How to adjust osmolarity of patch pipette filling solution ???

tomte tehgabriel at
Wed Aug 4 09:58:35 EST 2004

Thank you very much for your comments!

Well, i haven't posted it, but when i check my ACSF, its osmolarity is
very close to the value i found in literature (exactly its slightly
above it).  This point suggests to me that the osmometer works fine,
moreover i calibrate it before every use.
Though i use the same compounds for my pipette solution just as i use
for my ACSF, most of the salts seem to be ok.

But i will check it out with a new package of K-gluconate (the main
component of the pipette sol.). And if this does not work  I'll try to
increase osmolarity with sucrose.

Thanks a lot & best regards


> Hi, 
> Most people use sucrose to increase osmolarity, and distilled
> deionized water (e.g., from a MilliQ system) to reduce osmolarity.
> Sucrose isn't charged, so you don't have to worry about it messing
> with your reversal potentials, etc. It's also not a salt, so 1 mM of
> sucrose increases osmolarity by 1 mOsmol.
> I wonder why your solutions are coming out so low, when the calculated
> osmolarity should be 286? some possibilities are:
> 1) You osmometer needs to be calibrated: check it against a solution
> with a known, standard osmolarity. You can probably purchase standards
> from the manufacturer of the osmometer.
> 2) Your salts are old and have taken on moisture, which adds to the
> weight so that the weighed amount contains less salt than it should.
> Matt

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