Restek Corporation

What is the pressure limit for my LC column?

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Courtesy of Restek Corporation

This is a question we get in Tech Services fairly often.  Unfortunately, we are not able to provide a published limit for every column that we produce, but here are a few of them that we have specified:

  • For 3 and 5 um fully porous particle ROC LC columns, the maximum operating pressure is 400 Bar/ 5800 psi, which is also the limit for older or more conventional HPLC systems and close to the limit for column hardware. My personal preference is to operate below 200 Bar/ 2900 psi if possible, although the 3 um particle columns will tend be towards the upper range in terms of pressure.
  • For Raptor 2.7 um (superficially porous particle) columns, the maximum pressure rating for these columns and for many mid-pressure range HPLC instruments is 600 Bar/ 8700 psi. I would prefer to operate below 500 Bar/ 7250 psi as much as possible.
  • For Raptor 5.0 um (superficially porous particle) columns, the maximum pressure rating for these columns and for older and more traditional HPLC instruments is 400 Bar/ 5800 psi. I would prefer to operate below 300 Bar/ 4350 psi as much as possible.
  • EXP guard holder (catalog #25808) and EXP fittings that are used with Raptor columns and guard cartridges are rated up to 20,000 psi when tightened by wrench, 8,700 when hand-tightened.
  • UltraShield and Inline filters (catalog #24993), that are used with our Pinnacle DB UHPLC (1.9 µm) columns, are rated up to 1000 Bar/ 14700 psi.

The difficulty in giving an absolute pressure limit for various columns is that the expectations are different depending on the application and the column dimensions.  I usually refer customers to the table from my blog post Building up pressure on HPLC?, which was originally intended for fully porous particle columns.  Please see below for an updated version of this table. As you can see, the predicted pressure is affected by the column dimensions, flow rate and the specific solvents that are used.  Aqueous mobile phases usually produce a backpressure similar or slightly higher than what is shown here for methanol.  Please keep in mind that because backpressures typically increase over the lifetime of the column, flow conditions for a new column should be established towards the lower end of the operating range if possible.

predicted pressures LC

Although this table was intended for fully porous particle columns, the predicted pressure is not too far off from what it would be for a superficially porous column with the same particle size.  For example, the results above for 3.0 µm particle columns can be used also to give a rough estimate of pressures for a 2.7 µm Raptor SPP column.

In all cases, it is important to stress that for best chromatographic results, all LC and UHPLC columns should be used as close as possible to the optimal flow rate.  Operating close to the optimal value also helps to ensure that the pressure stays within a range appropriate for instrumentation and for the specific column hardware.

Optimal flow rates for all of our LC columns are shown here in this table from our catalog:

optimal flow rates

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