Chromatography Forum

To everybody,
What is the best way to clean 1/8'' Stainless Steel tubing grade 304 for packed column use.
Which solvent to use and what is the procedure?

thank you

dany

There isn't a 'best way', but there are many ways.

A single step or a single solvent is not suggested as a suitable means of cleaning tubing.

Some vendors even use steam as a single step however.

Cleaned tubing for refrigerants is a possibility.

Vendors such as Alltech and Supelco (and others) offer precleaned tubing.

You should have the tubing cleaned with a detergent, an alcohol, with hydrocarbon and deionized water rinses, followed by a heat treatment with a pure gas ventilation.

Depending upon application you may need to pacify the tubing. There are different means of accomplishing this.

best wishes,

Rod

Note that "refrigeration grade tubing " is often not oil free. It needs to be cleaned with a warm solvent, such as chloroform or methylene chloride.

My technique for a 50' coil is:-

Connect a 1 litre glass conical vacuum flask with a 1 hole stopper to a water aspirator vacuum system. About 50mm from one end, wrap sufficient PTFE tape ( or use a piece of silicone rubber tubing ) to seal the tubing into the stopper.
Prepare a mix of 60:40 Chloroform:methanol ( AR or HPLC grades ), and warm in hot water, and quickly suck about 100-200 ml through the tubing in 15-30 sec batches. The first couple may be slightly golden, with swarf and filings.

Then suck warm choroform or methylene chloride ( aka DCM, dichloromethane ) through, usually about 100-200 ml.
Finally, suck througn pure methanol, followed by warm nitrogen till all vapour is removed. You can use an old GC to supply the nitrogen, and warm the coil. Recap the ends.

If you need to passivate the tubing, you muct remove all organics first, then you can treat by gently sucking 1:1 nitric acid to fill, leave for about an hour, and rinse with copious amounts of Milli-Q water to pH 7, followed by a warm inert gas drying.

Passivation is really only necessary for wet or reactive samples, and it's preferable to use alternative inert tubing materials instead.

Bruce Hamilton

Bruce,

Your method should work well for you and others HOWEVER, in the USA using the technique you described (water aspirator vacuum system)might get one into a lot of trouble with the EPA (US Gov) or at least with your local safety officer.

Chloroform and DCM vapors in the lab and or entering into waste water streams is a BIG "NO NO".

The awareness of the toxicity of chlorinated solvents is growing. And the rules governing the use and release of vapors are becoming more restrictive.

While I wish sometimes I could follow your procedure it may not be possible for some of us.

Just a comment, not a criticism.

best wishes,

Rod