Spectrophotometric determination of Ethionamide in Pharmaceuticals using Folin-Ciocalteu reagent and Iron (III)-Ferricyanide as Chromogenic Agents
Authors: Nagib A.S. Qaraha, Kanakapura Basavaiaha, Sameer A.M. Abdulrahman
Abstract:
This study presents two spectrophotometric methods that are both simple and sensitive for the determination of ethionamide (ETM) in pure drug form and tablets. The first method utilizes the reduction of Folin-Ciocalteu (F-C) reagent by ETM in a sodium carbonate medium, resulting in the formation of a blue-colored complex that can be measured at 760 nm (referred to as the Molybdenum-tungsten blue method). The second method, known as the Prussian blue method, involves the reduction of iron (III) to iron (II) by ETM in an HCl medium. The formed iron (II) is then complexed with ferricyanide, leading to the formation of Prussian blue, which is also measured at 760 nm. The measured absorbance in both methods is directly proportional to the concentration of ETM.
Extensive experimental investigations were conducted to carefully study and optimize the experimental conditions for both methods. The Beer's law was observed in the concentration ranges of 1–40 μg/ml and 0.2–4.0 μg/ml for the Molybdenum-tungsten blue method and Prussian blue method, respectively. The corresponding molar absorptivity values were found to be 5.72 × 10^3 and 3.18 × 10^4 l/(mol·cm). The limits of detection (LOD) and quantification (LOQ) for the Molybdenum-tungsten blue method were determined as 0.09 and 0.27 μg/ml, respectively, while for the Prussian blue method, they were 0.01 and 0.04 μg/ml, respectively. The precision of the methods was evaluated by calculating the within-day and between-day relative standard deviations (%RSD) at three different concentration levels, which were found to be less than 3%. Additionally, the respective relative errors (%RE) were ≤ 2%, indicating good accuracy and precision of the methods.
To validate the suitability of the proposed methods, they were successfully applied to the determination of ETM in bulk powder and tablets. The results obtained demonstrated that the developed methods were as accurate and precise as the official method for the analysis of ETM.
Keywords
Ethionamide; Folin-Ciocalteu reagent; Iron (III); Ferricyanide; Spectrophotometry; Pharmaceuticals
Citation: Nagib A.S. Qaraha, Kanakapura Basavaiaha, Sameer A.M. Abdulrahman Spectrophotometric determination of Ethionamide in Pharmaceuticals using Folin-Ciocalteu reagent and Iron (III)-Ferricyanide as Chromogenic Agents http://dx.doi.org/10.1016/j.jtusci.2016.07.002.
Received: 27 March 2016, Revised: 27 June 2016, Accepted: 19 July 2016, Available online: 31 August 2016
Copyright: © 2016 Elsevier B.V. or its licensors or contributors. Open Access funded by Taibah University
Conclusion
The spectrophotometric methods described in this article were found to be simple without involving any critical experimental variable compared to most reported methods. The methods were demonstrated to be both accurate and precise besides being robust and rugged. Both systems have wide linear dynamic ranges of applicability, and the Prussian blue method with an ? value of 3.18 × 104 l mol−1 cm−1 is the most sensitive one ever reported for ETM (Table 6). The reference method [4] requires scrupulously anhydrous medium for accurate end point detection, besides generating a large quantity of organic solvent as waste. This creates the problem of waste disposal, and hence it is not a green method further, the reference method is applicable to macro scale (300 mg drug per trial). In contrast, the proposed methods seldom employ organic solvents, and applicable over micro scale (μg/ml). These advantages coupled with the use of cheap and readily available chemicals and simple instrumentation, make the methods suitable for use in quantity control laboratories of developing and under developed countries which would ill-afford the expensive techniques like HPLC and others.
Acknowledgement
The gift sample of Ethionamide by Panacea Biotec Ltd. is gratefully acknowledged. Prof. K. Basavaiah wishes to thank the University Grants Commission, New Delhi. India, for the award of BSR faculty fellowship. The first author is thankful to the UGC New Delhi, India for financial assistance through Junior Research Fellowship.
