By Anonymous on Tuesday, May 14, 2002 - 04:27 am:
I am working on a small, single use, in-vitro diagnostic device using boronate affinity chromatography. The column is only approx. 5mm diameter x 15mm length and requires a total of 3.6ml of reagent to flow through at atmospheric pressure. The device is enclosed except for small air holes to allow the reagents to flow.
The problem is that bubbles keep forming in the column half-way through the test and this stops the reagents flowing.
It seems to happen mainly when the devices have been stored at 700mbar for 2 weeks, but does sometimes happen when they are freshly made-up.
Does anyone have any experience of this kind of thing?
By Anonymous on Tuesday, May 14, 2002 - 10:53 am:
Sounds like a simple outgassing issue. Have you tried degassing the mobile phase prior to use? You can either vacuum degas the mobile phase or bubble He through to purge out the disolved O2.
By Anonymous on Wednesday, May 15, 2002 - 01:44 am:
Yeah, I tried vacuum degassing but it didn't work. I think He purging is the next thing to try but I feel that the problem may also be a function of the shape of the internal space of the device and the consequent dynamics of air flow through it.
I was just wondering if anyone had experience of small disposable chromatography devices that operate under normal atmospheric pressure?
Thanks for the advice.
By BF on Wednesday, May 15, 2002 - 08:27 am:
I'm not at all familiar with the device you're talking about. The only "small, disposable chromatography devices" I've worked with are solid-phase extraction cartridges. Is your apparatus like those? Is it pre-conditioned before use, or used in a dry condition? What are the solvents you're using, and in what order (if applicable)?
By Anonymous on Wednesday, May 15, 2002 - 08:48 am:
If your plungerseals from your HPLC pump are't really tight, you also get bubbles found on compression.
By Anonymous on Thursday, May 16, 2002 - 09:01 am:
OKAY,
How do I prevent regassing of reagents after, for example, helium sparging? The reagents have to be stored for several weeks before being run. They cannot be degassed immediately before running.
By Jimmy on Thursday, May 16, 2002 - 10:46 am:
You might store the reagents under vaccum,at elevated temperature and/or fill the bottle with helium.
By Jim Gorum on Thursday, May 16, 2002 - 08:27 pm:
No Name,
My experience with single-use (cheap plastic) devices is that flow comes from wetting one part after another so to keep the flow you must have a wick all the way through to a sump (e.g., a pile of absorbent paper would work.)
Jim
By JF on Friday, May 17, 2002 - 01:43 am:
How long should you purge with helium for?
Does it ever affect the composition / reactivity of the reagents?
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