... Issue. Archiv der Pharmazie. ... Arch. Pharm., 344: 71–77. ... Various concentrations of PNPG (0.1 to 1.2 mM) as the substrate, 10 µL of α-glucosidase, and 10 mM potassium phosphate buffer (pH 7.0) were added to a test tube in a total volume assay mixture of 1000 µL. ...