I have reacted a known glucose concentration (0.75mg/ml) with 1% w/v DNSA at a mole ratio of 1:1.05 and 1:2.1 mole ratio . The 1:2.1 ratio doesn't completely react i.e. I was expecting to obtain the same concentration of glucose with excess DNS (i.e. 1:2.1) instead I get a 17% lower concentration of glucose than the expected concentration. What could be causing the limitation/hinderance for a complete reaction?