费力，需要大量的试剂和溶剂。本工作描述了一种新的测定碘值的方法，该方法基于样品中不饱和化合物的卤化导致三碘化水溶液变色。碘被提取到有机相中，并与样品中不饱和化合物的数量成比例地消耗。因此，用分光光度法定量的水相中碘的剩余部分与不饱和化合物的浓度成反比。对于生物柴油样品，其线性范围为10~106g/100g，变异系数为5.0%(n=8)，检出限为2.5g/100g。植物油的相应值分别为20~140g/100g、3.0%(n=10)和7g/100g。该方法每次测定仅消耗1.2mL样品、365mgI2和42毫克KI，产生约2.4mL废物。在95%的置信度水平下，结果与官方方法的结果一致。
Iodine value is an important quality parameter for evaluation of the oxidative stability of biodiesel and vegetable oils, but the official methods are time-consuming and demand large amounts of reagents and solvents. The present work describes a novel procedure for determination of iodine value based on the discoloration of a triiodide aqueous solution due to halogenation of the unsaturated compounds in the samples. Iodine is extracted to the organic phase and consumed proportionally to the amount of unsaturated compounds in the samples. Thus, the remaining fraction of I3 quantified by spectrophotometry in the aqueous phase is inversely proportional to the concentration of unsaturated compounds. For biodiesel samples, responses were linear from 10 to 106 g I2 per 100 g, with coefficient of variation and limit of detection estimated at 5.0% (n = 8) and 2.5 g I2 per 100 g, respectively. The corresponding values for vegetable oils were 20 to 140 g I2 per 100 g, 3.0% (n = 10), and 7 g I2 per 100 g, respectively. The procedure consumed only 1.2 mL of sample, 365 μg of I2, and 42 mg of KI with ca. 2.4 mL of waste generated per determination. The results agreed with those obtained by the official methods at the 95% confidence level.