GC/TCD/FID for Fixed gases

[JI2002]

I wanted to buy a GC with TCD and FID in series and a methanizer between the two detectors. My goal is to analyze nitrogen/oxygen (TCD) and carbon dioxide/methane/carbon dioxide (FID) in one run with a HayeSep D column. I need to report CO to 5 ppmv level. Does anybody have experience with such a system? Which vendor sell used/refurbished systems like this? Your suggestions and comments are greatly appreciated.

[larkl]

I'd look at using a single PDHID detector. If you can separate them, you should be able to do 5ppm easily with this detector. It is significantly more sensitive than the TCD.

We do the analysis routinely on the PLOT Carboxen 1010 column http://www.sigmaaldrich.com/catalog/Pro ... KEY&F=SPEC, but we don't get baseline resolution of the N2/O2. It's not an issue for us.


You can buy the PDHID directly from Valco and install it yourself. http://www.vici.com/support/manuals/d2.pdf

I'm afraid that I don't know of anyone that'll do it in a refurb. Someone like Wasson-ECE could build you a new one.

[willnatalie]

ook into the SRI instruments if all you need to do is simple work. They have one already configured and pretty good. I have two.

http://www.srigc.com/2005catalog/cat03.htm

Multiple Gas Analyzer #1 GC is a good choice.

outside of that I would look into companies that make a micro-GC


good luck.

[JI2002]

Thank you very much for your replies.

larkl: Can you separate CO from O2 by PLOT Carboxen 1010? I'll run ambient air samples on the system. My concern is that O2 interferes with CO with HID.

willnatalie: The system from SRI is very interesting. I'll look into it.

[DSP007]

First, perhaps you still are analyzing the carbon monoxide (CO) in the FID
Secondary
It all depends on the gas chromatograph your scheme
There are several options.
1) Two injector, 2 detectors. Sequence analysis.
Set up two columns, each to their detector.
2) One injector, two detectors. Sequence analysis.
After the column set tap with three strokes that choosing the right detector. As an option, toggle the column.
3) One injector, two detectors. Analysis of parallel. Set after the column Y and a glass tube with capillary gas stream to breed two detectors.
This work is a creative ... need to choose the length of capillaries that gas flows have been optimal.

[CE Instruments]

This is a routine system for Bruker (was Varian). Not sure about the separation on Haysep D. I have heard about the Carboxophen column but O2/N2/Ar is a bit tough on anything other than a Molsieve. I had also heard issues with Carbon type phases suffering from adsorption of gases at low ppm levels ?
TCD will not detect single figure ppm gases you need a Helium Ionisation detector.
Looking at gases in the low ppm levels you will need to use purged gas sampling valves to avoid contamination from the surrounding air. Second hand systems may be available but I would be wary of any company that has no experience of supplying and supporting such systems.

You seem to imply that you will be looking in Air , 80% Nitrogen ! and plenty of Oxygen. You should provide full details of your application to vendors. TCD is much cheaper and if the ppm levels of gases are for those detected by FID you may not need the HID

Now with Bruker

[chromatographer1]

JI2002 wrote:

"I wanted to buy a GC with TCD and FID in series and a methanizer between the two detectors.

My goal is to analyze nitrogen/oxygen (TCD) and carbon dioxide/methane/carbon dioxide (FID) in one run with a HayeSep D column.

I need to report CO to 5 ppmv level.

Does anybody have experience with such a system? Which vendor sell used/refurbished systems like this?"

I assume you meant to say carbon monoxide/methane/CO2.

To reach 5 ppm CO by TCD required an excessive amount of sample on column which won't work your separations.

Don't try carbon columns for low trace amounts of O2 or CO or CO2.

After a dual injection (two sample loops) I would use a 2 meter 1mm ID Q or D column to separate % levels of CO2 from N2/O2/CO/methane to the TCD. Use helium or hydrogen carrier Expect to service the TCD at regular intervals due to the hydrogen carrier unless you use a thermistor type TCD (not a hot wire).

Send the second injection onto a 2.5 meter 1mm ID MS5A column and a methanizer/FID. Hydrogen carrier and a methanizer are required. Expect to service the MS5A column regularly for removal of trapped CO2 and water unless you install a backflush valve with a Q or D column to backflush the CO2/water.

O2 can also be lost at low trace levels if you have not prepared your MS5A column properly.

You can do the analysis with Helium carrier if you use a HID instead of a methanizer/FID.

A dual injection will allow you to size your sample loops accordingly to the composition of the gases.

I assume you are injecting ambient air samples and are using an isothermal column oven.

Wasson and Agilent may sell systems that will do this analysis. Process analyzer companies (ABB and Siemens AA) will also sell propietary GCs for this purpose. Expect to pay >$40,000. You might find a cheaper price. See Valco for their unit.

best wishes,

Rod

[AICMM]

JI2002,

The detectors you use depend on the levels you want to work at and the components you want to look at. If hydrocarbons are not on the plate and high levels and low levels are, then a TCD and HID (mine or Valco's) will be able to cover the ranges you are interested in. Low levels (5ppm 'ish) are best done by HID since they have the appropriate sensitivity. But HID's have a more limited linear range than the TCD does. If you are looking for hydrocarbons as well, an FID might be a more appropriate complement to the HID. This was the system I worked on to measure pyrolysis gases and it worked quite well.

I build re-furbished systems with the DBD and other detectors if you care to contact me (aicmm at flash.net)

Best regards,

AICMM

[JI2002]

Thanks for the replies. Chromatographer1 is correct; I meant to say CO/CH4/CO2. I apologize for the typo.

By reading your posts and checking out the websites from some manufactures, I know I need either TCD/HID or TCD/methanizer/FID. I like the TCD/HID option, but if I need to run method 25 on the instrument, then I have to go with TCD/methanizer/FID.

I'm looking at some options and report back my experience later.

AICMM, I appreciate your expertise, I have your email in file if I need to contact you.

[chromatographer1]

JI2002

I wish to apologize to Matthew (AICMM) for leaving him off my listing of GC hardware suppliers.

I did not remember that he would sell re-furbished systems.

Be careful concerning the catalyst you use for the mathanizer, if you might send hydrocarbons, especially alkenes, through it on a regular basis. Coking up a methanizer happens often as folks forget about it.

Good luck in your work,

Rod