LAUSR

An aqueous normal-phase high-performance liquid chromatography method was developed to separate cis/trans isomers of 4,5-dihydroxyimidazolidine-2-thione and 4,5-dimethoxyimidazolidine-2-thione on a Luna HILIC 200 Å column containing silica surface covered with cross-linked diol with an eluent acetonitrile/water in the ratio of 95:5 v/v. Changing of the analysis parameters leads to selectivity of cross-linked diol towards analyte with a predominance of adsorption mechanism between the phase and compounds. The separation in reversed-phase and normal-phase modes are unsuccessful. Chromatographic peaks of the cis/trans isomers are identified by the HR-LC–MS and the spectral ratios. The results of the determination of the isomer ratio for 4,5-dihydroxyimidazolidine-2-thione by the HPLC are consistent with the 1H NMR data. The existence of the previously undescribed cis-4,5-dimethoxyimidazolidine-2-thione is confirmed by the HR-HPLC–MS. This method allows providing simultaneous rapid separation and determination of the ratio of isomers in the samples of 4,5-dihydroxyimidazolidine-2-thione and 4,5-dimethoxyimidazolidine-2-thione.