Siltite Ferrules for GCMS interface - problems

[Dr Lou]

Hi all,

My first post here - although I use this board frequently to read threads.

I am using siltite nuts and ferrrules for the GCMS interface as I am using high oven temperatures. Using an Agilent 5975C in EI mode.

I am new to using these siltite ferrules but have just installed a new Inferno column (30 m x 0.32 mm i.d x 0.25 um film) using 0.32 mm ferrules and silitite nut.

As I pump the ms down - everything seems fine. Turn on the transfer line (280 C) and the over (40C) - still fine.

Turn the oven up to 100C - snap! The column breaks at the point where is joins with the MS interface nut. This means the MS gets very cross indeed as the vacuum is lost and shuts down.

I tried it again and the same happened.

Gone back to using a vespel/graphite ferrule and the standard Agilent nut. It is pumping down now so we will see.

Anyone had anything similar with these nuts and ferrules?

Thanks for your time,

Louisa


Edit: Forgot to say I am following the instructions for the ferrules. Tighten until the ferrrule bites the coloumn, then tighten a tiny bit more. I get an excellent air tight seal - the vaccum is 1 x 10-5 with less than 4% air in the tune.

[MSCHemist]

I use siltite's all the time on my quickswap which is at the transferline. The main trouble I've had with them are leaks specifically I had a nightmare trying to get the insert to make a tight seal with the transferline. I took weeks and I had to convince Agilent to send me a second insert because the first was defective and even then I had to use an oven mit and crank down on the sucker. I am afriad to ever take it off.

The ferules on the column I haven't had much issue with. I had one that didn't make a good seal and I had to tighten it more than usual but most are fine and I've used them on .25mm DB5, Innowax, and the Gerstell restriction tube coming from the ODP. Sounds like the polyimide coating is getting damaged when you fix the ferrule on. Perhaps your tool is faulty or the nut had a bur or something.

[Dr Lou]

Hi MSCHemist.

Thanks for your reply. Good to know they can be used successfully!

I thought that it was maybe a defect in the column or it was snagged while being placed - but I did it twice, the second time very carefully and still had the same issue.

On closer inspection of the ferrule, it looks like the column snapped inside the ferrule.

Could it be that the hole through the ferrule isn't uniform and it is narrower in the middle and even the gentle tightening I did was too much plus the heat caused the breakage?

The vespel/graphite ferrule and original nut seem to be holding . . . .

[Dr Lou]

Thought I would update this as I am still having problems.

Today I didn't even pump down the MS and just connected the column at the MS interface.

I tighten these ferrules a tiny amount each time and then I get the ferrule to bite, go to close the oven door and PING. It broke again. I can't have tightened the nut more than 25 degrees of which 20 degrees weren't actually biting the column - I could slide the column back and forth throught the transfer line.

What am I doing wrong? SGE seem to think the OD of column is the issue.

Any thoughts from anyone - I am about to assign these metal ferrules and nuts to the scrap heap!

[cleh]

What is the ID of the ferrule. A 0.32mm OD column needs a 0.5mm ID ferrule.

[Dr Lou]

The ferrules are for 320 um columns - listed as 0.5 mm on the packet.

[MSCHemist]

Yep It has been my experience too that getting a siltite ferrule to make a seal at the transferline is extremely difficult. Getting them to make a seal with the fitting has not been a problem but getting a seal on the transferline is a nightmare.

[Don_Hilton]

I use the siltite ferrules on the transfer line to a LECO Pegasus - and they work very well.

[Dr Lou]

Don_Hilton, what type of column are you using - standard capillary?

[Don_Hilton]

I'm using 0.2 ID capillary