Confirmatory Test for Chitosan

Question

Okay heres my problem. I cannot find this procedure online, can someone please help me?

Confirmatory Test for Chitosan Reagents and materials: Iodine/Potassium iodide (0.2 g iodine are added to 100 ml of a potassium iodide solution, w(KI) = 5%) and sulfuric acid = 1%

Small amount of chitosan powder was dissolved in water using a test tube. Distilled water was placed in half of another test tube. Then mix the dissolved chitosan solution in the distilled water test tube. 2-3 drops of Iodine/Potassium iodide was added. The mixture was then acidified with 3-6 drops of sulfuric acid. The solution was mixed using a stirring rod. After the addition of Iodine/Potassium iodide, the precipitate turned dark brown. On the addition of sulfuric acid, the dark brown color turned to dark purple. This indicates the presence of chitosan (Lande et al., 2015).

Answer 1

You might be looking for the Van Wisselingh test for chitosan.

"Van Wisselingh test. This test is also called the 'chitosan-iodine test for chitin'. It is based on the hydrolysis of chitin to chitosan in the deacetylation process. While natural chitin does not react in this reaction, chitosan reacts with iodine, giving brown colored adduct. For chitin, the color seems black, but after a more thorough examination, it is reddish-purple."

See also ResearchGate, Complex Formation of Chitosan with Iodine and Its Structure and Spectroscopic Properties--Molecular Assembly and Thermal Hysteresis Behavior, which is available for download sans paywall.