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Original Article

Subject Areas



Hydrochlorothiazide; Methyldopa; Aldoril tablets; derivative spectrophotometry; PLS


Two new analytical methods are described asconvenient and useful alternatives for simultaneous determination ofhydrochlorothiazide (HCTZ) and methyldopa (MD) in their combinations. The firstmethod depends on the first order derivative spectrophotometry by measuring theamplitudes at zero-crossing wavelengths of 286 and 270 nm for HCTZ and MD,respectively. In the second method, partial least squares (PLS) analysis of theultraviolet absorption spectra of the samples in the 240-340 nm region wasapplied. The methods were calibrated between 3.5 and 35.7 mg mL-1 for HCTZ and between 2.5 and 25.3 mg mL-1 for MD. For PLS chemometriccalibration a concentration set of random mixture consisting of the two drugsin ethanol was prepared. The absorbance data in UV spectra and their dA/dl values were measured for the 24 l points considering Dl= 4 nm. The calibration of the PLS method involvesboth absorbance-concentration and dA/dl-concentration data matrices. The numerical valueswere calculated by using Matlab version 6.5 and origin 7.0 software. Theresults of the methods were statistically compared with each other and a goodharmony was found. The developed calibrations were successfully applied forassaying the pharmaceutical formulation of AldorilÒ tablets

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