One sample of phenobarbital was eluted quantitatively from the adsorbent with diethyl ether containing 2 z ethanol as a preservative. Prior experimental data showed that diphenylhydantoin was not eluted from the adsorbent with diethyl ether. Preparations containing sodium salts of phenobarbital and/or diphenylhydantoin would probably have to undergo acidification and extraction before column separation.
Mephobarbital and diphenylhydantoin recoveries were determined individually before synthetic mixtures were prepared. Recoveries were 98-99Z for 80-115 mg. of mephobarbital and 99-101 % for 40-100 mg. of diphenylhydantoin. Synthetic mixtures containing 90-150 mg. of mephobarbital and 40-100 mg. of diphenylhydantoin were then separated. Recoveries were 98 f 0.5% for mephobarbital and 102 f 1 % for diphenylhydantoin. A small amount of mephobarbital tailing enhanced the background absorbance of diphenylhydantoin, resulting in slightly high diphenylhydantoin recoveries and low mephobarbital recoveries. This tailing could not be reduced experimentally, but its effect was minimized by subtracting the background absorbance. When recoveries were calculated with the corrected absorbances, recovery values for mephobarbital and diphenylhydantoin approached closest to 100%.