Handbook of Size Exclusion Chromatography and Related ...

Table 10 Refractive Index Increment (dn/dc) of Cellulose Used for the Evaluation of
SEC by On-Line Laser Light-Scattering Detectors a
Sample Solvent
The accuracy of the obtained M w value presupposes that the dn/dc has been
properly determined under the conditions used for the SEC. Sample solutions
should preferably be dialyzed against pure solvent prior to determination, but this
is not possible for LiCl/DMAc solutions because the solvent will swell or dissolve
the dialysis membranes. It is important to prepare the solvent in a reproducible way
because an increase in the concentration of LiCl decreases the dn/dc value (222).
In Table 10, reported dn/dc values of some types of celluloses used for evaluation
of chromatograms by on-line light-scattering detectors are shown.
7 CONCLUSIONS
dn/dc
(mL/g)
Wavelength
(nm)
Temperature
(8C) References
CTC THF 0.163 632.8 — 231
CTC THF 0.155 633 25 121
CTC THF 0.163 690 Ambient 117
TMSC THF 0.059 646 25 101
CMC 0.02 M or
0.1 M
0.163 633 25 156
NaNO3
Cellulose ethers b
0.01 M NaCl 0.128–0.132 632.8 30 224
Cellulose ethers b
Phosphate buffer
I ¼ 0.1, pH 6.5
0.15 632.18 — 165
Cellulose 0.5% LiCl/
DMAc
0.163 690 — 194
Cellulose 0.5% LiCl/
DMAc
0.104 633 40 198
Cellulose 0.5% LiCl/
DMAc
0.108 488 Ambient 225
a The literature reference contains dn/dc values of different types of carbanilates.
b Nonionic.
The great number of applications shows that SEC is the preferred technique to gain
information about cellulose and its derivatives. During the past decade, SEC of
cellulose has been focused on carbanilated cellulose samples or direct dissolution
of cellulose samples in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc).
For derivatives, the trend is to perform derivatization of cellulose in homogeneous
phase using LiCl/DMAc. Qualified evaluation of SEC results has
become possible by using dual detection including differential viscometry (DV)/
© 2004 by Marcel Dekker, Inc.