Simultaneous determination of a quaternary mixture of oxomemazine, sodium benzoate, guaifenesin and paracetamol by chromatographic methods

The aim of the present work was to develop simple, accurate, sensitive and selective methods for the simultaneous determination of oxomemazine (Ox), sodium benzoate (SB), guaifenesin (Gu), andparacetamol (Par). Two methods were described and validated for the simultaneous determination of the four drugs in syrup and suppositories. The first method was a reversed phase HPLC and UVdetection at 220 nm. The assay was performed using C 18 column and an isocratic elution using acetonitrile – methanol – 35 mM KH2PO4 (20: 5: 75; by volume, pH was adjusted to 2.9 ± 0.1) as the mobile phase. The flow rate was 1.5 mL/min and separation was achieved in less than 15 min. The second method was a TLC- spectrodensitometric method, used to separate, identify and quantify the four drugs when present in combination. The drugs were applied on silica gel plates and development was made using methylene chloride- methanol- acetic acid- 33% ammonia (89: 8.4: 2: 0.6, by volume) as a mobile phase. The bands of the four drugs were quantified by scanning spectrodensitometricaly at 270 nm. The suggested chromatographic methods were validated and applied successfully to the analysis of the syrup and suppositories.