Application of Derivative and Derivative-ratio Spectrophotometry in the Determination of a Binary Mixture of Naproxen and Diflunisal and a Ternary Mixture of Orphenadrine, Caffeine and Aspirin

Abstract

Two Spectrophotometric techniques for resolving a binary mixture of Naproxen (NAP) and Diflunisal (DIF) and a ternary mixture of Orphenadrine (ORPH) citrate, caffeine (CAF) and Aspirin (ASP) are presented. These techniques are based on the use of derivative and derivative-ratio spectrophotometry for the determination of these selected mixtures. For the NAP/DIF mixture, the first method involves the use of derivative spectrophotometry with the zero crossing technique where DIF was determined using 1D amplitude (Δλ=6) at 321 nm, while NAP was determined using 3D amplitude (Δλ=6) at 302 nm. The second method involves the application of the ratio spectra first derivative spectrophotometry where two points have been used for the quantitation of each compound. For the determination of DIF, NAP was used as divisor and the 1DD (Δλ=2) values at 242.9 nm were plotted against DIF concentration; while by using DIF as divisor the 1DD (Δλ=2) amplitudes at 276.6 nm were found to be proportional to NAP concentration. For the ORPH/CAF/ASP mixture, the analysis of this ternary mixture was achieved by solvent extraction of ASP then the remaining mixture of ORPH and CAF was determined by using the two spectrophotometric techniques. The first method involves the use of derivative spectrophotometry with the zero crossing technique where ORPH was determined using 1D amplitude (Δλ=6) at 241.1 nm, while CAF was determined using 1D amplitude (Δλ=6) at 257 nm. The second method includes the application of the ratio spectra first derivative spectrophotometry where two points have been used for the quantitation of each compound. For the determination of ORPH, CAF was used as divisor and the 1DD (Δλ=2) values at 229.4 nm were plotted against ORPH concentration; while by using ORPH as divisor the 1DD (Δλ=2) amplitudes at 236 nm were found to be proportional to CAF concentration. ASP was easily determined in 0.1 M HCl by direct spectrophotometric measurements (0D) of the absorbance at λ(superscript max)=301.4 nm.