Chromatography Forum

Hello all,

I have recently inherited multiple problems with a HP 5890 Series II GC equipped with dual FID's. I am using this system to analyze various VOC's. One of the problems I am encountering is that column head pressure on injector B is 0. While column A is at a steady 15 PSI.Normally I would assume that there is a leak somewhere between the column and the injector. I am using the GC in split mode. I have changed the glass liner, o-ring, septum, as well as the column ferrule. I have reinstalled and rebuilt injector B (the broken one ) many times but I still cannot find the source of the leak. I have tried using soap to see if the stainless steel tubing located on the nut of injector B was cracked but have found no leaks presents. I am getting flow to the mass flow controller (I checked). But there is no pressure building up. I have even put B's (glass liner,o ring, column/ferrule) into A (the working one) to see if I installed something wrong into B ( the broken one) and they all work in A. When I cover the split vent on B the pressure does not change. Any help would be much appreciated. Thanks.

start plugging at each joint (use a sealed column nut, etc) and checking the pressures.

that and make sure that you have gas going to both injectors. they may have seperate inlets in the back. been a while since i've had to set up my 5890, but i believe you can have 2 gases going to the two different injectors.

check the back of the GC for the other gas input and make sure it's all connected correctly.

JTM,


I have checked and rechecked that the gases are in the correct place (they are). When placing a column nut to close off the column to the injector the column head pressure still reads 0. What I have noticed is that there is flow going into the solenoid valve to the split vent but it no flow can be measured coming out of the solenoid valve to the back pressure regulator. However flow does come out of the solenoid valve to a line that connects to the injector cap. Our system uses a six valve system for injection with HP DVI. No direct injection is used ever.

can you disconnect before the inlet and put a pressure gauge on it?

see if pressure is getting into the inlet at all.

Do you have flow through a column connected to B ? - if so this is a sensor problem.

Peter

I agree with Peter, You can place a flow meter at the exit of the FID, while only having a column flow. If there is no difference in the flow, it is an electrical problem. If there is a difference in flow than the column could have a leak, therefore no back pressure to the inlet. (this is assuming you are using a glass capillary column and not a packed stainless steel.

Danke,

Swap the weldments, just the weldments, on top. If the problem moves, then you have a plumbing problem in front of the inlet, if the problem stays you have a plumbing problem at or beyond the inlet.

Best regards.

Do you have flow through a column connected to B ? - if so this is a sensor problem.

Peter

this is good advice.

Yes I have flow through the column B to the detector, I uninstalled the column at the detector end and placed it in a beaker of acetone, low and behold bubble bubble bubble. I also traced the flow and am getting flow to the back pressure regulator but once it is there doesn't go out of the split vent like it should. I am wondering what the likely hood of my BPR needle valve being broken in the off position is and the likely hood of my pressure gauge is.

Thanks everyone for the help. Turns out that the the B control module (Back pressure regulator, solenoid) were all bad and had to be replaced. After replacing the control module with a new one column head pressure on B was accurately displaying the pressure.


Now to tackle the Fault Aux Temp RDG. Finding the short in the wire and replacing that. Then moving on to fix why the HP DVI/valves aren't actuating properly from EZchrom.

Good to know, thanks for the feedback.

Peter