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- Posts: 230
- Joined: Fri Jun 22, 2012 2:51 pm
I am not very familiar with Perkin Elmer instruments. I'm trying to run headspace a Trimatrix/HS 40 connected to a Clarus 590 with an FID.
This is EPA25E. You equilibrium at a particular temp (30C is what I'm using since it's the lowest setting you can choose) and measuring the chromatogram's total area. Standards have to be butane mixed with nitrogen at various concentrations. The column runs directly from the HS40 through the heated transfer line, into the GC inlet and then to the GC detector. No guard column, no use of the GC's injection port to control pressure or anything. This setup worked fine for about a week, months ago, then experienced a dramatic drop in signal.
Perkin Elmer came out (after a loooong wait), replaced a switching valve in the HS, reinstalled everything, and got it to the point where I can run a sample and get ~10% RSD on identical samples of solvent. But that's not what I need: i need 5% RSD when I run my cal standards per the method, which is where things were before.
PE had me change the needle, the o-rings, the metal discs the o-rings sit inside of, all the fittings, etc. I also did extensive troubleshooting on the GC and FID.
I also did an experiment to rule out the FID as the problem. I cut the column near the FID and shoved both ends through the septum of a small vial. I started a run and injected gas into the vial using a gas-tight syringe. I was able to get 4.8% RSD. So I can do better with my laughable setup than the HS40 can.
Other clues: When running replicate standards of solvent, I intermittently get a second peak. I have checked using different solvents (ethanol, hexane, acetone) and see the same behavior. It's not any particular point in the run, it can be the first sample or the third, or not happen at all in a string of 3-5 samples.
Suggestions would be appreciated.
This is EPA25E. You equilibrium at a particular temp (30C is what I'm using since it's the lowest setting you can choose) and measuring the chromatogram's total area. Standards have to be butane mixed with nitrogen at various concentrations. The column runs directly from the HS40 through the heated transfer line, into the GC inlet and then to the GC detector. No guard column, no use of the GC's injection port to control pressure or anything. This setup worked fine for about a week, months ago, then experienced a dramatic drop in signal.
Perkin Elmer came out (after a loooong wait), replaced a switching valve in the HS, reinstalled everything, and got it to the point where I can run a sample and get ~10% RSD on identical samples of solvent. But that's not what I need: i need 5% RSD when I run my cal standards per the method, which is where things were before.
PE had me change the needle, the o-rings, the metal discs the o-rings sit inside of, all the fittings, etc. I also did extensive troubleshooting on the GC and FID.
I also did an experiment to rule out the FID as the problem. I cut the column near the FID and shoved both ends through the septum of a small vial. I started a run and injected gas into the vial using a gas-tight syringe. I was able to get 4.8% RSD. So I can do better with my laughable setup than the HS40 can.
Other clues: When running replicate standards of solvent, I intermittently get a second peak. I have checked using different solvents (ethanol, hexane, acetone) and see the same behavior. It's not any particular point in the run, it can be the first sample or the third, or not happen at all in a string of 3-5 samples.
Suggestions would be appreciated.
