Why is blue dextran tailing on my Ultrahydrogel 120 column? - WKB194264

ENVIRONMENT

• Ultrahydrogel
• Size exclusion chromatography (SEC)
• Gel filtration chromatography (GFC)
• Gel permeation chromatography (GPC)

ANSWER

Blue dextran is amphoteric (zritterionic)—positively charged bases can undergo cation exchange with the packing.

ADDITIONAL INFORMATION

Ultrahydrogel packing is a crosslinked hydroxylated polymethacrylate gel that has some residual carboxyl functionality.

This hydroxylation and carboxyl functionality will have a negative surface charged on this packing when the pH of the mobile phase is above the pKa of these weak acidic groups. Blue dextran's positively charged amines can be attracted to these negatively charged groups through cation exchange. When this happens, tailing is observed.

Please see the following brochure, page 24, for guidance on mobile phase choice for amphoteric analytes:

Waters Gel Permeation Chromatography (GPC) Capabilities Brochure