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.

A submitted manuscript to International Journal of Analytical Chemistry:<div><br><div>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. </div></div>

A submitted manuscript to International Journal of Analytical Chemistry:<div><br><div>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. </div></div>

The adverse effects of acrylamide (AA) on humans are being clear, especially after a series of related investigations reported the dependance of consuming foods that prepared by exposing to high temperature for a long-time and cancer risk. Accurate determination of AA in food samples at trace amount is considered the first step to overcome this significant problem. The determination of AA using coal tar pitch modified pencil graphite (PGE/CTP) electrode was reported. The electrochemical behavior of AA was studied on PGE/CTP electrode in different medium acidities (pH) of phosphate and Briton-Robinson (BR) buffer solutions by employing square wave voltammetry (SWV). Linear sweep voltammetry (LSV) technique was applied to determine the mass transfer mode of AA from bulk solution to the PGE/CTP electrode surface. The optimum conditions were using phosphate buffer solution (PBS) at pH 7.0. The linear relationship among peak current and AA concentration was in the range 1000.0 nM to 0.5 nM. The limit of detection for detection of AA was 0.2094 nM and the limit of quantitation for quantification was 0.6912 nM. In addition, the PGE/CTP electrode as the sensor was successfully used for the determination of AA in instant coffee sample.