A specific method for D-galactose quantitative determination: a modification of the D-galactose oxidase assay

After treatment with D-galactose oxidase to form an aldehyde group, D-galactose or 2-acetamido-2-deoxy-D-galactose reacted with indole-hydrochloric acid to give a colored compound having a spectrum very similar to that of D-galacturonic acid, but with a maximum at 500 nm and a shoulder at 480 nm. The reaction is linear between 16.6 and 83 nmol of sugar per mL of final solution. 2-Amino-2-deoxy-D-galactose gave no reaction, even when 5 mumol were used, and 2-deoxy-D-lyxo-hexose did not interfere either.