Spectrophotometric methods for the determination of omeprazole in bulk form and pharmaceutical formulations

Four simple and sensitive methods for the assay of omeprazole (OMZ) were developed. These methods are based on the formation of colored species by treating OMZ with 3-methyl-2-benzothiazolinone hydrazone (MBTH) following oxidation with ferric chloride (method A) or m-aminophenol following oxidation with chloramine-T (CAT) (method B) or Folin-Ciocalteau reagent (FC) (method D), or by oxidizing OMZ with excess N-bromosuccinimide (NBS) and determining the consumed NBS with a decrease in color intensity of Celestine blue (CB) (method C). All variables have been optimized. Regression analysis of Beer's plots showed good correlation in the concentration range of 1.0-10, 2.0-32, 0.4-2.4 and 0.8-10 mug ml(-1) for methods A, B, C and D, respectively. No interference was observed for formulation additives and the validity of each method was tested by analysing capsules containing OMZ. Recoveries were 98.7-100.1%.