Measurement of ascorbic acid and dehydroascorbic acid in gastric juice by HPLC

✍ Scribed by M. J. Sanderson; C. J. Schorah

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 715 KB
• Volume: 2
• Category: Article
• ISSN: 0269-3879
• DOI: 10.1002/bmc.1130020506

✦ Synopsis

New methods are presented for measuring total vitamin C and the ascorbic acid/dehydroascorbic acid ratio in gastric juice. Extracts are prepared from a gastric juice which are suitable for direct injection onto a Waters Nova-pak C , , Radial-pak cartridge for high performance liquid chromatography (HPLC) using ultraviolet absorbance at 270 nm for detection. Both enable removal of interfering mucus and mucopolysaccharide breakdown products in a novel way. The first uses mini-columns of Sephadex G-50, run in acidic conditions to remove large molecular weight material while maintaining the ascorbic acid/dehydroascorhic acid ratio as it was in the fresh sample. Addition of dithiothreitol converts the dehydroascorbic acid quantitatively to ascorbic acid, thus enabling measurement of both components. The second method converts all the dehydroascorbic acid to ascorbic acid at the outset. A perchloric acid extract is neutralized and passed through a Sep-Pak C,s. A new internal standard, reductic acid, is introduced for ascorbic acid analysis which behaves identically on Sep-Pak CIS. Samples are analysed by ion-pair chromatography using 0.02 M NH4H2P04 buffer (pH 7.1): methanol (80 : 20 v/v) containing 0.62 g/L tetrapentylammonium bromide. The detection limit was 1 ng ascorbic acid, and chromatography was completed in 5 min. The values obtained by the two independent HPLC methods were in good agreement with each other and with those obtained by the 2,4-dinitrophenylhydrazine colorimetric method.