Formation constants of gold complexes containing hydantoin derivatives such as l-methylhydantoin (MH), 5,5-dimethylhydantoin (DMH), 1,5,5-trimethylhydantoin (TMH), and 5,5-dimethyloxazolidine-2,4-dione (DMOD) were evaluated by analyzing the amount of chloride ions which were emilinated upon coordination of the hydantoin derivatives to a tetrachloroaurate ion. Electrochemical chloride ion sensor proved to be a convenient probe to determine the concentration of the chloride ion. The formation constants decreased with the ligands in the order of TMH>DMH>DMOD>MH, which were consistent with the order of stability expected from polarization curve measurements.
