Development of potentiometric flow titration for nonaqueous solvent system

建立了一种测定润滑油、食用油等油样中酸值、碱值、皂化值和溴值的流动电位滴定方法。本文的研究结果总结如下：利用乙醇pH缓冲溶液和流通式pH玻璃电极检测器，设计了一种测定油的酸碱度的流动体系。该检测器对酸和碱的灵敏度取决于样品中酸的离解常数与pH缓冲溶液中所用酸的离解常数之比。用四氯乙酸酯-四氯乙酸缓冲溶液成功地测定了润滑油的总碱度，设计了以四丁基氧化铵乙醇溶液和乙醇pH缓冲溶液为流动相，用pH玻璃电极检测器测定润滑油皂化值的流动体系。考察了流动体系中皂化反应条件对油酸乙酯和亚油酸乙酯的灵敏度。对反应线圈长50m、温度85ﾟC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，结果与常规滴定方法吻合较好。采用溴和溴组成的电位缓冲流和氧化还原电极与溴离子选择电极相结合的流动检测器设计了测定油脂中溴值的流动系统。通过考察该检测器对油酸乙酯、环己烷等不饱和化合物的灵敏度，确定了最佳检测条件。该方法已成功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