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Dear Stella,

according to my experience if deacetylation degree of chitosan is less than 70%  solubilization in acetic acid solution is not complete or difficult. The following procedure works well and you can have ca. 85% of deacetylation in final product.  

Briefly, 15.0 g of chitin is treated with 720 mL of 40.0% (w/w) aqueous NaOH solution in a 1-L three necked round bottomed flask with reflux condenser connected to its middle neck. A thermometer is connected to control the temperature during the reaction and N2 gas is bubbled through the solution from the side arm to provide inert atmosphere in the reaction medium. Reaction should be performed under constant reflux at 115 ◦C and continued for 6 h.

Or you can apply again your method of deacetylation to the first product. In this way you will be able to increase the total deacetylation of the chitosan. Please check also that concentration of NaOH is w/w not w/v.

Good luck,

Ezel

Dear Stella

A common mistake is to use 40% (w/v) NaOH (i.e. 40 g NaOH in 100 mL water) instead of 40% (w/w) NaOH (i.e. 40 g NaOH in 60 mL water). Also you should increase the time - a general procedure would be 6 hours at 80C. You can actually deacetylate chitin at room temperature but that takes several days minimum.

Best of luck,

George

Dear friends, i am very grateful for your contributions. I will try your methods and inform you later of the results. 

Thank you all.

Dear friend

you need to use 100 c for 5- 10 h

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