HPLC analysis of aliphatic and aromatic dicarboxylic acid cross-linkers hydrolyzed from carbohydrate polyesters for estimation of the molar degree of substitution

Quantitative analysis of carboxylic acids in hydrophilic matrixes remains a challenge despite the introduction of derivatization reagents for carboxylic acids nearly three decades ago. Analysis of many bifunctional ester forming polymer cross-linkers are additionally complicated by the their amphiphatic character. We report a sensitive and selective HPLC method to quantify organic dicarboxylic acids resulting from the hydrolytic degradation of cross-linked carbohydrate polyesters. An important group of cross-linkers encompassing C7-C10 aromatic and non-chromophoric aliphatic diacid chlorides were investigated. Specific validation is reported for terephthalic acid, diethylmalonic acid and sebacic acid. Linear calibration curves were obtained in the 0.5-15.0 μg/ml range corresponding to a mass fraction of 0.05-1.5% diacid to polyester. The accuracy and precision in this range was 94.4-114.1 and 6.1-24.8% RSD, respectively. This method is suitable for the routine determination of the molar or mass degree of substitution in carbohydrate polyesters.