A new simple and reliable spectrophotometric method is described to determine glyoxylic acid in its synthesis reaction mixture containing oxalic acid, glycolic acid, acetic acid, glyoxal, and ethylene glycol by means of a modified Hopkins–Cole reaction between glyoxylic acid and tryptophan in presence of ferric chloride and concentrated sulphuric acid. The linear range of glyoxylic acid concentration is 0–0.028 M. The limits of detection (LOD) and quantitation (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 dialdehyde.

中文翻译：

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一种简单的分光光度法测定合成混合物中的乙醛酸。

描述了一种新的简单可靠的分光光度法，通过在乙醛酸和色氨酸之间存在修饰的霍普金斯-科尔反应，通过测定乙醛酸，色氨酸和色氨酸之间合成的乙醛酸，乙醛酸，乙二醛和乙二醇的合成反应混合物中乙醛酸的含量，氯化铁和浓硫酸。乙醛酸浓度的线性范围为0–0.028M。检测限（LOD）和定量限（LOQ）分别为0.0019 M和0.00577M。该方法的LOD，LOQ，标准偏差，相对标准偏差和回收率与所选的HPLC参考方法相当。两种方法都显示出相同的精度和可信度。色氨酸和乙醛酸之间的反应化学计量假设为2：3。已经基于确定的反应物摩尔比推测了反应机理。乙二醛虽然是二醛，但对色氨酸的测试结果为阴性。