Im hoping someone can help my pickle -
I ordered potassium d-gluconate and the expected mOsmol for a 130mM Kglu solution is approx 260mOsmol (if I've done my calculations correctly).
However, when I test the compound, the mOsmol is very low - reading of 230mOsmol or 225mOsmol. I contacted the manufacturer(s) and they do not test for osmolarity quality of compounds. Has anyone else noticed a drop in consistency of commerically bought potassium d-gluconate? My go too was Sigma but I have had two batches with very low values and this affects my intracellular quality. Has anyone bought a recent lot which has good osmolarity and will share the information so I can order?
thanks!
Dear Rhiannan it's not a matter of batch. Gluconic acid is weak so its dissociation in water is incomplete. You should increase the amount of K-Gluconate or another component of your solution in order to reach the desired osmolarity.
Hi Mario, thanks for your answer- the idea of simply changing my intercellular constituents to hit the right osmol is ok, to a certain point, but to go from 260osmol up to 290mosmol requires quite a lot of fiddling the components and I’m not comfortable considering the theoretical value of the recipe is 298. Which to me suggests a problem in one of the components itself.
Hey Rhi, Mario is right about poor dissociation of K-Gluconate, it always comes out low. You can add sucrose to make it up to the right osmolarity. We do this and it works pretty well as it will not pass the membrane so basically just maintains the osmolarity without changing the concentration of the intracellular ions.
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