I'm currently analyzing a drug using hplc. I've been using the same method the whole time. The flow rate has been 2ml/min and the pressure was usually around 170 bar.
The mobile phase is methanol and phosphate buffer.
I recently installed a new guard column and now the pressure has increased to 365 bar. I decreased the flow rate to 0.5ml/min, but the pressure is still high at 273 bar.
Could it be the guard column that causing this increase in pressure?
Any suggestions on how I can fix this problem?
Hi, If you changed only guard column its possibly the problem.
The new guard column is the same as the old ?
If this is not the case, the size, and particle size can increase pressure in your HPLC system.
Damola Ajani: Remove the guard column and re-test. Does the pressure drop back down to normal ? Keep it simple. If the guard column causes the pressure to increase by more than ~ 5% (depending on column dimensions and particle size), it has either been installed incorrectly, is the wrong type or something is partially obstructed (e.g. you may have clogged the system. Ex: Precip from phosphate buffer and MeOH. This may be unrelated to installation of the guard column? A few simple tests could answer this question). Do not change the flow rate to achieve a specific pressure value. HPLC does not work that way. Pressure is a measured change, not a method development variable.
If you are running isocratic, then the pressure should be stable. If you run a gradient with MeOH, then the pressure would be expected to change. For more info: Please contact someone at your school how has practical training in using your HPLC system. Someone local to you can help you troubleshoot these types of basic problems on-site with ease. Ask for help. A web forum is a poor resource in this application.
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