Quantification of 1,3-dimethylol-5,5-dimethylhydantoin and its decomposition products in cosmetics by high-performance liquid chromatography

We developed a method to simultaneously and quantitatively measure four compounds commonly found in commercial cosmetics: 1,3-dimethylol-5,5-dimethylhydantoin (DMDMH) and its decomposition products 1-hydroxymethyl-5,5-dimethylhydantoin (1-MDMH), 3-hydroxymethyl-5,5-dimethylhydantoin (3-MDMH), and 5,5-dimethylhydantoin (DMH). In addition, we succeeded in synthesizing 3-MDMH selectively from DMDMH. Our new analytical method involves the use of an HPLC system and an octadecylsilanized silica column. HPLC calibration curves for DMDMH, 1-MDMH, 3-MDMH, and DMH were linear over the wide concentration ranges. In cosmetics whose pH is basic, the recovery of 3-MDMH and DMH was substantially higher than 100%, whereas that of DMDMH and 1-MDMH was considerably lower than 100%, however, the average recovery of the four compounds was in the range of 85-105%. It was suggested that the latter tend to decompose to the former. We confirmed that our HPLC separation method is suitable for the analysis of dimethyhydantoins without the progress of decomposition and should be useful for rapid analysis of these compounds in cosmetics.