Pump Pressure

[yxw]

Hi, I am running an isocratic HPLC. Normally once the mobile phase is chosen, the pressure of the pump should be stable. But with my last two days HPLC running the pressure of the pump was slowly going up. For example the pressure increased from 78k gf to 88k gf within 5hours. Can anyone let me know what the problem is? Should I change guard column or anything else?
Thanks a lot!

[syx]

Higher possibility: check valve problem. See this link: http://www.lcgcmag.com/lcgc/article/art ... ?id=302242

What is your mobile phase composition?

[gbalock]

There could be a couple of things going on here. It could be a partially blocked frit. If you change out your guard column, does the pressure go down? Also is the buffer salt completely dissolved in the mobile phase? If the buffer is crashing out to some extent you could be plugging a frit.

[DR]

Or, if your samples aren't the cleanest, they will cause pressure to rise over time.

Some columns are just prone to pressure increases despite having fairly clean samples. I work with pharma. samples (not blood or urine) and have seen (for example) several varieties of Inertsil packings build back pressure over time.

[Mark Tracy]

Pressure buildup in a column tends to have a "hockey stick" profile. The more history of contamination/cleaning cycles, the faster the contamination builds up.