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Clinical Chemistry, Vol 36, 1750-1755, Copyright © 1990 by American Association for Clinical Chemistry
SA Margolis, RC Paule and RG Ziegler
Organic Analytical Chemistry Division, National Institute for Standards and Technology, Gaithersburg, MD 20899.
We describe a rapid method for accurately and precisely measuring ascorbic acid and dehydroascorbic acid in plasma. Total analysis time is less than 10 min, replicate analyses of a single pool provide precision less than or equal to 2%, and values measured in supplemented samples agree with known concentrations of 4.68 and 11.83 mg/L. The stability and homogeneity of lyophilized plasma samples supplemented with ascorbic acid and dithiothreitol are documented. We also describe a procedure in which metaphosphoric acid (50 g/L) is used to prepare a reference material for the measurement of ascorbic acid and dehydroascorbic acid. The procedure for both acids consists of first measuring the native ascorbic acid, then reducing the dehydroascorbic acid, at neutral pH, with dithiothreitol, and finally measuring the total ascorbic acid; dehydroascorbic acid is then determined by difference. The metaphosphoric-acid-treated samples were stable at -70 degrees C, but stability decreased with temperature over the range examined, 4-50 degrees C.
The following articles in journals at HighWire Press have cited this article:
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S. A. Margolis and E. Park Stability of Ascorbic Acid in Solutions Stored in Autosampler Vials Clin. Chem., August 1, 2001; 47(8): 1463 - 1464. [Full Text] [PDF] |
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