Extractive spectrophotometric determination of atorvastatin in bulk and pharmaceutical formulations

New spectrophotometric procedures have been established for the assay of atorvastatin either in bulk form or in pharmaceutical formulations. The procedures are based on the reaction between the examined drug and bromocresol green, alizarin red, or bromophenol blue producing an ion-pair complexes which can be measured at the optimum wavelengths. The optimization of the reaction conditions is investigated. Beer's law is obeyed in the concentration ranges 5.0-53.0 mug mL(-1), 7.1-55.8 mug mL(-1), or 7.5-56.0 mug mL(-1) with bromocresol green, alizarin red, or bromophenol blue, respectively. The composition of the ion-pairs was found 1:1 by Job's method. The specific absorptivitics, molar absorptivities, Sandell sensitivities, standard deviations, and percent recoveries are evaluated. On the other hands, atorvastatin was determined by measurement of its first derivative signals at 217.8 nm, respectively. Calibration graph was established for 4.2-69.0 mug mL(-1) of atorvastatin for first derivative spectrophotometry. Application of the suggested methods to pharmaceutical formulations is presented and compared with the first derivative spectrophotometric method. No interference was observed from common pharmaceutical adjuvants.