I would like to get a quick estimation of total Ca content in soy concentrates.
I was thinking that by acidifying and heating I can solubilize the majority of the Ca and measure it with an ion selective electrode.
any experience and suggestions?
Hello,
I don't have experience in ion selective electrodes, but acidification per se should only solubilze Ca in mineral form, no guarantee to release it from macromolecules. Helation might work better.
I suggest breakdown and AAS or ICP-MS analysis.
Thanks Miloš and Monika.
Nice to meet fellow people from Ljubljana =) on research gate.
I'm searching for a relay quick / easy / cheap solution. So as we are routinely using it the ion-selective electrode is the best tool for me right now.
I'll try your suggestion Monika, let you know how it worked!
Tanks again!
Hello, another one from the same bunch chiming in. :) I hope you won't have too much trouble with the ion-selective electrode, because organic molecules can heavily obstruct the access of ions to the sensor surface and skew your results (personal experience) ... The least you can do is filter or ultracentrifuge the soy concentrate after acidification; you will remove at least a fraction of organic matter. However, as Miloš pointed out, there is a possibility that you will remove a fraction of Ca2+ along with it. It depends on how strongly the contents of your concentrate bind Ca2+, though ... The standard approach to the total ion determination is the one described by Monika.
If you really have no other option than the ion-selective electrode, then be sure to use the method of standard additions instead of the direct calibration. It will help to compensate for interferences to a certain degree.
Good luck!
Hi Tea,
Which electrode do you use? What kind of membrane?
We have the Ca-ISE perfecION from Mettler Toledo, whit an polymere membrane, and I haven't noticed any problems in samples with organic mater. The only major problem is oil! Even if it is present in really small amounts it heavily influences the measurement - majorly increasing the response time, reducing the slope....
We have Ag/S2 combination electrode, also from Mettler Toledo, with a solid-state sensor surface. What you are experiencing with oil is a typical interference in ion-selective potentiometry. Perhaps your electrode is less sensitive to other organic compounds because polymer-based ion-selective electrodes have ion carriers included in the membrane and operate under a slightly different principle than solid-state based electrodes. With our electrode, measurements in a complex matrix are next to impossible. Just to clarify - in case someone from Mettler Toledo will be reading this ;) - it's not the issue of the manufacturer, but of the principle how ion-selective potentiometry works.
- Badges
- Science topic
- Similar topics
- Microbiology
- Assays