Spectrophotometric and Differential Pulse Polarographic Methods of Analysis for Ketotifen Hydrogen Fumarate

Abstract

Spectrophotometric and differential pulse polarographic methods have been proposed for the assay of ketotifen hydrogen fumarate in authentic powder and in capsule dosage forms (Zaditen^(R)), using acetate buffer of pH 5.0 as a solvent as well as a supporting electrolyte. Ketotifen hydrogen fumarate exhibits relatively strong absorption in the ultraviolet region with maximum absorption at 300 nm; the molar absorptivity, $eP_max, and specific absorbance, A (1 per cent, 1 cm), being 1.38 × ⁴ L mole⁻¹ cm⁻¹ and 325 respectively. Beer's Law was verified; the absorbance, (A_max), was found to be linearly related to concentration, C, over the range 2 to 30 ug ml⁻¹. The mean percentages of recovery for ketotifen hydrogen fumarate powder and in capsule form obtained spectrophotometrically were 100.85 $pM 0.56 and 99.75 $pM 0.85 respectively.

Differential pulse polarograms were recorded at room temperature under constant pulse amplitude of 50 mV superimposed on a linearly increasing DC-voltage ramp. The peak current, i, of the polarogram was measured at the peak potential of -1.06 V on the dropping mercury electrode, (dme), versus Ag/AgCl reference electrode. A linear relationship between the peak current and concentration, C, was observed over the range 5 to 70 ugm⁻¹ The mean percentages of recovery obtained polarographi-cally for ketotifen hydrogen fumarate in bulk and in capsule form were 99.33 $pM 1.12 and 101.15 $pM 0.70 respectively.

The purity of authentic ketotifen hydrogen fumarate was checked by nonaqueous potentiometric titration using 0.1 N - perchloric acid.