Tropical Journal of Pharmaceutical Research
Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, Nigeria
Vol. 14, No. 3, 2015, pp. 519-525
Bioline Code: pr15068
Full paper language: English
Document type: Research Article
Document available free of charge
Tropical Journal of Pharmaceutical Research, Vol. 14, No. 3, 2015, pp. 519-525
© Copyright 2015 - Tropical Journal of Pharmaceutical Research
Visible Spectrophotometric and Thermodynamic Studies of Diclofenac: Charge-Transfer Complexation with 2, 3 Dichloro-5, 6-dicyano, 1, 4-benzoquinone|
Uzochukwu, Ikemefuna C. & Nzegbunam, Stanley O.
Purpose: To investigate the visible spectrophotometric and thermodynamic parameters of diclofenac
with regard to charge-transfer complexation with 2, 3-dichloro-5, 6-dicyano-1, 4-benzoquinone.
Methods: The wavelength of maximum absorption, stoichiometry, time-absorbance relationship, effect
of pH, Beer’s plot and Beer’s law limit for the complex were evaluated for diclofenac. In order to validate
an assay method based on the complexation reaction, the limit of detection and quantitation, precision,
accuracy and selectivity were determined. The developed assay method was applied to the assay of
diclofenac tablet and capsule brands.
Results: A 1:1 complex that absorbed maximally at 506 nm and a Beer’s plot with a regression
coefficient of 0.9970 ± 0.0010 were obtained. Beer’s law was obeyed in the concentration range of
0.0017 to 0.2111 mg/ml and precision was within acceptable limits. The limits of detection and of
quantitation of the method was 0.000801 and 0.002426 mg/ml, respectively. The spontaneity of the
complexation reaction was demonstrated by negative Gibb’s free and positive entropy energy changes.
The drug content of commercial diclofenac products to which the assay method was applied was
between 94 and 102 %.
Conclusion: Charge-transfer complexation of diclofenac with 2, 3-dichloro-5, 6-dicyano-1, 4-
benzoquinone is straightforward, and the assay method based on it is simple and robust for the
determination of diclofenac in tablet or capsule formulation.
Spectrophotometry; Charge transfer complex; Diclofenac; Tablets; Capsules; Validation
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