corrosive solvents; exploding vials.

[matthew]

Hi,

In the vein of high throughput (acquire cancer) work, I'm toying around with some dispersive LLE methods to see if I can optimize an extraction. I am using acetone as my dispersive solvent, and tetrachloroethylene as my extractant. The aqueous solvent is amended with formic acid (to 0.1%) before I add the organic.

I admittedly have a hokey centrifuge aparatus for my 20ml scintillation vials: I have a bunch of foam that I've shoved into a plate holder for my beckman j-25 centrifuge. I'm hoping to confirm that my method works before machining up a vial holder for the centrifuge.

My problem is, errr, 2 out of the last 40 vials have exploded, which gives me concern considering I have roughly 40ul of perc in the vials (gone are the days where post-docs tricked me into doing 1L DCM extractions sans safetyware).

Not to be completely obtuse, but I'm a wannabe plant biologist, and I'm not entirely sure that I understand why my vials have exploded. Is it the formic acid? Is it just the volatility of the solvents (e.g. I should burp my vials before centrifuging)? It isn't just flawed glass; both of the lids for the vials were also destroyed.

[Bruce Hamilton]

It's probably your vials. They are unlikley to be centrifuge rated. You might get away with it if the RCF is low, AND the vial is well supported. You haven't said the vials are glass, I'm assuming they are.

If they are polymer, then it's your solvents and the RCF. The small amount of perc is unlikely to generate much HCl in the timeframe of your experiments, but may be an issue for longer storage.

Use suitable centrifugeware, and you might even find a suitable holder lying around near your centrifuge.

Please keep having fun,

Bruce Hamilton

[Pragmatist3]

Hi,

In the vein of high throughput (acquire cancer) work, I'm toying around with some dispersive LLE methods to see if I can optimize an extraction. I am using acetone as my dispersive solvent, and tetrachloroethylene as my extractant. The aqueous solvent is amended with formic acid (to 0.1%) before I add the organic.

I admittedly have a hokey centrifuge aparatus for my 20ml scintillation vials: I have a bunch of foam that I've shoved into a plate holder for my beckman j-25 centrifuge. I'm hoping to confirm that my method works before machining up a vial holder for the centrifuge.

My problem is, errr, 2 out of the last 40 vials have exploded, which gives me concern considering I have roughly 40ul of perc in the vials (gone are the days where post-docs tricked me into doing 1L DCM extractions sans safetyware).

Not to be completely obtuse, but I'm a wannabe plant biologist, and I'm not entirely sure that I understand why my vials have exploded. Is it the formic acid? Is it just the volatility of the solvents (e.g. I should burp my vials before centrifuging)? It isn't just flawed glass; both of the lids for the vials were also destroyed.

I don't believe your solvent combination is causing the failure. The aqueous/tetrachloroethelene mixture may cause some gassing but I would not expect enough to explode. You could cap and shake them manually a few seconds, crack the lid and retighten them prior to centrifugation to be sure. Scintillation vials are pretty cheap glass and not really designed for centrifugation. Spin them at lower rpm or find a different vessel for this step in the method. I will assume your foam holder is safe and that you know how important your placement and balance is in the centrifuge. Like my co-worker always reminds me: centrifuges and autoclaves cause more lab related deaths than any other piece of equipment in a lab (don't know if it's true but thats what he says).

I would make sure your vessels are capable of withstanding the force you you intend to put on them and it sounds like 2 of the last 40 weren't.

[matthew]

Hi Bruce, Pragmatist,

Thanks for the help. The vials are Kimble glass scintillation vials (borosilicate).

The foam support is a bit hokey, and I concede that the vials may have been moving a bit in the centrifuge (I squeezed the vials in between a few cyllindricial foam tubes that I wedged into a swing-out rotor's plate-holder). However, I'm a bit shocked that the two lids (caps) also broke. I'll spin a bunch of empty vials tomorrow to see if I have the same problem (and work up from there).

Thanks again.

[Peter Apps]

Hi Matthew

Spinning empty vials will not tell you much - it is the weight of the liquid contents that causes a lot of the stress. As a confirmed tinkerer myself I often rig things up with what I have handy, but centrifuges generate a lot more force than you might imagine, and scintilation tubes are just not built for it. What surprises me is the 38 out of the 40 that survived. As an absolute minumum make sure that you have foam between the base of the tube and the plate holder, not just around the sides of the tubes. Good luck, you are going to need it.

Peter

[MaryCarson]

It's the vials. I don't recommend repeating the experiment unless you want to start replacing centrifuge rotors, and even centrifuge itself.

How fast are you spinning things? How important is it to use disposable labware?

[sassman]

Yep, it's probably the vials. Get some centrifuge tubes and you should be OK.

[matthew]

Hi all,

Thanks for the help; as luck would have it, there's someone in the lab that needs a scint vial holder for our robot (tecan) and so I'm pushing the buttons to get something designed. I could just drill something after a home depot trip, but the labware will need to be consistent for the tecan (if we get 2 or more pieces).

Mary, I have spun the vials @ 4500 rpm w/o incident (testing different dispersives), but I get a great drop of perc in ACE when I spin at 2k rpm. I haven't tested lower speeds/longer runs (yet).

sassman, I do have centrifuge tubes that I should (re)consider (also by Kimble), but I've invested a bit in getting things working with this o.d. of scint vial (a rotor for our jouan comes to mind). It's a fair point, so I'll see if I can find a vial with a similar o.d. (27-28mm), with a screw cap, that can be centrifuged.

Thanks again!

[Pragmatist3]

Hi all,

Thanks for the help; as luck would have it, there's someone in the lab that needs a scint vial holder for our robot (tecan) and so I'm pushing the buttons to get something designed. I could just drill something after a home depot trip, but the labware will need to be consistent for the tecan (if we get 2 or more pieces).

Mary, I have spun the vials @ 4500 rpm w/o incident (testing different dispersives), but I get a great drop of perc in ACE when I spin at 2k rpm. I haven't tested lower speeds/longer runs (yet).

sassman, I do have centrifuge tubes that I should (re)consider (also by Kimble), but I've invested a bit in getting things working with this o.d. of scint vial (a rotor for our jouan comes to mind). It's a fair point, so I'll see if I can find a vial with a similar o.d. (27-28mm), with a screw cap, that can be centrifuged.

Thanks again!

Oak Ridge tubes come to mind. Similar o.d., 40 mL and PTFE. They work great for a whole host of partition coefficient, solubility, hydrolysis etc, testing. Any scientific supplier's catalog should have them. I am not familiar with your centrifuge but would be surprised if you could not also find the appropriate cups designed to hold these vessels.