[AG@BUGSS]

Hi all,
I'm looking into a project measuring the amounts of sodium sequestered in yeast vacuoles.
Unfortunately, I'm working in a biology lab with limited chemical expertise and equipment. Additionally, I have a tiny (nonexistent) budget, so buying an ion-selective electrode is out of the question. I've found some tests in the literature involving ion exchanges, but nothing that involves safe, cheap reagents that could be brought into a bio lab without a fume hood. I can probably find the use of that kind of basic equipment if I ask nicely, though.

Does anyone know of a safe and cheap technique for measuring sodium concentration? Titration, precipitation, something else I've never heard of, it doesn't matter as long as its (relatively) safe and doesn't cost too much.

Thanks!

[Arkcon]

I'm afraid that sooner or later, you're going to come right up against a wall with this plan of yours.  Sodium is very hard to precipitate, and titrate.  Adding to that, you want to quantitate tiny amounts, I would guess.  You've made a difficult problem even harder.

[AG@BUGSS]

Yeah, I'm starting to get that impression. My plan at this point is to remove the cells from the cultures and dehydrate the media in the hopes that there will be a measurable difference in mass. It's far from ideal, but it works with the tools I have.

Would chloride be any easier to work with? From what I've read, most of the investigation into salt tolerance has focused on sodium, as cells seem to have a harder time managing it than chloride.

[Furanone]

Chloride would definitely be easier to determine with a very simple Mohr's or Volhard Titration with silver nitrate and potassium chromate as indicator. As to the correlation between Na and Cl in your system, I cannot answer that, but they are usually the two most common salt ions (cation and anion, respectively).

[billnotgatez]

If Potassium is in the system would that interfere with using Chlorine to measure Sodium level?