Chromatography Forum

i have a problem with dani GC master,(inj B pressure decreased)this is the alarm message i frequently encounter between runs and within the run ,and upon switching between pressure control and flow control of gases in methods causing the device to stop the current run and cooling the oven ,any one have an idea what causes this problem and how to solve it but in simple way because i am a beginner in using GC???

Welcome.

It is very likely that you have a leak somewhere. Check with a leak detector.

Peter

i checked leakage at the injector,post column and at the detector,No leakage,the run proceeds as usual but within the run the pressure decreases disrupting the run and then oven cooling also the same method that works effeciently in several runs in presssure control of gases when i change from pressure control of gases to flow control i got the same alarm messsage(inj B pressure decreased),sometimes after a terminating run in a sequence while the gc is cooling the oven to inject the next run also the pressure decreases

To keep the flow constant during a temperature programme the pressure has to increase, because gas viscosity increases with temperature. So you may have a leak that become significant only when the inlet pressure is high. Set the inlet pressure to whatever the maximum is during a programmed constant flow run, and check for leaks under those conditions.

Peter

Do you actually have enough head pressure at the GC to allow it to reach the higher pressure needed when you temperature program ? The GC will trip if it can't maintain the required pressure.

yes,i noticed this issue today,when i set the pressure to 10 psi ,i got the same alarm message when the program proceeded to higher temperature then when i increased the pressure to 20 psi the run proceeded to the end without a problem,but still cann't get an explain why single run in a sequence can end without a problem but during the second run the pressure drops??,thanks for help