Sample Concentration for SEC Analysis
For SEC analysis, sample concentration is
very important. The following is the pretreatment
procedure of sample.
Basically, the sample should be dissolved
in the same solvent that is to be used as
the eluent.
1) Dissolving the sample in such solvent
will make the blank peaks as small as possible.
2) In case the sample has a molecular weight of 1,000,000 minimum, soak it in
such solvent for 12 to 24 hours to let it swell. After the swelling, stir the
solvent gently for dissolution.
Strong agitation or use of an ultrasonic
bath for dissolution will degrade such sample.
3) In case the sample is a polymer, its concentration
in the solution and the injection volume
should be 0.05 to 0.5% and 50 to 100micro-L,
respectively.
If the concentration is higher, the retention
volume of the sample will increase. The optimum
concentration changes with the molecular
weight and the viscosity. The following table
gives the molecular weight vs. the optimum
concentration.
| Molecular
weight |
Sample
concentration
(W/V%) |
Injection volume
per column |
| KF-600 series |
KF-800 series |
< 5,000 |
less than 1.0 |
micro-L |
to 100 micro-L |
5,000 to 25,000 |
less than 0.5 |
25,000 to 200,000 |
less than 0.25 |
30 micro-L |
200,000 to 2,000,000 |
less than 0.1 |
> 2,000,000 |
less than 0.05 |
4) In case the sample is organic, it is desirable
that the concentration be 1% maximum and
the injection volume, 50micro-L maximum.