Notes on Cleaning bound Protein from RP HPLC columns

First, a few comments:

  • ·         Before proceeding with any column regeneration or cleaning procedures, always refer to the specific advice provided by the column manufacturer. Approved maintenance and cleaning instructions can often be found in the product guide which comes with the new column. Their guidelines supersede these!
  • ·         Columns are consumable items. After a suitable amount of use, the time and materials required to regenerate them may cost more than the purchase of a replacement column. Always have a new, spare column on hand.
  • ·         Protect your detector. Before washing or cleaning the column, disconnect the column outlet line and direct the column to waste only.

For RP supports, if buffers have been used, always start by washing the column down with ultra-high purity water and some organic solvent (e.g. Water/MeOH, 95%/5%) to remove all salts.

Many polymeric resins (e.g. PS-DVB) can be effectively cleaned using 0.1 M Sodium Hydroxide solution or a mobile phase solution containing equal parts of isopropanol (IPA) and 3 M Guanidine hydrochloride at ~ 50 °C. Optionally, some success has been reported using other solutions such as: 5M Urea (pH 7) buffer solution; 1 M NaCl (pH 7) and even mixtures containing some methylene chloride solvent.

For RP silica based supports, we often use a series of wash solutions. In most cases, pure water or pure organic solvents such as MeOH or ACN will not remove bound protein. An acid, base or ion pairing reagent is often needed. One of the first general wash solutions to start with is a 1% Acetic acid solution in Methanol (50/50). If desired a stronger acid such as Trifluoroacetic acid (TFA) can be swapped for the acetic acid (where possible, start with a weaker acid). This can be followed with a later solution where IPA replaces the MeOH (50/50). In both cases, adjust the pH to ~ 2.5. 5 M Urea solution has also proven effective in removing bound protein from silica supports too. Another salt solution that has shown some promise is 1 M sodium phosphate solution, pH 7.0. Run the salt solutions for about one hour at a moderate flow rate. Follow up with rinses of water and MeOH (80/20), then 90% MeOH/Water.