Description Application Phthaldialdehyde has been used: • in the preparation of O-phthaldialdehyde reagent for analysing gentamycin content[1] • in the preparation of reagent for determining the degree of hydrolysis of milk proteins[2] • in the measurement of free amino acids of milk samples by O-phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC) assay[3] • in the derivatization of putrescine samples[4] For precolumn derivatization of amino acids for HPLC separation. For flow cytometric measurements of protein thiol groups.