>98% [HPLC]. Free PNP < 0.1%.
alpha-D-galactosidase substrate: K. Wallenfels, Methods in Enzymology, V, 212 (1962). Galactosyl donor in oligosaccharide synthesis: G. Vic et al., J. Chem. Soc., Chem. Commun., 169 (1997).