development and validation of different spectrophotometric and TLC methods for determination of fosinopril sodium, hydrochlorothiazide, and chlorothiazide
Research Abstract
Three simple, sensitive, and validated methods were developed
for the quantitative determination of fosinopril sodium (FOS) and
hydrochlorothiazide (HCZ) in the presence of an HCZ impurity,
chlorothiazide (CZ). The first method (I) was the ratio difference
spectrophotometric method (RD), in which a standard spectrum of
8 μg mL−1 HCZ was used as a divisor, and the difference in amplitude values at 204.6 and 231.2 nm and 290 and 302.6 nm was used
for the determination of FOS and CZ, respectively. Meanwhile, for
the determination of HCZ, a standard spectrum of 6 μg mL−1 CZ
was the chosen divisor, and the amplitude difference at 275 nm and
293.6 nm was selected for the calculation of its concentrations. The
second method (II) was mean centering of ratio spectra spectrophotometric method (MCR), which depended on the implementation of the mean-centered ratio spectra in two successive steps and
the measurement of the amplitudes of the mean-centered second
ratio spectra at 243.4 nm for CZ and peak-to-peak amplitudes at
215.6 and 215.8 nm for FOS and at 223.8 and 224 nm for HCZ. On
the other hand, the third method (III) was thin-layer chromatography (TLC)‒densitometry at which the chromatographic separation
of this ternary mixture was performed using pre-activated silica
gel 60 F254 TLC plates and a developing system mixture consisting
of ethyl acetate‒chloroform‒methanol‒formic acid (60:40:5:0.5, by
volume) with ultraviolet (UV) scanning at 215 nm. The developed
methods were validated according to the International Conference
of Harmonization (ICH) guidelines and were successfully used for
the determination of FOS and HCZ in their pharmaceutical formulations.
Research Keywords
fosinopril sodium