Detection of polyols and sugars by cuprammonium ion in the presence of strong base.

A new and more sensitive cuprammonium reagent containing strong base has been developed for the colorimetric detection of polyols and sugars. A reagent blank with an absorbance at 280 nm, less than half that of previous methods, was achieved by reducing the cupric ion and ammonia concentrations to 1 mM (from 5 mM) and 0.4 M (from 2.25 M), respectively, and adding 0.2 M sodium hydroxide. Polyols are particularly well suited to the new method, showing up to an eightfold increase in sensitivity. The new reagent is readily applicable to the postcolumn detection of polyols and sugars after high-performance liquid chromatography and is linear over the range 40-180 nmol for D-glucitol (sorbitol) and 10-300 nmol for glucose, using standard HPLC equipment.