高效液相色谱法测定桐油酸及其衍生物的离解常数

Determination of the Dissociation Constants of Eleostearic Acid and its Derivative by HPLC

采用高效液相色谱法（HPLC）测定了桐油酸、3-正丁基-6-（1-癸烯酸甲酯基）-4-环己烯二酸（C23二酸甲酯）和3-正丁基-6-（1-癸烯酸基）-4-环己烯二酸（C22三元羧酸）的离解常数。用HPLC测定样品在不同pH（2．00～12．00）下的容量因子，通过最小二乘法计算出相应的离解常数。通过不同流动相比例下的离解常数计算出样品在纯水中的离解常数。实验得到的结果与用ACD／Lab软件计算得到的结果相近。桐油酸的pKa为4．79；C23二酸甲酯的pKa1为3．81，pKa2为5．78；C22三元羧酸的pKa1为3．68，pKa2为4．77，pKd为5．73。

The dissociation constants of eleostearic acid, 3-n-butyl-6-（ 1-decyl otefinic acid base） 4-cyclohexene diacid （ C23 diacid methylester） and 3-n-butyl-6-（ 1-decyl olefinic acid methyl ester） 4-cyclohexene diacid （C22 tricarboxylic acid） were determined by High Performance Liquid Chromatography （HPLC）. Observed retention factors were determined using mobile phases with different percentages of organic modifier in the pH range from 2. 00 to 12.00. A two- stage least squares fitting procedure for fitting a general equation to the observed retention factors was used to calculate the dissociation constants at each percentage of organic modifier. The obtained dissociation constants were extrapolated to give pK, values in 100% aqueous solutions. The obtained pK, values were of an extrapolated to be calculated by ACD procedure. The eleostearic acid has a pKa of 4.79 and the C23 diacid methyl- ester has a pK,l of 3.81 ,a pK.2 of 5.78. The C22 tricarboxyl- ic acid has a pK,l of 3.68, a pK,2 of 4. 77,a pK,3 of 5.73.