Chemistry Reference
In-Depth Information
4.2.2.1 Solubility in Inorganic and Organic Acids
Ch is soluble in dilute inorganic acids like HCl and it dissolves in aqueous solutions
of organic acids as acetic, formic, and citric, resulting in viscous solutions [
11
].
4.2.2.2 Solubility in Organic Solvents
Ch is insoluble in organic solvent [
12
] such as THF, pyridine, petroleum ether,
trichloromethane, dichloromethane, and cyclohexane, but poorly soluble in polar
solvents like DMSO and DMF. Solubility of Ch in organic solvents increases by
introducing long chain of acyl group into Ch.
Ch is a brittle material and has the ability to absorb a quantity of moisture. Due to
the strong inter- and intramolecular H-bonding, Ch is insoluble in water, but it
dissolves in aqueous solutions of aliphatic organic acids like formic, acetic, and
citric acids. Moreover, it is soluble in some dilute inorganic acids like HCl, HI,
HNO
3
, and HCLO
4
[
11
].
Ch has, besides the hydroxyl groups, a very reactive amino group at C
2
which is
highly useful as ion exchangers [
13
] and in the preparation of a great number of Ch
derivatives [
14
]. Moreover, Ch derivatives soluble in neutral and in basic media in
addition to its aqueous acid solutions are considered as useful biomaterials [
15
], for
example, as antibacterial agents [
16
] and for drug delivery systems [
17
].
Ch is well known for its capability as a sorbent material for metal ions [
18
,
19
],
which depends on the concentration of its amino group [
20
,
21
]. Due to its
cationic properties, Ch offers good opportunities to take advantages of electron
interaction with a variety of compounds and incorporate specific properties into
the material [
22
].
4.3 Analysis of Chitosan
Analysis of Ch is carried out in order to characterize the material. Such charac-
terization includes the determination of amino groups (i.e.,
the degree of
deacetylation, DD).
4.3.1 Determination of the Amino Group Content
4.3.1.1 Acid-Base Titration Method
This method was first proposed by Broussignac [
23
], where Ch is dissolved in a
known excess amount of acid and the solution is then titrated against NaOH
