(Each issue we will print some of the questions we receive in our Technical Services Group. Feel free to email us your question and be and check out our extensive FAQ pages.

Question:  “What are the advantages and disadvantages when including additives to my mobile phase for SEC?”

Answer:     Additives may be used in the mobile phase as long as they are less than 1% of the total concentration.  Common additives include SDS, urea or guanidine.  They only should be considered in cases where hydrophobic interaction is suspected between the sample and column matrix and where the addition of another buffer or water soluble organic solvent is not effective.

The performance of an SEC column is irreversibly modified when the column is subjected to most additives.  This is a major disadvantage.  For example, the retention time of a sample may shift and the calculated resolution between two peaks may change compared to a column run without additives.  Furthermore, it is almost impossible to completely remove the additive from the column. Therefore, the column must be designated for use only with additives in the mobile phase for its entire lifetime.

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