Absorbance ratio Method and First Order Deriv...

Absorbance ratio Method and First Order Derivative Spectrophotometric Method for Simultaneous Estimation of Hydrochlorothiazide and Methyldopa in combined dosage form

Author Name : Madhuri Hinge, Dipti Patel

ABSTRACT

Two simple, precise and accurate methods have been developed for simultaneous estimation of Hydrochlorothiazide and Methyldopa from tablet dosage form. The first method is Absorbance ratio method (Method A) for that two wavelengths selected were 260 nm i.e. isoabsorptive point and 280 nm λ max of Methyldopa and absorbance were integrated at these selected wavelengths for both drugs. The second method is First order derivative method. The two wavelengths were selected, one wavelength at which Hydrochlorothiazide shows zero crossing point (ZCP at 242 nm) was used for estimation of Methyldopa and  another wavelength was (ZCP at 280 nm) zero crossing point of Methyldopa employed for estimation of Hydrochlorothiazide. Beer’s law was obeyed in the concentration range of 1 – 6 μg/ml for Hydrochlorothiazide and 10 – 60 μg/ml for Methyldopa respectively. The mean % Recoveries was found to be in range of 98.50 – 100.09% for Hydrochlorothiazide and 99.70 – 100.09% for Methyldopa by absorbance ratio method and 99.46 – 100.16% for Hydrochlorothiazide and 99.50 – 99.97% for Methyldopa by First order derivative method. Both methods were validated as per ICH Q2 (R1) guideline.

Keywords: Hydrochlorothiazide, Methyldopa, Absorbance ratio method, First order derivative method, Tablet.