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November 10, 2009
Lab Equipment: Any H-Cube Troubleshooters Out There?
I mentioned the H-Cube hydrogenation machine here a couple of years ago as an early example of a commercial flow chemistry machine. As some readers may have guessed, my recent post on hydrogenations was partly inspired by a recent run of activity on this instrument, which came in quite handy.
Until the last couple of days, that is. Now there's a problem, and I'd be glad to hear from any H-Cube users who might know how to solve it. (If you haven't used one, you can probably bail out right now!) What's going on is: when I try to run a hydrogenation in "Full H2" mode, everything works fine until the H2 valve closes. The pump's fine, the flow through the instrument is fine. . .until the status switches to "Running". At that point the flow stops momentarily, then a gout of solvent runs from the outlet all at once, and then. . .nothing. Well, nothing except hydrogen gas - if I dip the outlet tube below the surface of some solvent, I can see that it's still producing that. But there's no flow. Lifting the solvent inlet from the reservoir, I can see that nothing's being taken up - an air bubble forms at the inlet, and just moves up and down.
So there's something going on when the system starts letting hydrogen into the flow, but I'm not sure what that might be. I can always call in the $250/hr folks, but I thought that throwing my problems out onto the blog was at least worth a try. Just to take care of some obvious fixes, so far I've cleaned the metal frit, replaced the Teflon membrane, sonicated the check valve, and tried changing catalyst cartridges. Anyone got any clues after that?
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