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Two cleaning procedures are recommended: A. A simple procedure for regular cleaning to prevent contamination. B. A rigourous procedure, when the column is already contaminated. A. Regular cleaning Clean the column at least every 10 - 20 separation cycles. 1. Wash with 25 ml 0.5 M NaOH at 0.5 ml/min. 2. Immediately equilibrate with at least 2 bed volumes of buffer until the UV baseline is stable. B. Rigourous cleaning to remove contamination may be required if you notice an increased back-pressure ¤ Before cleaning, make sure that the high back-pressure in the system is in fact caused by the column. Disconnect one piece of equipment at a time (starting at the fraction collector) with the pumps working. Check the pressure reading after each piece is disconnected, to determine the source of the back-pressure. (You will often find that a dirty pre-filter causes the increased back-pressure.) ¤ Check the back-pressure at the same stage during each run, since the back-pressure can vary within one run, e.g. injecting a sample and mixing different eluents may cause increased back-pressure. Also clean the column if you notice any of the following: - A space that has become visible between the adaptor and the gel bed - A color change at the top of the column and/or - A loss of resolution The following steps should be performed: 1. Change the filter at the top. (Instructions for changing the filter are supplied with the Filter kit.) ¤ Since the contaminants are introduced with the liquid flow, many of them are caught by the filter. 2. Perform cleaning with 1 M NaOH (30 min to 2 hr cycle) Rinse with water or aqueous buffer. Clean with 0.1 M HCl (30 min to 2 h cycle). Equilibrate with buffer until the baseline is stable. To remove proteins and peptides: Fill the column with 1 mg/ml pepsin in 0.1 M acetic acid and 0.5 M NaCl. Incubate overnight at room temperature, or 1 h at 37°C. Note: After enzymatic digestion, careful rinsing is required. |