Dear Marina,

1) Preconditioning a column with sample to saturate unspecific interaction is a well-known tool to increase SEC chromatogram stability. A colleague from our Technical Group has obtained good results by injecting 10 times the standard protein mix (which is used to generate the chromatogram in the Operating Conditions and Specifications sheet):

https://www.sigmaaldrich.com/catalog/product/fluka/69385

If this doesn't help to decrease the preconditioning time, please let me know, so that we can discuss more about your issue.

2) Regarding the analysis of blue dextran, we have 2 applications in our database in which blue dextran is injected onto G3000SW columns. The second application is without corresponding chromatogram, but you have all the working conditions to perform separation:

http://hplcapplications.tosohbioscience.com/application-database/Chromatograms/T00045?HPLC=1

http://hplcapplications.tosohbioscience.com/application-database/Chromatograms/T00052?HPLC=1

Concerning concentrations/load, concentration of 1 mg/ml and load of 100 µl should work best.

However, we recommend the analysis of dextrans on polymeric-based columns, and not on silica-based ones. For example, the TSKgel PW columns are recommended. In that case, following eluent would be suitable: buffer or salt solution with organic solvent (for example 20% CH3CN in 0.1 M NaNO3).

Moreover, depending on the reactive groups of the dextran, specific columns could be even better. For example, if the pKa of the dextran is rather low (due to the presence of specific substitution groups), we would recommend the use of TSKgel PWxl-CP columns, which have been developed specifically for the analysis of water-soluble cationic polymers.

http://www.separations.eu.tosohbioscience.com/NR/rdonlyres/2AF43838-AC61-4398-B991-ACE81A51CF83/0/F08L05A_TSKGELPWXLCP.pdf

Once again, if you want to discuss more in detail about this, please let me know!

Thank you very much, Romain