154 Marine Macro- and Microalgae: An Overview
Vibrational spectroscopy
In order to identify the seaweed carrageenan, agar, and alginate nature, vibrational spectroscopy can
reveal detailed information concerning the properties and structure of materials at a molecular level. Until
now, this type of analysis required the extraction of colloids, through lengthy and complicated procedures.
With the development of FTIR diffuse-reflectance spectroscopy (DRIFTS), it became possible to directly
analyze ground, dried seaweed material (Chopin and Whalen 1993).
Recently Pereira and coworkers (2003, 2009a,b) developed an analysis technique based on
FTIR-ATR (attenuated total reflectance) and FT-Raman spectroscopy, which allowed for the accurate
identification of diverse phycocolloids (see Tables 3 and 4).
Table 3. Identification of carrageenan types by infrared spectroscopy (adapted from Pereira 2006; Pereira et al. 2009a).
Wavenumbers
(cm
–1
)
Bond(s)/Group(s)
Letter
Code
Type of carrageenan
Kappa
(k)
Mu
(m)
Iota
(i)
Nu
(n)
Beta
(b)
Theta
(q)
Lambda
(l)
Xi
(x)
1240–1260
S=O of sulphate esters
+
++
++ +++
-
++
+++
++
1070
C-O of 3,6-anhydrogalactose
DA
+
-
+
-
+
+
-
-
970–975
Galactose
G/D
+
s
+
s
+
+
-
-
930
C-O of 3,6-anhydrogalactose
DA
+
-
+
-
+
+
-
-
905
C-O-SO3 on C2 of
3,6-anhydrogalactose
DA2S
-
-
+
-
-
+
-
-
890–900
Unsulphated β-D-galactose
G/D
-
-
-
-
+
-
-
-
867
C-O-SO3 on C6 of galactose G/D6S
-
+
-
+
-
-
+
-
845
C-O-SO3 on C4 of galactose
G4S
+
+
+
+
-
-
-
-
825–830
C-O-SO3 on C2 of galactose G/D2S
-
-
-
+
-
+
+
n
815–820
C-O-SO3 on C6 of galactose G/D6S
-
+
-
+
-
-
+
-
805
C-O-SO3 on C2 of
3,6-anhydrogalactose
DA2S
-
-
+
-
-
+
-
-
-, absent; +, medium; ++, strong; +++, very strong; s, shoulder peak; n, narrow peak.
Table 4. Identification of carrageenan types by Raman spectroscopy (adapted from Pereira 2006; Pereira et al. 2009a).
Wavenumbers (cm
–1
) Bond(s)/Group(s)
Letter
code
Type of carrageenan
Kappa
(k)
Mu
(m)
Iota
(i)
Nu
(n)
Beta
(b)
Theta
(q)
Lambda
(l)
Xi
(x)
1240–1260
S=O of sulphate esters
++
++ ++ +++
-
++
++
++
1075–1085
C-O of 3,6-anydrogalactose
DA
+++
-
+++
-
+
+
-
-
970–975
Galactose
G/D
+
+
s
s
+
+
-
-
925–935
C-O of 3,6-anydrogalactose
DA
+
-
+
-
+
+
-
-
905–907
C-O-SO 4 on C 2 of
3,6-anydrogalactose
DA2S
-
-
+
-
-
+
+
+
890–900
Un-sulphated b-D-galactose
G/D
-
-
-
-
+
-
-
-
867–871
C-O-SO 4 on C 6 of galactose G/D6S
-
s
-
+
-
-
+
-
845–850
C-O-SO 4 on C 4 of galactose
G4S
++
+
++
+
-
-
-
+
825–830
C-O-SO 4 on C 2 of galactose G/D2S
-
-
-
+
-
+
+
-
815–825
C-O-SO 4 on C 6 of galactose G/D6S
-
s
-
s
-
-
+
+
804–808
C-O-SO 4 on C 2 of
3,6-anhydrogalactose
DA2S
-
-
++
-
-
+
-
-
-, absent; +, medium; ++, strong; +++, very strong; s, shoulder peak.
Vibrational spectroscopy
In order to identify the seaweed carrageenan, agar, and alginate nature, vibrational spectroscopy can
reveal detailed information concerning the properties and structure of materials at a molecular level. Until
now, this type of analysis required the extraction of colloids, through lengthy and complicated procedures.
With the development of FTIR diffuse-reflectance spectroscopy (DRIFTS), it became possible to directly
analyze ground, dried seaweed material (Chopin and Whalen 1993).
Recently Pereira and coworkers (2003, 2009a,b) developed an analysis technique based on
FTIR-ATR (attenuated total reflectance) and FT-Raman spectroscopy, which allowed for the accurate
identification of diverse phycocolloids (see Tables 3 and 4).
Table 3. Identification of carrageenan types by infrared spectroscopy (adapted from Pereira 2006; Pereira et al. 2009a).
Wavenumbers
(cm
–1
)
Bond(s)/Group(s)
Letter
Code
Type of carrageenan
Kappa
(k)
Mu
(m)
Iota
(i)
Nu
(n)
Beta
(b)
Theta
(q)
Lambda
(l)
Xi
(x)
1240–1260
S=O of sulphate esters
+
++
++ +++
-
++
+++
++
1070
C-O of 3,6-anhydrogalactose
DA
+
-
+
-
+
+
-
-
970–975
Galactose
G/D
+
s
+
s
+
+
-
-
930
C-O of 3,6-anhydrogalactose
DA
+
-
+
-
+
+
-
-
905
C-O-SO3 on C2 of
3,6-anhydrogalactose
DA2S
-
-
+
-
-
+
-
-
890–900
Unsulphated β-D-galactose
G/D
-
-
-
-
+
-
-
-
867
C-O-SO3 on C6 of galactose G/D6S
-
+
-
+
-
-
+
-
845
C-O-SO3 on C4 of galactose
G4S
+
+
+
+
-
-
-
-
825–830
C-O-SO3 on C2 of galactose G/D2S
-
-
-
+
-
+
+
n
815–820
C-O-SO3 on C6 of galactose G/D6S
-
+
-
+
-
-
+
-
805
C-O-SO3 on C2 of
3,6-anhydrogalactose
DA2S
-
-
+
-
-
+
-
-
-, absent; +, medium; ++, strong; +++, very strong; s, shoulder peak; n, narrow peak.
Table 4. Identification of carrageenan types by Raman spectroscopy (adapted from Pereira 2006; Pereira et al. 2009a).
Wavenumbers (cm
–1
) Bond(s)/Group(s)
Letter
code
Type of carrageenan
Kappa
(k)
Mu
(m)
Iota
(i)
Nu
(n)
Beta
(b)
Theta
(q)
Lambda
(l)
Xi
(x)
1240–1260
S=O of sulphate esters
++
++ ++ +++
-
++
++
++
1075–1085
C-O of 3,6-anydrogalactose
DA
+++
-
+++
-
+
+
-
-
970–975
Galactose
G/D
+
+
s
s
+
+
-
-
925–935
C-O of 3,6-anydrogalactose
DA
+
-
+
-
+
+
-
-
905–907
C-O-SO 4 on C 2 of
3,6-anydrogalactose
DA2S
-
-
+
-
-
+
+
+
890–900
Un-sulphated b-D-galactose
G/D
-
-
-
-
+
-
-
-
867–871
C-O-SO 4 on C 6 of galactose G/D6S
-
s
-
+
-
-
+
-
845–850
C-O-SO 4 on C 4 of galactose
G4S
++
+
++
+
-
-
-
+
825–830
C-O-SO 4 on C 2 of galactose G/D2S
-
-
-
+
-
+
+
-
815–825
C-O-SO 4 on C 6 of galactose G/D6S
-
s
-
s
-
-
+
+
804–808
C-O-SO 4 on C 2 of
3,6-anhydrogalactose
DA2S
-
-
++
-
-
+
-
-
-, absent; +, medium; ++, strong; +++, very strong; s, shoulder peak.