[RASMB] Pipette tips for filling centerpieces.

[Leech, AP]

John Philo wrote:
> David and all,
>  
> That was me, and I get those tips from E&K Scientific in Campbell,

> I think other companies probably carry equivalents, but all I can say is
> that these do reach the bottom without enlarging the fill holes. I find that
> with these it is also easier to fill the channel quite full---I routinely
> load 440+ microliters of sample. 
>  
> Best regards,
>  
> John

I use a similar sounding product from Alpha Labs in the UK, their
catalogue number is LW1100 (www.alphalabs.co.uk).

I have found that there is sometimes a problem with using pipette
tips - when the cell is quite full, if any liquid gets up round the
filling hole, then surface tension pulls it between the outside of
the tip and the inside of the hole, effectively creating a seal, so
liquid won't go into the cell but comes back up dyspeptically through
the hole.

To get round this I use a Hamilton gas-tight syringe and an adaptor
to connect the needle to a small piece of silica capilliary tubing
(basically a bit of small bore polythene tubing, a zero-dead volume
union and about 6-7 cm capilliary - if you have a friendly mass spec
lab with low flow HPLC, go and look at their connectors!).

This seems to work well - I get consistent load volumes and the fine
capilliary doesn't block the hole for air egress. The capilliary also
poses less danger of scratching the cell walls than the metal needle.
You do need a steady hand and reasonable eyesight!

NB this system is useless for unloading - the fine capilliary means
you just end up pulling bubbles.

Hope this is useful,

Andrew

-- 
Dr Andrew Leech                   *  Laboratory Manager
Technology Facility               *  Molecular Interactions Laboratory
Department of Biology (Area 15)   *  Tel   : +44 (0)1904 328723
University of York                *  Fax   : +44 (0)1904 328804
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