Ratio subtraction and isosbestic point methods are two innovative spectrophotometric methods for determining the concentrations of metronidazole (I) and diloxanide furoate (II) in a mixture. Metronidazole was determined by direct spectrophotometric method at kmax nm in the presence of diloxanide furoate in the range of 4–24 lg ml1 with a mean recovery percentage of ± . Two spectrophotometric methods were developed for the spectral resolution of diloxanide furoate when present in mixture with metronidazole without preliminary separation. The first method depends on measuring the absorbance at the isosbestic point at nm in the range of 5–30 lg ml1 with a mean recovery percentage of ± for diloxanide furoate. The second method is the ratio subtraction spectroscopic method for spectral isolation of diloxanide furoate present in the mixture which can be measured at nm in the range of 5–30 lg ml1 with a mean recovery percentage of ± for diloxanide furoate determination. The suggested procedures were validated using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical preparations. The methods retained their accuracy and precision when the standard addition technique was applied. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the reported method. | Spectrophotometric methods for the simultaneous determination of binary mixture of metronidazole and diloxanide furoate without prior separation
