SIMULTANEOUS DETERMINATION OF HYDROCHLOROTHIAZIDE AND METHYLDOPA IN TABLETS USING FIRST DERIVATIVE SPECTROPHOTOMETRY AND PLS

Document Type : Original Article

Author

Chemistry Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt

Abstract

Two new analytical methods are described as
convenient and useful alternatives for simultaneous determination of
hydrochlorothiazide (HCTZ) and methyldopa (MD) in their combinations. The first
method depends on the first order derivative spectrophotometry by measuring the
amplitudes at zero-crossing wavelengths of 286 and 270 nm for HCTZ and MD,
respectively. In the second method, partial least squares (PLS) analysis of the
ultraviolet absorption spectra of the samples in the 240-340 nm region was
applied. 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 chemometric
calibration a concentration set of random mixture consisting of the two drugs
in 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 involves
both absorbance-concentration and dA/dl-concentration data matrices. The numerical values
were calculated by using Matlab version 6.5 and origin 7.0 software. The
results of the methods were statistically compared with each other and a good
harmony was found. The developed calibrations were successfully applied for
assaying the pharmaceutical formulation of AldorilÒ tablets

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Al-Azhar Bulletin of Science
Volume 18, Issue 2-A
December 2007
Pages 113-126

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