Glyoxylic Acid Separation from Products of Glyoxal Oxidation in the Form of its Calcium Salt

Abstract

Synthesis of glyoxylic acid was carried out by oxidation of glyoxal aqueous solutions by nitric acid. Glyoxylic acid and oxalic acid (as a by-product) were isolated from technological mixtures in the form of their calcium salts in a strictly defined region of pH. Previously, model calcium salts were synthesized from the commercial acids as reference objects.The results of infrared spectroscopy and complexometric titration of precipitates of calcium salts of glyoxylic and oxalic acids, isolated in various pH regions, allow one to construct reliable research strategies of complex mixtures, such as obtained from the oxidation products of aqueous solutions of glyoxal.

A Simple Spectrophotometric Method for Determination of Glyoxylic Acid in Its Synthesis Mixture

“…e determination of glyoxylic acid in its electrochemical synthesis reaction mixture is a difficult process because this mixture contains carboxylic acids with convergent acidic dissociation constants and other compounds carrying organic groups that can undergo oxidation or reduction such as ethylene glycol, glyoxal, and glycolic acid. us, it is expected that glyoxylic acid will be very difficult to determine quantitatively using traditional analytical methods such as acid-base or redox titrations, separation, or precipitation [2,3].…”

A Simple Spectrophotometric Method for Determination of Glyoxylic Acid in Its Synthesis Mixture

“…Figure (4) shows a proportional increase of absorbance with increasing ferric chloride solution volume up to 1 mL, followed by a slight further increase up to 2 mL ferric chloride addition. Thus, oxidizing agent Optical absorption versus volume of concentrated sulfuric acid in the reagent with 0.25 mL glyoxylic acid 0.028 M, 0.6 mL tryptophan 0.016 M and 2 mL of ferric chloride 0.025 M need to be present in reaction mixture in sufficient amount for satisfactorily performance.To confirm its responsibility for absorption maxima at 440 and 500 nm inFigures (1)and(2), a separate test has been run without addition of ferric chloride solution.…”

“…Thus, it is expected that glyoxylic acid will be very difficult to determine quantitatively using traditional analytical methods such as acid-base or redox titrations, separation, or precipitation [2,3].…”

“…(2) depicts the spectra obtained for 0.028 M glyoxylic acid solution alone and 0.028 M glyoxylic acid in mixture solution using the proposed test procedure. It can be clearly seen that both pure glyoxylic acid and the glyoxylic acid in mixture exhibit practically the same absorbance at 560 nm.…”