SPECTROPHOTOMETRIC DETERMINATION OF SOME PHARMACEUTICAL COMPOUNDS USING 2,2-DIPHENYL-1-PICRYLHYDRAZYL

A simple, rapid and sensitive spectrophotometric procedure for the assay of some drugs has been developed. The method is based on the reaction of the studied drugs with 2,2-diphenyl-1-picrylhydrazyl (DPPH). The latter is employed to abstract a hydrogen atom from the drugs thereby promoting a process of radical coupling. This results in a reduction of the violet color of DPPH with the formation of the yellow colored 2,2-diphenyl-1-picrylhydrazine (DPPH₂). The decrease in the intensity of the violet color is used to measure the concentration of the drugs. All measurements are made at λ= 520 nm on methanolic solutions of the reagent and drugs. Beer's law is obeyed in the ranges of 5-30 µg/ml (for aceclofenac, diclofenac sodium and thiaprofenic acid), 2-15 µg/ml (for tenoxicam, furosemide and lansoprazole) and 2-12 µg/ml (for benoxinate hydrochloride and ritodrine). The validity of the method was tested by carrying out standard addition procedure analyzing the studied drugs in pure form as well as in their pharmaceutical preparations without interference from common additives. Results of the proposed methods are in good agreement with those of the official or reported methods.