1070-4272/04/7703-0484C2004 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 77, No. 3, 2004, pp. 484! 487. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 3,
2004, pp. 490! 493.
Original Russian Text Copyright + 2004 by Novikov.
AND POLYMERIC MATERIALS
Acid Hydrolysis of Chitin and Chitosan
V. Yu. Novikov
Knipovich Arctic Research Institute of Fishery and Oceanography, Murmansk, Russia
Received December 17, 2002; in final form, January 2004
Abstract-Acid hydrolysis of chitin and chitosan recovered from shells of sea Crustacea was studied by
exclusion high-performance liquid chromatography.
Antiarthrosis preparations based on chitin oligo-
mers and glucosamine salts attract growing attention
[1, 2]. The yield and quality of glucosamine hydro-
chloride produced from chitin
depend in a complex
manner on the chitin properties . To understand this
dependence, the mechanism of acid hydrolysis of
chitin was studied in more detail.
Acid hydrolysis of chitin (CTN) and chitosan
(CSN) was examined in . The aim of this work
was to determine the limiting degree of chitosan
deacetylation suitable for preparing glucosamine. For
this purpose, the influence of the degree of chitosan
deacetylation on its acid hydrolysis was studied by
exclusion high-performance liquid chromatography
We used CTN prepared by deproteinization and
demineralization of shell of North shrimp (Pandalus
borealis) by the procedure in . The chitosan content
in the sample was 97 wt %; the ash content was lower
than 0.1 %; the particle size was no larger than 2 mm.
The chitosan samples were prepared by deacetyla-
tion of CTN and CSN. Chitosan with the 68.0%
degree of deacetylation (DD) (CSN-1) was obtained
by treatment of CTN with 50% aqueous NaOH at
95+ 5oC for 30 min. The samples with DD of 88.0
(CSN-2) and 92.0% (CTN-3) were prepared under
similar conditions from CSN-1 and CSN-2, respec-
Chitin and chitosan were hydrolyzed with 36.5%
HCl at 50 and 70oC. The resulting hydrolyzates were
diluted with distilled water, neutralized to pH 3, and
Ekobiotek-Murmansk Research and Technical Center, Limited
filtered through a glass filter with pore diameter of no
more than 10 mm (POR 10).
The degree of CSN deacetylation was determined
by potentiometric titration of a 2% CSN solution with
0.1 M HCl by the procedure in . The absolute
error of the determination was 0.5%.
The hydrolysis products of CTN and CSN were
separated by HPLC on an LC10A
(Shimadzu, Japan) with TSK-gel Alpha-2500 (30 0
0.78 cm) column and TSK-guardcolumn Alpha (6 0
0.4 cm) precolumn (TOSOH, Japan). The hydrolyzate
samples were applied in the form of 0.1% solutions in
the eluent (0.3 M NaCl acidified with HCl to pH 3).
The hydrolysis products were detected by the absorp-
tion at 210 nm.
The UV detection of the hydrolysis products al-
lowed us to monitor changes in the concentration of
acetylated compounds and acetic acid. The consider-
ably weaker absorption of deacetylated CSN oligo-
mers and D-glucosamine (GA) was obscured by the
strong band of the acetylated products. Monomeric
N-acetylated glucosamine (AcGA) was identified by
comparing its retention time (9.78 min) with that of
pure GA (9.86 min). For this purpose, a 5% GA solu-
tion in the eluent was used.
Based on the published chromatographic data on
CTN oligomers , we assigned the other chro-
matographic peaks to the acetylated oligomers (Fig. 1).
If peak 2 is due to AcGA, then peaks 3 and 4 are
assigned to N,N`-diacetylchitobiose and N,N`,N"-tri-
acetylchitotriose, respectively. The semilog plot of the
molecular weight (MW) of these compounds on the
elution time t is linear. The nonlinear deviation for
GA can be due to either characteristics of the linearity
the column or structural difference of the deacetylated
monomer from AcGA. Hence, GA cannot be used to
construct the calibration curve.