Anion Exchange Column

• Bio-Scale™ Mini UNOsphere™ Q Anion Exchange Columns

  

  Choose these cartridges for high binding capacity — up to 180 mg/ml of BSA — with low backpressure. Use with medium- or high-pressure systems for initial capture steps.

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• Bio-Scale™ Mini Macro-Prep^® High Q Anion Exchange Columns

  

  These durable, double-wall cartridges feature high-capacity macroporous media with strong or weak functional groups. Use with medium- or high-pressure systems for initial capture steps.

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• ENrich™ High-Resolution Anion Exchange Columns

  

  Use these high-resolution anion exchange columns to achieve reproducible separation of biomolecules at fast flow rates. Use with medium- or high-pressure systems for final polishing steps.

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• UNO^® Monolith Anion Exchange Columns

  

  These anion exchange columns have a nonporous continuous bed matrix for fast mass transfer, excellent resolution and high capacity. Use with medium- or high-pressure systems for final polishing steps.

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Anion Exchange Column Design

Ion exchange chromatography is used to separate charged molecules. In an anion exchange column, the packing is positively charged and therefore retains negatively charged molecules by coulombic interaction. The bound molecules are eluted with an anion gradient. For molecules with multiple charged groups, such as proteins, it is the overall charge in a given buffer chemistry (pH, etc.) that determines whether and how strongly the molecule will bind to the column stationary phase.

Anion exchange chromatography columns are available with matrices having either strong or weak functional groups. The strong anion exchange matrix is quaternary ammonium, and is designated Q. The weak anion exchange matrix is diethylaminoethyl, or DEAE. An intermediate strength resin, which contains primarily tertiary with some quaternary amines, is also available.

The pH of the buffer in the column determines the charge of each of the constituents in a sample. The charge of strong anion exchange resins is minimally altered by a change in pH and can operate over a broad pH range. DEAE is more affected by changes in pH, with a usual operating range of pH 7–10.

The availability of a wider working pH range with strong anion exchange columns provides the ability to use pH to change the net charge of the target molecules to make them bind more strongly, more weakly, or not at all. Chromatography may be carried out in positive mode, where the target(s) of interest bind strongly to the column and (many) other molecules do not bind as strongly. Negative mode is common in polishing, where contaminants bind to the anion exchange column and the target molecule does not bind and is thus not retained on the column.

Elution is usually achieved with a salt gradient. The most common ions are PO₄^3–, SO₄^2–, COO^–, and Cl^–. Choice of anion depends on the desired elution profile and which ions are compatible with future purification or future use of the analyte(s).