13] - Determination of Formic Acid in the Periodate Oxidation of Carbohydrates

Abstract

Publisher Summary This chapter focuses on the determination of formic acid in the periodate oxidation of carbohydrates. Several methods are now available for the determination of formic acid liberated by periodate oxidation along with the methods involving direct titration with alkali, liberation and titration of iodine from a solution of iodide and iodate, and manometric determination of carbon dioxide liberated from a bicarbonate buffer. Any acidic groups originally present—for example, as in a glycoprotein—may contribute to the results from these methods although a correction factor can be obtained from a blank estimation under the same conditions of the parent compound treated with periodate previously destroyed with ethylene glycol. The titrimetric methods often suffer from fading end points and titration curves nonidentical to formic acid; in addition, iodine may complex with some structures. The manometric method is experimentally difficult to use, its chief advantage being in the continuous monitoring of formic acid release without sampling. Manometric methods involving oxidation of formic acid to carbon dioxide by lead tetra acetate, eerie sulfate, or mercuric chloride are similarly unsuitable and nonspecific. Steam distillation is sometimes used to overcome the specificity problem, but this is not an easy procedure and formic acid not produced by the oxidation may be liberated.