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- Posts: 104
- Joined: Sun Sep 13, 2015 7:54 am
My mobile phase is a gradient of Water/ACN with the following parameters
Time %Water %ACN
0.5 70 30
6.0 50 50
5.0 30 70
2.0 50 50
2.0 70 30
The problem is when the mobile phase composition becomes 70/30. This is when the pressure is at the highest (which makes sense as this combination of solvents should have the highest viscosity out of all of the ratios during the gradient). The problem is that anytime I did anything to reduce the pressure such as rinsing the system with pure organic solvents, etc... as soon as I started to equilibrate the system at that 70/30 ratio, the pressure slowly rose the entire time until it was erroring at too high of a pressure - even with no injection.
So I swapped the mobile phases to different lines - maybe something was wrong with a specific line. No fix
I removed the column still have about 250 bar of pressure. I tried to purge all the lines, but again, when I run 70/30 the pressure increases now back up to about 150bar.
It seems that the only time the pressure doesn't continually increase is if I'm at 50/50 water/ACN or lower.
The interesting thing is that even with this increase in pressure, my results at 6 months are nearly identical to those of day 0, including peak shapes and retention times. So it didn't seem to have a negative impact on the run.
I'm not very familiar with perkinelmer instruments mechanically - so I'm hesitant at the moment to start taking apart the pistons and the pump unless I have an idea for what I might need to be looking for. The instrument is a PerkinElmer Altus.
Sorry for the long post, just trying to be very detailed. Any suggestions would be great.