Desalting and buffer exchange are two of the most widely used applications of gel filtration chromatography. Desalting involves the chromatographic separation of macromolecules from smaller molecules such as buffer components, salts and unreacted labeling reagents. Buffer exchange is used to switch a protein or molecule into a more appropriate buffer for applications such as electrophoresis, ion exchange, affinity chromatography or storage.

In both desalting and buffer exchange, the macromolecular components are recovered in the same buffer used to equilibrate the column. If water is used for equilibration, the components will be desalted. If another buffer is used, buffer exchange will result. Buffer exchange may be performed with each of the desalting products listed below after pre-equilibration with the desired buffer.

Read on to learn more about these products for desalting:

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Overview of Buffer Exchange

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High-Performance Dialysis and Desalting Technical Handbook

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Tech Tip (#52): Pierce Spin Cup and Column dimensions and volumes

Zeba Desalting Products

Thermo Scientific Zeba Desalting Products contain a proprietary high-performance desalting resin that offers exceptional desalting and protein-recovery characteristics compared to other commercially available resins. Even very dilute (25µg/ml) protein samples can be successfully processed to obtain greater than 95% retention (removal) of salts and other small molecules and good recovery of proteins and other macromolecules.

The Zeba Spin Desalting Columns (available in five column sizes) and two MWCOs (7K and 40K) provide an easy-to-use format that dramatically improves results over standard drip-column methodologies. This eliminates the need to wait for samples to emerge by gravity flow and monitor fractions for protein recovery. Zeba Desalting Columns require no chromatography instrumentation, cumbersome column preparation or equilibration and they can process multiple samples in ~8 minutes.

Zeba Desalting Resin also comes pre-packed in 96-well filter/centrifuge plates and in two sizes of Pierce Chromatography Cartridges.

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Zeba Spin Desalting Columns, 7K MWCO
Zeba Spin Desalting Columns, 40K MWCO
Zeba Spin Desalting Plates
Zeba Desalting Chromatography Cartridges

Polyacrylamide Desalting Columns and Spin Columns

Polyacrylamide Desalting Columns are pre-packed with porous polyacrylamide beads. The 6K MWCO columns have a wet bead diameter of 90–180µm. The 1.8K MWCO columns have a wet bead diameter of 45–90µm. These columns are ideal for separating low MW compounds with a fractionation range of 0.1–1.8K. The polyacrylamide beads are not subject to enzymatic degradation and will not serve as a nutrient for microbial growth. The resin is very hydrophilic, so hydrophobic binding to sample molecules is minimized. Polyacrylamide resins also eliminate sample contamination by low MW sugars which can occur when using crosslinked polysaccharide supports. In addition, oxidizing agents can be removed without destroying the support. This resin is susceptible to hydrolysis of amide groups under extreme pH conditions, so an operating pH of 2–10 is recommended at room temperature. The polyacrylamide resin can also be autoclaved at pH 5.5–6.5 for 30 minutes at 120°C.

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Polyacrylamide Desalting Columns
Protein Desalting Spin Columns

Excellulose Desalting Columns

Excellulose Desalting Columns are pre–packed with small, porous cellulose beads. These columns have a wet bead diameter of 100–200µm and an exclusion limit of 5K. Excellulose Resin is extremely stable to heat, freeze-thaw cycles, organic solvents and acidic or basic conditions. It also demonstrates excellent mechanical stability and offers excellent sample recoveries as a result of the slow flow rate.

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Excellulose Desalting Columns

Dextran Desalting Columns

Dextran Desalting Columns (5K MWCO) are pre-packed with crosslinked dextran. The wet bead diameter is 50–150µm. The resin has good rigidity for easy handling and excellent flow properties. The Dextran Gel is stable in water, salt solutions, organic solvents and alkaline or weakly acidic solutions. It is 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.

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Dextran Desalting Columns

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