RAMAN SPECTROSCOPIC AND POTENTIOMETRIC STUDIES OF ACIDITY LEVEL AND DISSOCIATION OF CITRIC ACID IN AQUEOUS SOLUTION
M. A. ELBAGERMI *
Department of Chemistry, Faculty of Science, University of Misurata, P.O. Box, 1338 Misurata, Libya
A. I. ALAJTAL
Department of Chemistry, Faculty of Science, University of Misurata, P.O. Box, 1338 Misurata, Libya
H. G. M. EDWARDS
Raman Spectroscopy Group, University Analytical Centre, Division of Chemical and Forensic Sciences, University of Bradford, West Yorkshire, BD7 1DP, UK
G. H. AZIMI
Department of Chemistry, Faculty of Sciences, University of Arak, Arak 38156, Iran
K. D. VERMA
Department of Physical, S.V. (P.G) College, Aligarh-202001, India
I. J. SCOWEN
Raman Spectroscopy Group, University Analytical Centre, Division of Chemical and Forensic Sciences, University of Bradford, West Yorkshire, BD7 1DP, UK
*Author to whom correspondence should be addressed.
Abstract
The dissociation constant is one of the most important characteristics of a pharmaceutical chemical moiety which has to be estimated with accuracy. The development of in-situ speciation methods in solutions with parallel measurements using Raman spectroscopy (molecular) and pH (macroscopic) for the identification, characterization, and quantitative determination of citric acid species in aqueous solution by numerical data treatment using a multiwavelength curve fitting program over a range of pH values is described. As a result, the first, second and third stepwise dissociation constants of citric acid have been evaluated as 3.02±0.06, 4.78±0.06 and 6.02±0.04, respectively. From these data over the pH range 2.38-6.16 an excellent agreement with literature values was achieved.
Keywords: Raman spectroscopy, citric acid, dissociation constants, multiwavelength, potentiometric