Development of potentiometric flow titration for nonaqueous solvent system

本课题旨在建立一种测定润滑油、食用油等油样酸值、碱度、皂化值和溴值的电位流滴定法。以下是本项目的成果总结。采用乙醇pH缓冲液和流动式pH玻璃电极检测器，设计了一套测定油脂酸值和碱度的流动系统。发现检测器对酸和碱的灵敏度取决于样品中酸的解离常数与用于pH缓冲溶液的酸的解离常数的比值。用四氯乙酸-四氯乙酸缓冲液成功地测定了润滑油的总碱度。采用四丁基氧化铵乙醇溶液和乙醇pH缓冲液，采用pH玻璃电极检测器，设计了测定油脂皂化值的流动系统。考察了流动体系皂化反应条件对油酸乙酯和亚油酸乙酯的敏感性。对反应线圈长度为50 m，温度为85℃的流动体系进行了优化，并将该方法应用于黄油样品皂化值的测定，结果与常规滴定法吻合较好。采用由溴和溴组成的电位缓冲液流和由氧化还原电极和溴离子选择电极组成的流动检测器，设计了一种测定石油中溴值的流动系统。通过对油酸乙酯、环己烷等不饱和化合物的灵敏度测试，确定了最佳检测条件。该方法成功地应用于润滑油中溴值的测定

The purpose of this project is to develop a potentiometric flow titration method for determination of acid value, alkalinity, saponification value and bromine value of oil sample such as lubricating oil and food oil. Followings are the summary of results of this proiect.A flow system for determination of acid value and alkalinity of oil was designed by using an ethanolic pH buffer solution and a flow-through type pH glass electrode detector. The sensitivity of the detector to acids and bases was found to depend on the ratio of dissociation constants of acid in the sample to that of acid used for the pH buffer solution. Total alkalinity of lubricating oil was successfully determined by the developed method by using the tetrachloroacetate-tetrachloro acetic acid buffer.A flow system for determination of saponification value of oil was designed by using both streams of an ethanol solution of tetrabutylammonium oxide and an ethanolic pH buffer solution and the pH glass electrode detector. The reaction condition of saponification in the flow system was examined with respect to sensitivity for oleic acid ethylester and linoleic acid ethylester. The flow system with a reaction coil of 50 m-long and the temperature of 85ﾟC was optimized The developed method was applied to determination of saponification value of a butter sample and the result was found to be good agreement with that of a conventional titration method.A flow system for determination of bromine value of oil was designed by using a stream of potential buffer consisted of bromide and bromine and a flow-through detector combined a redox electrode with a bromide ion-selective electeode. An optimized condition was established by examining the sensitivity of the detector to unsaturated compounds such as oleic acid ethylester, cyclohexane. The developed method was successfully applied to determination of bromine value of lubricating oil