Chromatography Forum

Hello all

Just started a new job on a agilent GC FID/MS. I havea couple of questions.

WE have a birdsnest in the oven as the columns from the "spliter" to the FID and MS is tangled everwhere. My question is there some special string to tie this to make it tidier? or is there other options?

The second question I have is that split to the FID and the MS seems strange. I get decent FID results but get very little through to the MS. Is the common? Is there a way to fix this?

thanks in advance for your help

M

Rocknroll99 wrote:
Hello all

Just started a new job on a agilent GC FID/MS. I havea couple of questions.

WE have a birdsnest in the oven as the columns from the "spliter" to the FID and MS is tangled everwhere. My question is there some special string to tie this to make it tidier? or is there other options?

The second question I have is that split to the FID and the MS seems strange. I get decent FID results but get very little through to the MS. Is the common? Is there a way to fix this?

thanks in advance for your help

M

1. Google for : Restek High-Temperature String
2. Not common. Restrictor capillaries (either lengths or diameters) choosen non adequately to demands. Fix is simple - change those capillaries from the splitter to detectors. But finding right parameters is not so easy.

Multiple columns and a split between MS and FID is a fancy set up, presumably for some special purpose. With luck there might be some in-house documentation that describes how to troubleshoot and adjust it.

Peter

http://www.filedropper.com/gc-mssplitcalculator

This is an excel file in which you can calculate the length of your restrictor columns for a given split between FID and MS.

If you have multiple columns just use the sum of their flow as the column flow.


I have a similar setup with a FID and a MS.

Hello,
If you question is why the decrease in MS response? as a function of using the splitter,
this can be categorised into 2 parameters.

1) Makeup Gas Dilution : typically a column running from the injection port to a MS will have a flow
rate of 1ml/min, when using the splitter, there is makeup gas added to the splitter,
this can be usually from 3ml/min as set up by an Agilent Tech, you can use the Excel sheet
supplied by Forse, so calculate the actual extra volume of make up gas supplied.
WARNING!: You can measure this effect by dropping the Aux pressure, but not too much
as the system may try and draw gas into the MS from the FID.(save the method with a new test name)

2) Fix ratio : The splitter will always split to the MS and FID in the same ratio during a temperature
programme, so by changing the lengths, you can change the ratio.
WARNING!: If you shorten the MS column, without adjusting the Aux pressure, you will increase the
Makeup Gas dilution effect, and could actually lose response even though you altered the ratio.
Use the Excel sheet to test, p.s. you need to know the column Internal Diameters, as it may be
.1mm to MS and .18 to the FID.

kind regards
Alex

Bear in mind that forse and chemstation are assuming that you have an Agilent post-column splitter. I sounds to me, since you say "columns" that you have a splitter at the inlet end of two columns - one going to the MS and one to the FID.

More details about you set-up would be useful.

Peter

Peter Apps wrote:
Bear in mind that forse and chemstation are assuming that you have an Agilent post-column splitter. I sounds to me, since you say "columns" that you have a splitter at the inlet end of two columns - one going to the MS and one to the FID.

More details about you set-up would be useful.

Peter

Presumably he names restrictor capillaries after splitter incorrectly. They are not columns, just fused silica tubing.
But let's wait for details.

thanks for all the help, I will digest it all andget back if there is more issues.

Regards

MAtt

Hi forse,

I have a similar setup and this calculator might be useful, could you resend this file, please!

Thanks

Forse wrote:
http://www.filedropper.com/gc-mssplitcalculator

This is an excel file in which you can calculate the length of your restrictor columns for a given split between FID and MS.

If you have multiple columns just use the sum of their flow as the column flow.


I have a similar setup with a FID and a MS.

Xcalibur wrote:
Hi forse,

I have a similar setup and this calculator might be useful, could you resend this file, please!

Thanks

Forse wrote:
http://www.filedropper.com/gc-mssplitcalculator

This is an excel file in which you can calculate the length of your restrictor columns for a given split between FID and MS.

If you have multiple columns just use the sum of their flow as the column flow.


I have a similar setup with a FID and a MS.

Here you go. i re-uploaded it with the same name.

http://www.filedropper.com/gc-mssplitcalculator

Forse wrote:
http://www.filedropper.com/gc-mssplitcalculator

This is an excel file in which you can calculate the length of your restrictor columns for a given split between FID and MS.

If you have multiple columns just use the sum of their flow as the column flow.


I have a similar setup with a FID and a MS.

Can you post that calculator again? Thank you!

Here you go. i re-uploaded it with the same name.

http://www.filedropper.com/gc-mssplitcalculator

Forse wrote:
Here you go. i re-uploaded it with the same name.

http://www.filedropper.com/gc-mssplitcalculator

I know this is an old thread, but any chance that excel calculator is available anywhere?

Forse wrote:
http://www.filedropper.com/gc-mssplitcalculator

This is an excel file in which you can calculate the length of your restrictor columns for a given split between FID and MS.

If you have multiple columns just use the sum of their flow as the column flow.


I have a similar setup with a FID and a MS.

Hello,
I am coming to you because I have a similar installation with a FID and a MS. We have a problem, we have to calculate the length of the restriction column to put for a distribution between FID and MS. Is it possible to give us the link to download your excel document?

Thanks,