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Ascorbic and dehydroascorbic acids measured in plasma preserved with dithiothreitol or metaphosphoric acid.
S A Margolis1, R C Paule, R G Ziegler
1Organic Analytical Chemistry Division, National Institute for Standards and Technology, Gaithersburg, MD 20899.
Clinical Chemistry
|October 1, 1990
Summary
This study presents a fast and accurate method for measuring ascorbic acid and dehydroascorbic acid in plasma. The new technique ensures high precision and reliability for vitamin C analysis in clinical settings.
Area of Science:
- Biochemistry
- Analytical Chemistry
- Clinical Diagnostics
Background:
- Accurate measurement of ascorbic acid (vitamin C) and its oxidized form, dehydroascorbic acid, is crucial for assessing nutritional status and diagnosing related health conditions.
- Existing methods for quantifying these analytes in plasma can be time-consuming and may lack the required precision for routine clinical use.
Purpose of the Study:
- To develop and validate a rapid, precise, and accurate method for simultaneous measurement of ascorbic acid and dehydroascorbic acid in human plasma.
- To establish a stable reference material for quality control in plasma vitamin C analysis.
Main Methods:
- A novel assay involving sequential measurement of native ascorbic acid, reduction of dehydroascorbic acid using dithiothreitol at neutral pH, and subsequent total ascorbic acid determination.
- Preparation and characterization of a stable reference material using metaphosphoric acid (50 g/L) for plasma samples.
- Validation of the method using supplemented plasma samples and assessment of lyophilized sample stability.
Main Results:
- The developed method achieves a total analysis time of under 10 minutes with replicate analysis precision of ≤2%.
- Measurements in supplemented plasma samples showed excellent agreement with known concentrations (4.68 and 11.83 mg/L).
- Lyophilized plasma samples supplemented with ascorbic acid and dithiothreitol demonstrated good stability and homogeneity.
Conclusions:
- The described method offers a rapid, accurate, and precise approach for quantifying both ascorbic acid and dehydroascorbic acid in plasma.
- The metaphosphoric acid-based procedure provides a reliable method for preparing a stable reference material, enhancing quality control in vitamin C measurements.
- The findings support the utility of this method for routine clinical diagnostics and research requiring efficient plasma vitamin C assessment.