分光光度法测定水溶液中的有机酸含量

利用水溶液中的有机酸在高氯酸羟胺(HAP)和N,N′-二环己基碳酰亚胺(DCC)存在的条件下生成的羟肟酸,以及羟肟酸在酸性高氯酸铁溶液中显色的性质,建立了一种分光光度测定水中有机酸含量的方法。对显色剂的酸度、浓度、加入体积、HAP和DCC的浓度、加入体积以及显色反应的温度、反应时间对吸光度的影响进行了考察。结果表明,该显色反应在反应条件:0.0687mol/LHAP1.0mL、0.6mol/LDCC0.5mL、震荡均匀后室温下放置反应15min、0.02mol/L酸性高氯酸铁溶液(高氯酸浓度0.3mol/L)显色条件下具有最大的吸光度;并对正丁酸、正戊酸、苯甲酸进行了线性关系考察。结果表明,该检测方法具有仪器简单、操作方便、线性范围较宽、准确度高等优点,可用于那些不易从水溶液中萃取的有机酸的测定,也可用于液相色谱洗脱液中有机酸的测定。

Spectrophotometric Determination of Carboxylic Acids in Aqueous Solutions

Spectrophotometric determination of carboxylic acids in aqueous solutions has been developed based on the formation of hydroximic acid from carboxylic acid in the presence of hydroxylamine perchlorate(HAP) and dlcyclohexylcarbodiimide(DCC) as well as the formation of purple ferric hydroxamate from hydroximic acid in the presence of acidic ferric perchlorate solution. We have investigated the effects of acidity,concentration and addition volume of ferric perchlorate,concentration and addition volume of DCC and HAP,and reaction temperature and reaction time on the absorbance. The results illustrate that this reaction has the largest absorbance under the follow conditions: conditions of reaction: 1.0 mL of 0.068 7 mol/L HAP,0.5 mL of 0.6 mol/L DCC,after shaken,incubation of reaction mixture for 15 min at room temperature;conditions of pigmentation:0.02 mol/L acidic ferric perchlorate solution(0.3 mol/L perchloric acid). Working curves of n-butyric,n-valeric and benzoic acid have also been investigated,which indicate that this method is simple,easy to use,precise,and has a wide linear range. It can be applied to those carboxylic acids which are difficult to extract from aqueous solutions,and the application of this method for the determination of various kinds of acids in the eluate after chromatographic separation are expected to be advantageous.