Introduction
Ascorbic acid, an important water soluble vitamin, is highly sensitive to heat, alkali, oxygen and light (1). Its rapid degradation in aqueous solutions, especially upon exposure to light, clearly complicates the assay studies. We have demonstrated that the formation of binary and multicomponent complexes with HP-b-CD and TEA strongly reduced the photodegradation process in solution (2). This fact appears to be of great interest for the assay of the vitamin, due to the exposure of the solutions to light over prolonged periods of time.
In this study, based on the significant enhancement of the stability and photostability of ascorbic acid in aqueous solutions due to the formation of complexes, an HPLC method for its determination was developed and validated
Materials and methods
All chemicals used were of analytical grade and the solvents were HPLC grade. Analyses were performed using an Agilent 1100 series system.
The method was validated according to ICH guideline.
The results obtained by applying the developed method for the estimation of the drug in pharmaceutical formulations, are compared with those found using the reference method (3).
Results and discussion
Under the experimental conditions, good linearity of the calibrations was established. Recovery studies on intra-day and inter-day experiments showed satisfactory repeatability, intermediate precision and accuracy.
Ascorbic acid in the commercial formulations analyzed was found in the range of 81.0?100.2%, compared to the declared values. The reported relative standard deviation (R.S.D.) values reflected the high precision of the proposed method when is applied to the assay of commercial pharmaceuticals, in comparison with those obtained by the reference method.
Furthermore, these studies confirm that the formation of complexes allows the obtention of reliable analytical results, due to the increase in the stability and the photostability of ascorbic acid during the preparation of the samples and their later analytical assay.
Conclusions
A chromatographic method was developed in the presence of the ligands HP-b-CD and TEA, without loss of ascorbic acid during preparation of the analytical samples and the assay. All the validation parameters were found satisfactory, after which, the method was applied to the determination of drug in pharmaceutical formulations.
The developed methodology represents a great improvement over the reference method, which requires more preparation time and standardization of the titration solutions. In addition, this method requires a simple sample preparation procedure, decreasing the degree of uncertainty and the time of the assay. So, they provide high throughput solution for the determination of ascorbic acid, either in the pure form or in pharmaceutical formulations.
Acknowledgments
We thank Ferromet
References
(1) Connors K, Amidon A, Stella V. Chemical Stability of Pharmaceuticals, A Handbook for Pharmacists. 2nd ed. New York : John Wiley & Sons; 1986.
(2) Garnero C, Longhi MR. Development of HPLC and UV spectrophotometric methods for the determination of ascorbic acid using hydroxypropyl-b-cyclodextrin and triethanolamine as photostabilizing agents. Anal. Chim. Acta 2010; 659: 159-166.
(3) United States Pharmacopeia XXX (NF 25), United States Pharmacipeial Convention. MD, USA: Rockville; 2007.
