Background: The ability of the normalized spectra when used as a divisor and in combination with isosbestic point to resolve complex binary or ternary mixtures, Candesartan and Hydrochlorthiazide binary mixture was taken as a model.
Introduction: A green simple smart and accurate method using ethanol as a solvent namely simultaneous derivative ratio (SIDD) was applied to prove the power of normalized spectra and isosbestic point as spectrophotometric resolving tools.
Methods: In the proposed SIDD method, the zero order spectra of drugs were simply manipulated using the normalized spectra of CAN as divisor to obtain the ratio and first derivative spectra in two successive steps. Firstly, the total amplitude at isosbestic point 255.4 nm of the ratio spectra of the mixture was measured representing the total actual concentration of both drugs in the mixture. Then, the first derivative of the ratio spectra was obtained to determine Hydrochlorothiazide concentration at 233 nm. While the concentration of Candesartan was determined subsequently by subtracting the Hydrochlorothiazide concentration calculated after derivatization from the total concentration of both drugs obtained at the ratio spectra before the derivatization step.
Results: The SIDD was successfully applied for simultaneous determination of both drugs in their pure form or in their binary mixture either in synthetic prepared mixtures or in combined dosage form the adopted method was validated according to the ICH guidelines and the results were found to be within the acceptable limits.
Conclusion: The adopted method highlighted the important role of normalized spectrum when used as a divisor in addition to the importance of isosbestic point to resolve severely overlapped spectra. All the measurements were carried using ethanol which is considered one of the greenest solvents making the method an environmentally friendly one. the adopted method was validated according to the ICH guidelines and the results were found to be within the acceptable limits.
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