Chromatography Forum

What can I do do improve this chromatogram? This is a 10 ppm 1016/1260 Aroclor standard.



You can see where the 1016 begins and ends, and where 1260 starts and ends, but I'm sure you'll agree that this chromatogram could look a lot better.

I've adjusted the inlet pressure, the split flow, the split ratio, even changed the split line...

I've changed the temp program to run to a higher temperature, a longer run time...

Feel like I'm so close to getting this instrument working. It was pretty much inoperable when I acquired this in April.

Any suggestions would be greatly appreciated!

Thanks,
John

That actually looks better than some of the oily samples I've run.
It looks like a problem with resolution in that the relative peak heights are OK for that standard, I see the usual peak pairs, they just aren't resolved. As though it was an old packed column.
If this hasn't worked in its current state, are you sure that the column is all the way into the detector and the inlet? Too much dead volume would easily give you this chromatogram. Also, what is the solvent and the inlet temperature? Is the column OK or was it last used to run fish oil?

Chemwipe,

At the risk of sounding like a broken record, I would still like to see the 100 PPB shot. Can you post that?

Also, have we already discussed make-up gas? If not, we should.

Best regards.

As AICMM said a lower concentration standard would help assess column loading. You may " get more for less" . Have you tried a slower column flow?
If you are using a fid then you would want to go with make up gas.

Chemwipe,

At the risk of sounding like a broken record, I would still like to see the 100 PPB shot. Can you post that?

Best regards.

AICMM-

Sorry, I forgot that I had posted about this situation already.

I was going to run the 100 ppb standard today, but I got a

FAULT: INJA TEMP RDG

and none of the zones heated.

I did discover this, though:



Not sure if this (the exposed wires) is causing a short.

I promise I will post the 100 ppb chromatogram as soon as I get this thing running.

Thanks,
John

chemwipe,

Your discovery creates another question for me. Either you have an additional short (INJA TMP RDG) in your A injector RTD or you have a mis-wired chassis since your picture is one of your detectors. If you replace the RTD in the metal body you have the picture of and the problem goes away, then you need to start tracing your wiring to make sure that the correct RTD is reporting on the correct heater. THIS IS VERY IMPORTANT. You need to do this to prevent a thermal run away.

Best regards.

chemwipe,

Your discovery creates another question for me. Either you have an additional short (INJA TMP RDG) in your A injector RTD

Sorry, but what is the RTD and which part is it?

or you have a mis-wired chassis

And what part would be the chassis? And what would I check?

If you replace the RTD in the metal body you have the picture of and the problem goes away, then you need to start tracing your wiring to make sure that the correct RTD is reporting on the correct heater. THIS IS VERY IMPORTANT. You need to do this to prevent a thermal run away.

Best regards.

I'm guessing that the RTD is the black part that all the heated zone wires go into (not the red actuator, right?).

Thanks for the reply, I'm a little unfamiliar with some of the parts/terms.

John

Chemwipe,

Sorry. Clarifications. If you look at the detector heating block, you have the large round cartridge, the heater. If you look at the much small (0.1 inch od) ceramic cartridge, that is the RTD (the temperature sensor for the heater.) In your case (and in most cases with 5890's) the bare wire thing.

The mis-wiring would be at the black AMP connector (the small one) on the motherboard. It would suggest that the RTD that you are working on is in the wrong position on the black AMP connector (INJA instead of DETA.)

It is possible that your heaters are mis-wired as well. These are the red AMP connector you speak of that also plugs into the motherboard although further down and to the right (if memory serves correctly.)

It would be a really good idea to track the wiring from each of the heated zones (you don't have to remove anything really, you just need good light and patience) to the connectors on the motherboard to ensure that they are correct.

Best regards.

Chemwipe,

At the risk of sounding like a broken record, I would still like to see the 100 PPB shot. Can you post that?

AICMM-

Here is the 100 ppb 1254 standard:


Compare it with the 10 ppm 1254 standard: