Chromatography Forum

Hi
there is a 3channel gc inquiry:
- channel 1 : DHA analyzer (ASTM D6730) , S/SL injector ,FID, liquid sampling valve (LSV) , WCOT column
- channel 2 : FID with Dean's switching valve(impurities in methanol), S/SL injector, WAXMS column
- channel 3 : NPD, S/SL injector, WAXMS column.

For 1st channel we have separate injector, column and detector. do we need a LSV here?
For 2nd & 3rd channel there is one injector,2 columns and 2 detectors. is it necessary to have a Deans switching valve?

Does anyone know the approximate detection limits for these 3 channels?

any further suggestion would be appreciated.

thanks

It looks like a complicated system. If the second column is a wax for both analyses (FID and NPD), you could just have 1 column coming out of second inlet, run it into the switch, and toggle between the FID and NPD. There's no issue when connecting 2 detectors that are at essentially the same pressure. This configuration would give you the maximum sensitivity. This is what I would do if I were you. This means you'd have to analyze the sample twice to get all of the flame and nitrogen/phosphorus data.

I am running in this mode on one of my systems. Inlet to column to Dean's switch and I toggle between a mass spec and an SCD (both under vacuum). The same lengths of coated fused silica were used to connect the switch to the detectors. I have to analyze my samples twice if I want all of the MS and SCD data. Not splitting the effluent at the injector to go to 2 columns gives me maximum sensitivity for both detectors.

I don't know anything about D6730 so I can't address the LSV question.

You are analyzing methanol for impurities or methanol as an impurity?

Detection limit is a direct function of split ratio - so.... hard to say without more information.

What is the idea behind the LSV here?

Best regards,

AICMM

You are analyzing methanol for impurities or methanol as an impurity?

Detection limit is a direct function of split ratio - so.... hard to say without more information.

What is the idea behind the LSV here?

Best regards,

AICMM

Hi
we analyze impurities in methanol. and as a detection limit, i just wanted to know a rough amount for these typical analysis.
LSV has been suggested for condensed and cylinder samples that it could be easier to inject.
Regards
MReza

Hi I am interested in understanding the set up that you have in detail. Could you please reach out at sunny.singh@scioninstruments.com