Introduction: Spectrophotometry was investigated for the determination of epsilon aminocaproic
acid (EACA) with p-nitrophenol (PNP). The method was based on Charge Transfer (CT)
complexation of this drug as n-electron donor with π-acceptor PNP.
Methods: The experiment indicated that CT complexation was carried out at room temperature for 10
minutes in dimethyl sulfoxide solvent. The spectrum obtained for EACA/PNP system showed the maximum
absorption band at a wavelength of 425 nm. The stoichiometry of the CT complex was found to
be a 1:1 ratio by Job’s method between the donor and the acceptor. Different variables affecting the
complexation were carefully studied and optimized. At the optimum reaction conditions, Beer’s law
was obeyed in a concentration limit of 1～6 μg mL-1. The relative standard deviation was less than
2.9%. The apparent molar absorptivity was determined to be 1.86×104 L mol-1cm-1 at 425 nm. The CT
complexation was also confirmed by both FTIR and 1H NMR measurements.
Results: The thermodynamic properties and reaction mechanism of the CT complexation have been
Conclusion: The developed method could be applied successfully for the determination of the studied
compound in its pharmaceutical dosage forms with good precision and accuracy compared to the official
method comprising t- and F-tests.