Quantitative Analysis by IR: Determination of Chitin/Chitosan DD DOI: http://dx.doi.org/10.5772/intechopen.89708

#### Table 9.

corresponding onium hydroxide (Q<sup>+</sup> OH�) capable of diffusing from the aqueous phase to the organic phase to start the deacetylation process by attacking the C = O of the acetyl group and then at the end of the reaction of hydrolysis, the resulting

to a new onium hydroxide by the reaction with NaOH. From our results, the DD/ CNaOH ratios remain constant at each temperature at longer deacetylation times,

The results obtained under various conditions were analyzed statistically using multilinear regression analysis (uncertainty value =0.05) [23]. The NaOH concentration, temperature, and reaction time were chosen as independent parameters for the three-variable and three-level (maximum, mean, and minimum) factorial design. The best equation obtained for the chitosan extraction process in this study is Eq. (6). Shrimp at a higher temperature is not reliable. In addition, the production of chitosan at high temperature causes degradation of the container and therefore involves manipulations more difficult to adapt for industry. To ensure the quality of the chitosan product, the digestion temperature must be kept constant at 110°C.

6. IR statistic study for optimization of deacetylation conditions

%DD ¼ 72, 56 þ 5, 6 ∗ ð Þþ NaOH 3, 78 ∗ ðtemperatureÞ þ 24, 86 ∗ ð Þ temps

The values of this equation indicate that the effect of three factors studied influences DD in the following order: reaction time (24.86) > NaOH concentration (5.6) > reaction temperature (3.78). Further, a reaction time of 152 min (≈2.5 h) is predicted from Eq. (5) to reach 90% DD using a NaOH concentration of 12.5 M and a temperature set at 110°C. This time predicted by the factorial plane seems consistent with the actual deacetylation reaction time (120 min) with an error of 27%. The production of chitosan from dried shrimp exoskeletons can be done in 1 day instead of the 3 days required by the conventional method. The results obtained show that the extracted chitosan has a DD greater than 90% under optimal conditions by the hydrothermal-chemical technique in two stages at 110°C, that is, 11.25 M NaOH for 3 h or 12.5 M NaOH during 2 h. For the extraction of chitosan at an SD of 85% in the context of water treatment, the transformation procedure must

• Deproteinization and deacetylation at 110°C with 11.25 M NaOH for 2 h

A new method of producing very high DD content chitosan under low concentration alkaline conditions has been introduced by Xiaofei et al. [79]. The synthesis was produced at high temperatures and pressures. The results in Table 9 were deduced from IR spectra. Compared to traditional methods, low concentration alkaline and short reaction time are excellent benefits. In addition, compared to the enzymatic and organic solvent treatment method, the pressure method was inexpensive and convenient without further purification. Excellent repeatability and simplified operation increased its availability in production and large application

7. Deacetylation of chitin by compression method study by FTIR

� 11, 92 ∗ ð Þ temps (6)

which means that the deacetylation reaction is complete.

be carried out under the following optimal conditions:

• Demineralization at 50°C for 2.5 h in 2 M HCl

118

) will diffuse into the aqueous phase to be regenerated

onium acetate (CH3COO�Q<sup>+</sup>

Modern Spectroscopic Techniques and Applications

The effect of different reaction conditions on DD value of chitosan [79].

chitosan scale with large quantity production. In order to produce chitosan with a very high content of DD by chitin in a more efficient and more environmentally friendly way, Xiaofei et al. [79] have changed the pressure and have used the multistep method for the deacetylation of chitin in alkaline at low concentration. They adopted the alkaline recycling model using alkaline waste in the next deacetylated step. In this model, they added an alkali according to the different demands of each phase and eliminated acetyl in a timely manner, in case the high concentration of the acetyl group would inhibit the deacetylation. In addition, the use of the base in several steps will be effective not only to control the degree of deacetylation but also to control the molecular weight of the resulting product.

Working under high pressure and with low concentrations of the base, they were able to extract chitosan with DD of 100%. In fact, only 15% of alkali solution and a ratio of 1:10 chitosan powder to NaOH solution and to a pressure of less than 0.11–0.12 MPa for 120 min lead to 100% DD. When the alkali concentration varies from 5–15%, the very high value DD chitosan (up to 95%) is produced. The method under pressure to prepare 100% deacetylated chitosan with less environmental pollution is very interesting.
