Signal processing techniques for the spectrophotometric quantitation of binary mixture of dapagliflozin and saxagliptin: A comparative study

Purpose: To investigate the advantages and drawbacks of four signal processing methods for spectrophotometric quantitation of mixtures of dapagliflozin and saxagliptin. Methods: The methods studied were numerical differentiation (ND), Savitzky-Golay filter (SG), discrete Fourier transform (DFT) and continuous wavelet transform (CWT). The resolution powers of the methods were compared via quantitative determination of dapagliflozin (DAP) and saxagliptin (SAX) in laboratory prepared mixtures. Furthermore, a new approach for validating robustness in spectrophotometric methods was developed, and the methods were compared using their robustness. Results: Continuous wavelet transform (CWT) produced the best results regarding the analysis of the two drugs in different ratios. It also showed a lower limit of quantification (LOQ), when compared to each of the other methods. When the four methods were used for quantitation of pharmaceutical drug formulations, and subjected to validation in line with ICH regulations, they were found to be satisfactorily specific, accurate, precise and robust. Conclusion: These results show that CWT technique is superior to the other three methods for analysis of drug mixtures with regard to sensitivity and resolving power. Thus, CWT can be used in the routine spectrophotometric analysis of pharmaceuticals in quality control laboratories.