Utility of p-Chloranilic Acid and 2,3-Dichloro-5,6-dicyano-p-benzoquinone for the Spectrophotometric Determination of Rizatriptan Benzoate

Abstract

Rizatriptan is a new selective 5-HT1B/1D agonist which is used in the treatment of migraine headaches. Two simple, rapid, accurate, and economical spectrophotometric methods are described for the determination of rizatriptan benzoate (RTB) in its pure form and pharmaceutical preparations. These methods are based on the charge-transfer complexation reaction between rizatriptan benzoate as n-electron donor and p-chloranilic acid (p-CA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as π-acceptor to form highly colored chromogens. The chromogens formed by the reaction between RTB and p-CA peaked at 530 nm (method A) and that formed by the reaction between RTB and DDQ peaked at 590 nm (method B). Under the optimum conditions Beer’s law is obeyed in the concentration range of 14–245 μg mL−1 for method A and 4–70 μg mL−1 for method B. The coefficient of correlation was found to be 0.9999 for both methods. The molar absorptivity, Sandell sensitivity, limits of detection, and quantification are also reported. The stoichiometric relationship determined by Job’s continuous method was found to be 1 : 1 (drug : reagent) for both methods. Both methods were applied to determination of RTB in the pharmaceutical formulations. Results of the analysis were validated statistically.