This chapter emphasizes the separation of L-ascorbic acid (AA) and D-erythorbic acid (EA) from their respective oxidation and hydrolysis products by weak anion-exchange high- performance liquid chromatography (HPLC). The primary basis for the physiological roles of vitamin C is the oxidation–reduction system between AA and L-dehydroascorbic acid (DHAA). EA is epimeric to AA at C-5 and possesses little or no vitamin C activity; it may be an antagonist of vitamin C. The high-performance liquid chromatography (HPLC) separation of AA, EA, L-diketogulonic acid (DKGulA), and D-diketogluconic (DKGluA) on aminopropyl bonded-phase silica is accomplished by weak anion-exchange chromatography with acetonitrile–0.05 M KH2PO4 eluant. The conjugated enediol chromophore in AA and EA allows their detection at 270 nm; reduction of DHAA and D-dehydroerythorbic acid (DHEA) with dithiothreitol (DTT) allows their indirect determination from the increase in AA and EA absorption. In aqueous solution, DHAA exists as a hydrated bicyclic hemiketal and in DKGulA both ketone functions are hydrated. Refractive index detection is the method of choice for the compounds considered, especially with the recent development of highly sensitive detectors. Series: Methods in Enzymology (Book 122) Hardcover: 496 pages Publisher: Academic Press; 1 edition (April 11, 1986) Language: English ISBN-10: 012182022X ISBN-13: 978-0121820220 Product Dimensions: 6 x 9 inches Link Download http://nitroflare.com/view/79ABECE1F61F060https://drive.google.com/drive/folders/1yLBzZ1rSQoNjmWeJTZ3WGQHg04L1
