3-channel GC for DHA and methanol analysis

[Mreza555]

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

[rb6banjo]

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.

[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

[Mreza555]

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

[Sunny.Singh]

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