Copper(II) on Chitosan (Cu 1.3mmol/g)

Copper (II) on chitosan is a chitosan-supported copper (II) (about 1.3 mmol/g) developed by Inoue et al. as a reagent for selective detection of reducible organic compounds. The Cu (II) on chitosan can selectively detect reducible organic compounds bearing structures changeable to ene-diolate (e.g. glucose, ribose) in basic aqueous solution with the formation of copper (I) oxide (Cu₂O) as a signal of the reduction by the ene-diolate.

(The color of Cu (II) on chitosan is subject to change to green after opening. But the green-colored Cu (II) on chitosan changes to dark blue which is suitable for this detection in basic aqueous solution, in the same way as a new reagent.)

Typical procedure (detection of a sugar): A test tube (15 mm inside diameters) is charged with copper (II) on chitosan (20 mg) and an aqueous solution of 0.5 mol/L NaOH (1 mL). At this point, the color of copper (II) on chitosan changes from blue to dark blue. Then, an aqueous solution of 10 mmol/L sugar (4 mL) is added, and the mixture is stirred at 70 to 80 °C for 5 min.
If it gives a positive result, red-brown to orange colored Cu₂O on chitosan is observed (e.g. glucose and ribose). If it gives a negative result, black to blue colored CuO on chitosan is observed (e.g. 2-deoxyglucose and 2-deoxy ribose).

Using Cu (II) on chitosan, needs a lesser amount of Cu (II) than that of Fehling and Benedict reagents and leads to significantly reducing the reagent costs and waste chemicals. In addition, Cu (II) on chitosan is a powdery substance, which is easily handled and free from leaking in carrying and storage. Notably, Cu (II) on chitosan is suitable for science educational experiments such as a test for the detection of a reducing sugar yielded from starch hydrolysis.