Conclusion
In this study, we proposed a method for determining the CDA content in a mixture of dimer acids using a 1H NMR analysis. The CDA content was estimated by the standard curve of mesitylene with the CDA to IS signal area ratio and compared to an equation proposed previously [20]. The reliability of the proposed method was demonstrated by quantifying mesitylene, an easy accessible cyclic standard material. Based on the verification results using mesitylene, the accuracy of our method and the equation were 98% and 95%, respectively. The accuracy is defined as the mass difference ratio between the input mass and the estimated mass of mesitylene. The key advantage of this method is that it does not require a high purity analyte standard but an easily accessible pseudo standard and IS for the content determination. Moreover, a quantitative NMR analysis provides quantification of CDA on as low as a micro-gram scale. The proposed method can be applied in various fields that require quantification of specific cyclic compounds in mixtures of pharmaceuticals or processed food.