transfer line from GC column to MS

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

12 posts Page 1 of 1
Has anyone heard of using a meter or so of capillary between the end of the GC column and the inlet of the MS?
It is so annoying to have to break vacuum every time I want to put a different column on the GCMS. I'm
thinking that if there is a meter or so of capillary I could just remove the column from the capillary/gcms inlet
and quickly put a septum over it before putting on a new column.

Any thoughts?
If you put a septum over the transfer capillary you will often get a little bit of rubber in the end, so you will have to cut off the tip before you can connect the column again. In the worse case the little bit of rubber will be small enough to get sucked down the transfer line into the MS :shock: If you do want to cap the line, use a press-fit cap, I think that Restek do them.

Peter
Peter Apps
I'm actually pondering the same question today. We frequently use a guard column as the "transfer column" from the capillary to the MS. It does save us time when switching between columns for different analyses. Does it matter what size ID the columns are? If I'm using a .25mm capillary column with a .32mm transfer column, will I encounter any chromatographic problems?
wf.callahan wrote:
I'm actually pondering the same question today. We frequently use a guard column as the "transfer column" from the capillary to the MS. It does save us time when switching between columns for different analyses. Does it matter what size ID the columns are? If I'm using a .25mm capillary column with a .32mm transfer column, will I encounter any chromatographic problems?


Shouldn't be any problems, especially with larger transfer lines. I was using a metal Y connector to join two columns to a transfer line into the MS, but was having trouble getting the proper flows through the column. For that I had to use a 0.53mm transfer line with the two 0.18mm analytical columns, this allowed the end of each column to operate under vacuum instead of at an elevated pressure do to restrictions into the MS. With a single column it shouldn't matter.

The Restek adapter listed previously uses a 0.1mm transfer line to cause a restriction so that you can change a column without venting because it creates enough restriction that the flow into the MS is low when the column is removed, but I would still cool the source before using that method just in case.

I have also installed transfer lines before when I wanted the temperature of the interface to be higher than what the maximum temperature of the column phase was, to prevent the phase from bleeding into the source, that works good also.
The past is there to guide us into the future, not to dwell in.
As linked above, Restek and a few others sell "no vent" fittings for any MS that sort of rely on this principle along with a fitting that has a very tiny orifice through it combined with a really tiny capillary tube.

I was on the verge of ordering one, but then I read their tech literature on it. I wanted one for my Varian 300-TQ as at one time I was swapping columns frequently for different applications. I tend to prefer small ID columns anyway(.20 and smaller if I can get away with it) and I'd developed one particular method using a beastly 50mx.15m column. I think I was running a head pressure of around 90psi on H2 to get reasonable flow rates through it(and the...less than great...flow controllers on the 3800).

In any case, Restek's literature gives you a table to compensate for the no-vent device. IIRC, if you're running say a 20mx.18mm column, you end up telling the instrument it's something like 90m long. That's a LOT of pressure.
We use this on al our GC-MSMS systems.
I put a pre-column (no phase, same diameter) in the transferline. This way there is no bleeding of phase due to the higher temperature in the transferline.

the connection between the end of the analytical column and the transferline is made with an ultimate Union and siltite ferrules.

https://www.agilent.com/en/product/gas- ... ion-for-gc
Hello eveybody!
I would like to connect two 30mx0.25mm columns to the MS transfer line through an uncoated and deactivated restriction as well...

What diameter should have that restriction? And what about the length?
fcozzi wrote:
Hello eveybody!
I would like to connect two 30mx0.25mm columns to the MS transfer line through an uncoated and deactivated restriction as well...

What diameter should have that restriction? And what about the length?


When I did two columns into one MS I had to use a 0.53mm line into the MS and then connect the 0.25mm columns to it with a Y connector. It works well and you don't have to do anything special with column lengths in the settings to get proper flows.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
fcozzi wrote:
Hello eveybody!
I would like to connect two 30mx0.25mm columns to the MS transfer line through an uncoated and deactivated restriction as well...

What diameter should have that restriction? And what about the length?


When I did two columns into one MS I had to use a 0.53mm line into the MS and then connect the 0.25mm columns to it with a Y connector. It works well and you don't have to do anything special with column lengths in the settings to get proper flows.


How long was the 0.53 mm uncoated column into the MS?
Thank you!
fcozzi wrote:
James_Ball wrote:
fcozzi wrote:
Hello eveybody!
I would like to connect two 30mx0.25mm columns to the MS transfer line through an uncoated and deactivated restriction as well...

What diameter should have that restriction? And what about the length?


When I did two columns into one MS I had to use a 0.53mm line into the MS and then connect the 0.25mm columns to it with a Y connector. It works well and you don't have to do anything special with column lengths in the settings to get proper flows.


How long was the 0.53 mm uncoated column into the MS?
Thank you!


In my two column setup it was long enough that the splitter could sit on the floor of the oven, a gentle bend from the MS inlet and one at the bottom so the fitting was near the center of the oven.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
fcozzi wrote:
James_Ball wrote:

When I did two columns into one MS I had to use a 0.53mm line into the MS and then connect the 0.25mm columns to it with a Y connector. It works well and you don't have to do anything special with column lengths in the settings to get proper flows.


How long was the 0.53 mm uncoated column into the MS?
Thank you!


In my two column setup it was long enough that the splitter could sit on the floor of the oven, a gentle bend from the MS inlet and one at the bottom so the fitting was near the center of the oven.


Thanks!
12 posts Page 1 of 1

Who is online

In total there are 14 users online :: 0 registered, 0 hidden and 14 guests (based on users active over the past 5 minutes)
Most users ever online was 599 on Tue Sep 18, 2018 9:27 am

Users browsing this forum: No registered users and 14 guests

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry