Comparison of UF Fractionation and Size Exclusion Chromatography SEC

The leftmost peak (lowest molecular weight, lOODa) is the salt peak which includes salts from samples and the buffer. The different figures identify an overlay of three major peaks in the NOM sample, which become more or less abundant in the different permeates. 

In assessing the effect of ionic strength it should be noted that the results of SEC analysis of the feed samples at different ionic strengths are identical. This means that any size difference which the different ionic strength may induce, is fuUy reversible once the samples are injected into the relatively strong ionic environment of the SEC analysis. 

The SEC results confirm that the concentration of organics in the permeate increases with an increase in ionic strength, in accord with the observed decrease in rejection in the UF fractionation on ionic strength increase. 

For the 10 kDa membrane the same shift is observed with the increase in ionic strength, whereas the 30 kDa membrane shows no shift (it does not retain organics at all). 

---