摘要
研究了用盐酸-异丙醇直接滴定法和两相滴定法分别测定烷基羧基甜菜碱样品中游离叔胺含量和活性物含量。结果表明,用盐酸-异丙醇直接滴定法测定游离叔胺,对双十二烷基甲基羧基甜菜碱样品滴定终点为浅黄色,与用标准盐酸溶液滴定单纯的叔胺产品相同,但对十六烷基二甲基羧基甜菜碱样品,滴定终点为蓝绿色而非黄色,以黄色为终点将高估叔胺含量。与滴定单纯的叔胺产品相比,大量甜菜碱的存在使滴定过程中pH的突跃消失,体系pH随滴定体积的增加缓慢下降,但滴定单位质量叔胺所消耗的盐酸-异丙醇的体积不变。由于指示剂颜色亦呈现缓慢的变化,仍可以根据指示剂颜色变化来确定终点。终点颜色不随叔胺含量而变化,但可能因甜菜碱的分子结构而异。在酸性条件下,叔胺与甜菜碱都显示阳离子性质,可以用两相滴定法测出两者总量。于是在用盐酸-异丙醇直接滴定法独立确定样品中游离叔胺的情况下,通过两相滴定即可测出样品中甜菜碱活性物含量。
Methods for determination of contents of free tertiary amine and active matter in alkylearboxybetaine （ACB） products by direct titration with standard HCl -isopropanol solution and two- phase titration respectively were studied. Results showed that for product of ACB with double long alkyl chains, such as didodecylmethylcarboxybetaine,the free tertiary amine in the ACB product can be accurately measured by titrating sample solution with HCl - isopropanol solution and light - yellow color can be taken as the end - point,which is similar to the titration of single tertiary amine product. However, for product of ACB with single long alkyl chain, such as hexadecyldimethylcarboxybetaine, the titration end -point of the tertiary amine should be taken as blue - green, whereas the light - yellow end - point will result in an over - estimation. Compared with the titration of single tertiary amine product, the presence of large amount of betaine will cause the disappearance of the pH jump point and the pH of the systems decreases slowly with increase of the volume of HCl- isopropanol solution, while the volume of HCl - isopropanol solution required for neutralizing unit weight of tertiary amine is a constant. Since the color of indicator also changes gradually, it is still possible to determine the end - point based on the color of the solution,which does not change with the content of tertiary in the product, but may depend on the molecular structure of the betaines. In acidic condition, both the tertiary amine and hetaine molecules display similar property as a cationic surfactant in the two - phase titration. Thus, the total content of free tertiary amine and betaine can be obtained by the two -phase titration method, and the content of betaine can be calculated once the content of the tertiary amine is determined independently by direct titration with HCl -isopropanol solution.
出处
《日用化学工业》
CAS
CSCD
北大核心
2011年第1期68-72,共5页
China Surfactant Detergent & Cosmetics
关键词
甜菜碱
叔胺
盐酸-异丙醇
两相滴定
betaine
tertiary amine
HCl - isopropanol
two - phase titration
