Chromatography Forum

Witch a FID detector, methane, etane, propane, i-but, n-but, i-pro, n-pro, with column let me reach a run time lees than 90 sec ?

No.

Sorry, may first post was very poor, what I trying to say is:

We are developing a FAST GC for mud logging application,
we need reach a run time < 90sec for c1-c5 (FID detector, compositice air), with column is the propper columnfor this work ? what about with a TCD( again compositive air and the air must be separted form any Cx)

The standar equipament for mudllonging use 2-channel with OV-1 and PoraPLOT U, and reach ren times of 45sec, we like use just 1-channel.

I have done this analysis with low (less than 1000ppm each) levels in 30 seconds. The methane and ethane are 90% separated.

It is possible to perform this analysis with complete separation of C1 to C5 including neopentane in 60 seconds with FID and a backflush to vent valve or Deans switch plumbing.

I hope you can find someone to provide you the details for free.

best wishes,

Rodney George
consultant

If money is not a huge problem then

http://www.chem.agilent.com/en-US/Produ ... fault.aspx

is what we use on a regular basis to monitor CO, CO2m C1-C5, N2, and H2. We run close to 10 injections a day. Run times are close to 120sec.

Need some more detail on the application. Is it a field instrument, or is it standing in a lab? A thick film OV-1 equivalent will do the job if using a FID, you can then start at 35degC and still get seperation of C1, C2's and C3. If using a TCD a PLOT column will be needed to separate the Air and vent it.

Thank you all for yours advices,

OV-1 is the most approx solution that I have right now,
but I have some problems with it.

The oven temperature must work isothermal and
above 55°C, it is field GCs and the room temperature
may be up to 35°C, and couldn't reach good
separation form methane and ethane in run times
shorter than 100 sec

If you are using FID. Contact Restek and enquire about their 10m * 0.10mm * 0.4um Rtx-1. The phase ratio might just be enought. But injection technique is going to be critical. Any peak broading and you will have problems.

Thank you Rouan, do you believe that a valco injection valve could manege the injection successful ? what other option may I have ?

Keep in mind that separations go much faster with less viscous carrier gasses, so use hydrogen if you can. With these small molecules diffusivity is higher so you may be able to run at very high linear flow rates. In any case the optimum flow for the narrow column suggested by Rouan is a lot faster than in "conventional" diameter columns - although the very thick film might also have an effect. There is lots of discussion of optimum flows on the forum - try a search of the archives.

Peter

gamarra,

Do you really need to speciate C5's? I am currently building a mud logging GC on an Agilent chassis but the customer is grouping C5+ via backflush. The C4's are very small relative to the methane so the C5+ will be very low concentrations. For example, 80K ppm for C1 and ~40 ppm C4 in one run. That being said, C1/C4/C5+ is running in under 90 seconds. Most columns I looked at for C1 - C4 elute the C5's very late (if they have good C1/C2 separation) under isothermal conditions.

You might consider dual channels if C5's are really important to you but that means a second valve and second detector.

Best regards.

AICMM, the reason for this topic is replaced the Gc based in tow channel with one based in one channel, for mud logging application the standard analysis required is the fol owing:



Methane
Ethane
Propane
I-but
N-but
I-pen
N-pen

Remember that complete separation is not necessary to measure and ID methane and ethane accurately.

Isn't this a safety monitor? You want to know when the amounts increase, in anticipation of a blowout, right?

Why isn't 120 seconds good enough?

Do you need 90 sec? 60 sec? 30 sec? 15 sec?

What is really necessary? A reverse column step or backflush to detector configuration like AICMM mentions can be a good solution, especially if it improves the detection level for C5s (which it will).

Pay companies who do this the $5000 and it will be worth your while, no?

Best wishes,

Rodney George
consultant

Remember that complete separation is not necessary to measure and ID methane and ethane accurately.

Isn't this a safety monitor? You want to know when the amounts increase, in anticipation of a blowout, right?

Why isn't 120 seconds good enough?

Do you need 90 sec? 60 sec? 30 sec? 15 sec?

What is really necessary? A reverse column step or backflush to detector configuration like AICMM mentions can be a good solution, especially if it improves the detection level for C5s (which it will).

Pay companies who do this the $5000 and it will be worth your while, no?

Best wishes,

Rodney George
consultant

Remember that complete separation is not necessary to measure and ID methane and ethane accurately.

Isn't this a safety monitor? You want to know when the amounts increase, in anticipation of a blowout, right?

Why isn't 120 seconds good enough?

Do you need 90 sec? 60 sec? 30 sec? 15 sec?

What is really necessary? A reverse column step or backflush to detector configuration like AICMM mentions can be a good solution, especially if it improves the detection level for C5s (which it will).

Pay companies who do this the $5000 and it will be worth your while, no?

Best wishes,

Rodney George
consultant