Nina Alizadeh - Department of Chemistry, University of Guilan, Namjoo Street, Rasht, P.B. ۴۱۳۳۵-۱۹۱۴, Iran
Mohammad Mahjoub

A new sensitive extractive spectrophotometric method for the assay of diazepam in pure form and pharmaceutical formulations with methyl orange wasdeveloped. The proposed method is based on the formation of an ion-paired colored complex between diazepam and methyl orange with light yellow color,was extracted in to chlorophorm at pH 4.2. The maximum absorbance of the ion-pair determined at 411 nm. The molar absorptivity was 5.3×103 l mol-1cm-1 and sandell's sensitivity was 67.6×10-3 μg cm-2. Optimum reaction conditions and other important analytical parameters for the reaction system were investigated.The system obey beer's law over the concentration rang 4 to 50 μg ml-1. The effectiverange of concentration for accurate determination as ascertained from Ringbom's plot obtained 16.67-50 μg ml-1. The ratio of ion-pair (drug:ligand) was 1:1 asestablished by job's method. The proposed method has been applied successfully to the analysis of drugs dosage forms and no interference was observed fromcommon excipients present in pharmaceutical formulations. The results obtained by the proposed method were statistically compared by means of student t-test and by the variance ratio, F-test with HPLC method and here shown to be an excellentagreement with official method. The proposedmethod is sensitive, rapid and economic.