Determination of midazolam in pharmaceutical dosage forms by second-order derivative ultraviolet spectrophotometry

Abstract

A second-order derivative ultraviolet spectroscopic method for the determination of midazolam in the presence of maleic acid is described. The assays were carried out in borate buffer (pH 9.2) at a wavelength of 222 nm, which corresponds to the position of the peak of 2 D spectrum of midazolam and to the intersection point of the 2 D spectrum of maleic acid with the abscissa (zero-crossing point). These conditions were chosen as optimum on the basis of the knowledge of acid-base equilibria of midazolam and maleic acid and of investigations of the absorption and 2 D spectra of midazolam and maleic acid and their mixtures. A calibration graph was obtained in the range of midazolam concentrations of 0.25-2.5x10 -5 mol/dm 3 with a correlation coefficient of 0.99996. The method is simple and rapid, and was successfully applied to the determination of midazolam in the presence of maleic acid in laboratory mixtures and in commercial tablets containing midazolam in the maleate form.