[synthon]

I typically use columns with plastic fittings over each end, so I can remove the end and install the cotton firmly before adding silica.  Today, I've chosen to make life interesting and try something new, namely the fixed column (with stopcock). 

So, outside of using something very long to mash the cotton into place from the top of the column, does anyone have helpful tips?  I've been using a rather large piece, maybe I'll try a very small piece that might wedge itself into the bottom.

Just a curiousity.

[discodermolide]

Just mash it into place. Don't make it too tight. If it's too small it may restrict the flow.
Question: Why not buy or get your glassblower to put a sinter in the columns? It makes life much easier.

[fledarmus]

When I was packing a lot of silica gel columns, I kept a very special cotton-packing apparatus hidden in my lab so nobody would take it. It was a long piece of glass tubing with a long wooden dowel that fit inside it. Pack a small ball of cotton in the end of the glass tubing, insert it into the column until it lines up with the tube to the stopcock, and press the cotton into the tube with the wooden dowel. Voila!

[synthon]

Why not buy or get your glassblower to put a sinter in the columns?

I actually laughed out loud at this.  'My glassblower'...hilarious.  Our labware is sort of a mixed mash of 30-yr old pieces, so ordering/making new is not the norm.  I'm sure I'd be asked what was wrong with the columns we have if I asked to order a new one.  I'll keep an eye out for columns with a sinter filter in the future though.

Pack a small ball of cotton in the end of the glass tubing

That's basically what I ended up doing, using a smaller bit of cotton let it snug up nicely right above the stopcock.  By wetting it with solvent, and then taking a few short baseball like check-swings with the column, it popped right into place.  Probably best to do that last bit cautiously (and discreetly), but it worked well.

[Babcock_Hall]

Is either cotton or glass wool OK?  Is one better than the other?  Not all of our columns, particularly the small ones, have sintered glass, either.

[discodermolide]

Sorry guys, this is one of the perks of working in industry where money is no object.

[Dan]

So, outside of using something very long to mash the cotton into place from the top of the column

I do it like this. The piece of apparatus you are looking for is a "pokey stick".

[Doc Oc]

The pokey stick method works, but having exactly the right pokey stick is critical because the cotton will stick to a dowel if the end is rough.

What I've started doing is to put the stopcock in and turn it to the open position.  I'll take a cotton plug and roll it between my fingers into a football (American football) shape, then drop it in.  Then I'll apply vacuum to the stem of the column and suck the plug into place.  Works like a charm.

[fledarmus]

Is either cotton or glass wool OK?  Is one better than the other?  Not all of our columns, particularly the small ones, have sintered glass, either.

I like glass wool best, but every lab I've ever been in had boxes of cotton balls dating back to the 50s in all the unlikely corners and I would have usually needed to order the glass wool. Not that it is expensive, and you use such a tiny amount anyway, it just wasn't worth the effort of filling out all the forms when I had the cotton laying around.

Cotton does work very well for removing water from very small samples. Pack a small amount in a pipette and filter your sample through. The cellulose is quite good at removing water.

The nice thing about glass wool is that it is as unreactive as anything in your lab can very well be. Cotton unfortunately will still react with strong acids, bases, and oxidizers. Not that you are likely to be chromatographing any of those, but still...

[synthon]

Then I'll apply vacuum to the stem of the column and suck the plug into place.

Brilliant!  That's what I was looking for, vacuum.

As for cotton/glass wool, I think cotton is easier to handle, while glass wool may be more inert.

[408]

The big metal rod on the back of a vertical stand is what I use as my pokey stick.