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- Joined: Wed Jul 14, 2010 5:29 pm
The lab I work in has an agilent 1200 LC system hooked up to a 1956B MSD. It is generally used in walk-up mode with direct injection of samples dissolved in meoh. Some people in the lab inject more than they should, and over time this leads to steady increase in backpressure from 5-10-bar to ~60-70bar at 0.2 mL/min 50/50 water/meoh (0.1% formic acid). Many people in the lab work on extremely hydrophobic compounds, that tend to ionize poorly in apci/ES modes, hence people do large injections.
In order to resolve the backpressure issue I usually flush all of the lines with MeOH (100%) and steadly increase the flowrate until the clog is removed. Usually, the pressure will build up ~200-300bar and then it will drop back to normal. I presume this means that the insoluble material has been dissolved and is pushed to the waste can.
The source of the clog is not within the LC system. Removing the inlet to the MSD drops the backpressure. The clog is also not found in the MSD source. The pressure only increases when the solvent is directed to waste. I think there is a frit in the channel switcher thing inside the MSD that is getting clogged, as it is the last component before the waste can.
The clog is not caused by the solvent alone. If the system isn't used and is allowed to run, pressure does not increase.
I was wondering if anyone has experience using other solvent mixes to flush hydrophobic garbage out of the system. Should I use Hexane/IPA 50/50? I am guessing DCM or chloroform should be avoided.
In order to resolve the backpressure issue I usually flush all of the lines with MeOH (100%) and steadly increase the flowrate until the clog is removed. Usually, the pressure will build up ~200-300bar and then it will drop back to normal. I presume this means that the insoluble material has been dissolved and is pushed to the waste can.
The source of the clog is not within the LC system. Removing the inlet to the MSD drops the backpressure. The clog is also not found in the MSD source. The pressure only increases when the solvent is directed to waste. I think there is a frit in the channel switcher thing inside the MSD that is getting clogged, as it is the last component before the waste can.
The clog is not caused by the solvent alone. If the system isn't used and is allowed to run, pressure does not increase.
I was wondering if anyone has experience using other solvent mixes to flush hydrophobic garbage out of the system. Should I use Hexane/IPA 50/50? I am guessing DCM or chloroform should be avoided.
