Fig. 3.

Effect of (a) pH and (b) temperature on the relative activities of trypsin in solution (circles) and trypsin immobilized on an APTES/CMD/AMD-modified fused-silica surface (triangles). In b the maximum insulin B conversion rate determined under experimental conditions is 4.41 ± 0.02 pmol min⁻¹ μg⁻¹ for the enzyme in solution and 12.32 ± 0.35 pmol min⁻¹ μg⁻¹ for a 3-μL, 50-μm i.d. microreactor operated at a flow rate of 1 μL min⁻¹