Original
Research Article
Spectroscopic Studies
of the Electron Donor-Acceptor Interaction of
Chloroquine Phosphate with Chloranilic Acid
KC Ofokansi1*,
EO Omeje2, and CO Emeneka1
1Department
of Pharmaceutics, 2Department of
Pharmaceutical and Medicinal Chemistry, Faculty of
Pharmaceutical Sciences, University of Nigeria, Nsukka
410001, Enugu State, Nigeria
*Corresponding
author:
Tropical
Journal of Pharmaceutical Research, February
2009; 8(1):
87-94
Abstract
Purpose:
The electron donor-acceptor interaction between drugs
which act as electron donors and some electron-deficient
compounds (π acceptors) has severally been utilized as
an analytical tool for the quantitation and qualitative
assessment of such drugs. The objective of this study,
therefore, was to develop an assay procedure for dosage
forms of chloroquine phosphate based on its reaction
with chloranilic acid which resulted in the formation of
a charge-transfer complex.
Methods:
The complex formation between chloroquine phosphate and
chloranilc acid as evidenced by the instantaneous change
in colour of a solution of chloranilic acid in dioxan
from yellow to purple upon addition of a solution of
chloroquine phosphate in chloroform was monitored
spectrophotometrically to determine the wavelength of
maximum absorption. The stoichiometry of the complex
formed was evaluated using the Job’s continuous
variation method while the thermodynamics of the complex
was evaluated spectrophotometrically with the aid of the
Benesi-Hildebrand plot.
Results:
Spectrophotometric absorption studies showed evidence of
the formation of strongly bonded and highly stable
charge-transfer complex between chloroquine phosphate
and chloranilic acid in a 3:2 stoichiometry in
non-aqueous medium. The transitions involved were
detected at wavelengths longer than those of the
individual pure substances in the visible region of the
spectrum. Conformity with Beer’s law was evident over
the concentration range 0.8 – 8.0 mg/100 ml
of chloroquine phosphate; thus making it possible for
an accurate quantitative determination of the drug.
Conclusion:
The studied complexation phenomenon formed a basis for
the quantitative determination of both pure samples and
individual dose units of chloroquine phosphate and is
considered a simple, sensitive and precise analytical
tool with high accuracy for routine analysis of
chloroquine phosphate in developing countries where
sophisticated analytical instruments may not be
available.
Keywords:
Spectroscopic studies,
Electron Donor-Acceptor Interaction, Chloroquine
phosphate, Chloranilic acid.
