QUANTITATIVE DETERMINATION OF ASCORBIC ACID CONTENT IN DIETARY SUPPLEMENTS BY TITRIMETRIC AND SPECTROPHOTOMETRIC METHODS
DOI:
https://doi.org/10.11603/mcch.2410-681X.2026.i2.16331Keywords:
ascorbic acid; vitamin C; titrimetric analysis; iodometry; iodatometry; iodchlorometry; spectrophotometry.Abstract
Introduction. Ascorbic acid (vitamin C) is an important biologically active component involved in many physiological processes. Consequently, dietary supplements containing vitamin C are widely used for the prevention of hypovitaminosis. Quality control of such supplements involves determining the actual content of ascorbic acid and verifying its contents with the declared value. Various analytical methods (classical and optical methods of analysis) are used for this purpose. The selection of an appropriate analytical procedure allows for the assessment of the quality of pharmaceutical products and dietary supplements, as well as ensuring their compliance with the requirements of regulatory documentation and quality standards. The aim of the study – to quantitatively determine ascorbic acid in dietary supplements using redox and spectrophotometric methods of analysis, and to compare the obtained results with the declared content. Materials and methods. Ascorbic acid was determined by using titrimetric methods with different type of titrants, which based on redox reactions involving ascorbic acid. Additionally, a spectrophotometric method was used to confirm the presence of ascorbic acid in the test samples. Results and discussion. The results of the studies showed that the ascorbic acid content in samples from different manufacturers falls within the range of minor deviations, but the obtained values depend on the determination method. For sample 1, the results are close to each other for all applied methods, reflecting good reproducibility and the absence of a significant influence of excipients on the course of the reaction. For sample 2, greater variability of results is observed when using I2 and KIO3 as the titrant are practically identical, a slight lower values of results are observed at using ICl, which may be due to the influence of other substances in the sample. It was found that for sample 3, the usage of ICl yields lower results compared to other methods. Spectrophotometric determination confirmed the presence of ascorbic acid in all samples, consistent with the titrimetric methods. Conclusions. As a result of the study, it was found that the ascorbic acid content in dietary supplements lies within a narrow range of values and depends on the method of analysis. The most reliable results were obtained using KIO₃, while spectrophotometric analysis confirmed the existing vitamin C content, which substantiates the need for using some different methods.
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