8. Deacetylation of chitin under microwave irradiation effect

To extract a large quantity of chitosan, industrialists need high temperatures and chemicals in large quantities. In addition, the conventional process requires a lot of time and consumes a lot of energy, which would harm the environment. Recently, microwave irradiation has been used as an unconventional energy source in chemical reactions. The objective of this study is to synthesis chitosan under microwave


compare IR and other analytical methods to compute DD. The analysis was performed by acidic conductometric assay. Basic conductometric dosing and pH-

9.1 Determination of the degree of deacetylation by conductometric assay

According to Yu et al. [22], the conductometric assay is an adequate and accurate method to determine the degree of deacetylation of chitosan. It was carried out

A solution of chitosan was prepared by dissolving a mass of 150 mg of chitosan in 10 ml of hydrochloric acid (0.1 N) and then the volume was adjusted to 200 ml by addition of distilled water. The prepared solution is titrated with stirring with sodium hydroxide solution (0.1 N). Figure 3A shows the change in the volume of sodium hydroxide as a function of the conductivity of the chitosan solution. The curve has two points of inflection. The difference in the volume of NaOH between these two points corresponds to the amount of HCl required to dissolve the

The degree of deacetylation (DD) of chitosan is then determined from the

where N is the normality of the NaOH solution (mol/l); V2 and V1 are the equivalent volumes of NaOH representing two inflection points, respectively; M is the mass of chitosan; 203 (g/mol) is the molar mass of the acetyl monomer; and 42 (g/mol) is the difference between the molecular weight of the acetyl monomer and

The degree of deacetylation according to the conductometric method is:

(A) Variation of the conductivity of the chitosan solution as a function of the volume of the base (B) variation of

the conductivity of the chitosan solution as a function of the volume of the acid solution.

m þ 42 � ð Þ� V2 � V1 N

0:1 0:15 þ 42 � ð Þ 9:4 � 2:7 :10 � 3 � 0:1

+ .

� 100 (7)

� 100

(8)

chitosan, which is to say to transform the -NH2 groups into -NH3

DD <sup>¼</sup> <sup>203</sup> � ð Þ� V2 � V1 <sup>N</sup>

the molecular weight of the deacetylated monomer.

DD ¼ 203 � ð Þ 9:4 � 2:7 :10 � 3 �

metric dosing techniques will be compared to IR.

DOI: http://dx.doi.org/10.5772/intechopen.89708

Quantitative Analysis by IR: Determination of Chitin/Chitosan DD

in basic and acid medium.

following relationship [70]:

DD ¼ 76:35%:

Figure 3.

121

9.1.1 Basic conductivity measurement

#### Table 10.

Degree of deacetylation (DD), molecular weight (mw), and solubility of chitosan samples extracted from shrimp wastes using microwave technique [81].

irradiation in order to reduce the impact of environmental pollution due to excessive use of chemical treatments [80–82]. The study will examine the effect of chemical addition, reaction time, operating temperature on manufacturing, and chitosan DD under microwave irradiation. These results will be compared to those from conventional heating methods to compare results. As part of this research, they developed the design and manufacture of a proton prototype for the production of chitosan from shrimp shell waste. Research has concluded that microwaves will accelerate reaction time.

The results showed that the demineralization condition of shrimp waste was achieved at the concentration of HCl 3,5 N solution with the weight ratio of shrimp shell waste and HCl solution of 1: 5 (w/v), at a temperature of 50°C during 1 h heating. In those conditions, the ash content was 8.06%. Ash content decreases to 5.4% if the demineralization reaction is carried out under microwave irradiation with 130 watts for 10 min. The optimum condition of the deproteinization process was achieved by heating at a temperature of 70°C for 2 h and at 4% NaOH concentration for shrimp waste ratio: a NaOH solution of 1:5 (w/v). In this condition, they obtained nitrogen levels of 1.882% (11.763% protein content). If the deproteinization reaction was performed under microwave irradiation with 130 W of power for 15 min, the nitrogen content obtained was 1.833% (11.461% protein content) (Table 10).
