How to perform a solvent changeover procedure on Waters Styragel columns to convert from THF to DMF - WKB197282

OBJECTIVE or GOAL

Convert Styragel columns packed in tetrahydrofuran (THF) to dimethylformamide (DMF).

ENVIRONMENT

• Gel permeation chromatography (GPC)
• Styragel columns
• Solvent changeover

PROCEDURE

1. Set the column oven to 50 °C.  Allow the column(s) in THF to come up to temperature at a slow flow rate prior to DMF solvent introduction. (After two hours, raise the column oven to 55 ^oC and start the solvent changeover to DMF. After another 2 hours, raise the column oven temperature to 60 ^oC (see step 4 once in 100% DMF).
2. For 7.8 x 300 mm columns, set the pump flow rate to 0.1 mL/min throughout this procedure. For 6.0 x 150 mm columns, use 0.06 mL/min throughout this procedure. For 4.6 x 300 mm columns, use 0.03 mL/min throughout this procedure.
3. If you are running a gradient, program a 95:5 THF/DMF to 100% DMF over four hours.
   • If you are running in isocratic mode, make separate THF:DMF solutions in 5% steps from 95:5 THF/DMF to 100% DMF, and increase DMF strength over four hours.
4. Flush with 100% DMF for six hours per column. 
   • If there are two columns in the column bank, flush for a total of twelve hours. 
   • This equates to 10 column volumes per column.
5. This solvent switch should only be performed once in the column's lifetime.

ADDITIONAL INFORMATION

For traditional GPC columns, the risk of column damage increases when the columns are older and have been previously used for a long time, and/or when the columns have been exposed to multiple solvent switches.

GPC Columns –  General Operating Procedures when not performing solvent switch:

• Always ramp from 0.1 mL/min to approximately 1 mL/min over five minutes, for 7.8 x 300 mm columns, for example.
• Do likewise when ramping down flow rate.
• Typical operating flow rates when performing GPC separations on Styragel columns:
  • 7.8 x 300 mm columns  -  1.0 mL/min
  • 6.0 x 150 mm columns  -  0.6 mL/min
  • 4.6 x 300 mm columns  -  0.3 mL/min
• When the column is not in use but is kept on a system, keep the flow rate at 0.1 mL/min minimum at all times. Do not power-off the pump.