Cleaning glass inlet?

[Irina]

thank you very much for your posts. I think I will try to buy new ones because now I'm afraid that I will do something wrong and I will just lose time.

[Rick]

I clean my glass liner with chromic acid ( put liner in chromic acid for 1 week), than, i rinse with water and check the pH.
The final rinse is in millipore water, methanol and acetone.
After this operation, i burn my liner with a flame.
My analysis applications is Pesticides in foods

[Don_Hilton]

I would be curious as to which pesticides, the sample prep used and the technique used for flaming the liners.

[Rick]

Hello Don!
Multiresidues pesticides (450) by GC/MS. QUECHERS sample prep
No a great technique for flaming liner...simply, pass liner over propane flame.

[Don_Hilton]

Rick,
I am impressed - something to tuck away in the event I ever get to try this out. Do you hold the liner perpedicular to the flame or to you have the gasses from the flame intentionally pass into and through the liner?

[Rick]

Hi Don
I pass the liner in the flame, perpendicular to the flame AND I pass the flame in the liner too.
No need sylanization.

[Peter Apps]

Hi Rick

Interesting ! Do you flame treat after the acetone has evaporated, or do you burn the acetone off like the microbiologists do with ethanol on their inocculating loops ?

There is a lot of chemistry going on in a flame - it's by no means impossible that something good is happening to the surface silanols.

Peter

[Rick]

Flame after evaporation of acetone

[WK]

Hi Rick,
2 questions:
1) Can you store the liner indefinitely or install it immediately?
2) Do you put any wool in after the burn?
Thanks
WK

[Rick]

You can store your liner indefinitely, no problem.
You can put a glass wool after burn but i don't use glass wool because some pesticdees are retains by glass wool (organophophorous particularly)

I use single tapered liner.....with double tapered, this technique is not good.

[WK]

Hi Rick,
How concentrated is the chromic acid?
20years ago I used to soak liners in chromic acid solution
and rinse with water. And then rinse with an organic solvent.
I didn't flame them - i did soak them in an organosilane solution of some sort - but it didn't work very well - probably because I didnt use wool then.
I had primitive GCs and liners in those days so I will try with newer kit and liners. I just get such poor peak shape without wool for aldehydes.
Regards
WK

[Rick]

I use chromic acid concentrate....no dilution
After 1 week in chromic acid, rinse your liner with fresh water and check the pH....then, rinse with:
-Millipore water
-Methanol
-Acetone
and if you want, you can rinse with hexane.

After that, flame it.

Rick

[WK]

Rick,
Thanks for the info
WK

[Ron]

A lot of places no longer allow the use of the old chromic acid baths, with the health and safety issues involved.

[gcguy]

Clearly there are lots of ways of cleaning liners. I tend to clean and reuse most of mine. I build up a stock of dirty liners and do them in a batch of 20-30 at a time. Remove the wool then soak in three sets of solutions used in the following order,

Soak10%Nitric-overnight
rinse with deionised water and dry at 120oC. Repack with wool.
Soak in silating soultion-overnight
Rinse with acetone
Soak in methanol-2hours
dry and store.

The soaks can be speeded up using an untrasonic bath.