An approach to quantitative two-component analysis of a mixture containing hydrochlorothiazide and spironolactone in tablets by one-dimensional continuous Daubechies and biorthogonal wavelet analysis of UV-spectra

In this study a new method of quantitative two-component analysis of a mixture of hydrochlorothiazide (HCT) and spironolactone (SP) in the presence of strongly overlapping signals was achieved by using one-dimensional continuous wavelet analysis. This new method was built on the simultaneous use of both continuous wavelet transform and the zero crossing technique for the quantitative resolution of this binary mixture. A series of solutions, in the concentration range of 2-22 mg/ml for both compounds, in methanol and 0.2 M sodium acetate buffer, pH = 5 (20:80), were considered. The absorption spectra of the standard solutions were recorded in the wavelength range of 215-330 nm. To apply our methods we selected 400 points from the absorption spectra and we subjected the corresponding signal to Daubechies2 (DAUB2) and Biorthogonal1.5 (BIOR1.5) one-dimensional wavelet transform. In the transformed signals, the amplitude of HCT was measured at the position of a zero crossing point of SP and vice versa. Thus simple linear regression analysis can be applied to establish calibrations for both components. These calibrations were validated with synthetic mixtures of HCT and SP. MATLAB 6.5 software was used for one-dimensional wavelet analysis, and the basic concepts about wavelet method are briefly explained. The method developed in this paper is rapid, easy to apply, inexpensive and it is suitable for analysis of the overlapping signals of compounds in their mixtures without any chemical pre-treatment.