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

A new spectrophotometric method is described to determine glyoxylic acid in its synthesis reaction mixture by means of a modified Hopkins-Cole reaction between glyoxylic acid and tryptophan in presence of ferric chloride and concentrated sulfuric acid. The linear range of glyoxylic acid concentration is 0 - 0.028 M. The LOD and LOQ are 0.0019 M and 0.00577 M, respectively. The LOD, LOQ, standard deviation, relative standard deviation and recovery ratio of the proposed method are comparable with a selected HPLC reference method. Both methods displayed same precision and credibility. Reaction stoichiometry between tryptophan and glyoxylic acid is assumed to be 2:3. Reaction mechanism has been postulated based on identified molar ratios of reactants. Glyoxal gave a negative test with tryptophan although it is a di-aldehyde.