I want to quantify free inorganic phosphate in different milk fractions.
Dear Bjorn, may be a better solution will be to use Ion Chromatogpaphy, or Liquid Chromatography .
http://www.dionex.com/en-us/webdocs/78721-AN210-IC-Phosphate-Content-24Jul2009-LPN2097.pdf
Thank you for your suggestion Mikhail. I was just wondering if such an electrode existed. We also have available ICP-MS and atomic absorption, which we may consider trying as well.
Dear Bjorn, some small companies offer phosphate ISE electrodes, but it for 90% will be too much headache by reason of low reproducibility. ICP or IC will be much better.
Ok. Thanks for both your replies. Probably not the way to go then.
One of the problems with making an electrode for phosphate is the charge on the ion. A trivalent ion such as phosphate suffers from the interferences from many lower valent ions, plus the fact that the sensitivity of a trivalent ISE is only about 20mV/pI. Thus the sensitivity is only one-third that for a univalent ion, further compromising its usefulness. Finally, free phosphate ion doesn't exist in solution except in very basic solutions, so that pH control would be necessary; probably at a value that would denature the proteins in the milk matrix.
Hi
We make an electrode for HPO42- that works very well, with pH management of the solution to be tested.
Best regards
Roy www.aptisens.com
I stand corrected. Roy, I went to your webpage to get more info but, except for learning that you measure the divalent (-2) species at pH 7.4, there was not much more in the way of details. Could you provide more data on its performance? I'm impressed that you've succeeded in developing such an electrode.
Thank you for the info. Very nice. If not proprietary, what do you use as the ionophore?
Sorry, for the multiple replies, but the system indicated that my message couldn't be sent, and I tried a number of options. Next time, I won't believe the error message.
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