Applications
• Removing salts from protein solutions
• Eliminating phenol from nucleic acid preparations
• Separating excess crosslinker from conjugate preparations
• Removing excess derivatizing agents from modified proteins
• Withdrawing unreacted dye from fluorescent antibodies
• Eliminating free radiolabel from labeled proteins
• Buffer exchange

Gravity-flow gel filtration using dextran desalting columns
Gravity-flow gel filtration involves the chromatographic separation of molecules of different dimensions based on their relative abilities to penetrate a suitable stationary phase. A chromatographic matrix, usually consisting of very small, uncharged porous particles in an aqueous solution, is packed into a column and then used for separation via size exclusion. Different levels of separation can be achieved based on the pore size of the medium packed into the desalting column—in our case, dextran. With size exclusion filtration, large molecules are excluded from the internal pores of the gel and emerge from the column first. Smaller molecules can penetrate the pores, then progress through the column at a slower rate. These smaller molecules are subsequently flushed through the column with additional buffer volume. Our Dextran Desalting Columns are rigid for easy handling and provide excellent flow properties. Dextran is stable in water, salt solutions, organic solvents and alkaline or weakly acidic solutions. Dextran is also heat-stable and can be autoclaved dry or in solution at a neutral pH for 30 minutes at 120°C without affecting its chromatographic properties.