Determination of phenytoin, phenobarbitone and methyl phenobarbitone in combination

This work is concerned with the determination of a mixture of phenytoin, phenobarbitone and methylphenobarbitone by two different techniques. The first one depends on the simultaneous quantitative densitometric evaluation of thin layer chromatograms of the three drugs. The second is the application of quantitative H-1-NMR spectrometry for the simultaneous determination of phenobarbitone and methylphenobarbitone in the presence of phenytoin, while phenytoin was determined in this mixture by modifying the benzophenone spectrophotometric procedures.((1-4)) The proposed procedures were proved using laboratory prepared mixtures of the three drugs and were successfully applied for their analysis in tablet form. The validity of the proposed procedures was further assessed by applying the standard addition technique.