Ion Selective Electrodes (ISE)

nomsmon · Sep 15, 2020

Does anyone have experience with diy solutions utilizing Ion Selective Electrodes?

I haven't heard much about their use in the aquarium industry, but I did find a press release for GHLs ION Director which mentions they developed a multi-Ion Selective Electrode.

Also wondering if ISE in a marine aquarium require a reference EC measurement due to the high conductivity of seawater?

theatrus · Sep 15, 2020

Haven't toyed with them, but they do exist for some interesting types, like Ca+, and a Ca/Mg less-selective type.

https://pim-resources.coleparmer.com/data-sheet/m40501.pdf

ION Director® – GHL (International)

www.aquariumcomputer.com

Looks like its basically a pairing of common electrodes. Those Cole-Parmer models are pricey as expected for an analytical electrode ($300 for Ca+), but probably can be had cheaper from direct imports? I'll need to check around a bit.

IMHO the Ca and Ca/Mg are the most interesting, as it can be a proxy for calcium uptake.

nomsmon · Sep 15, 2020

I was also looking at those Cole-Parmer ones; some very interesting options for sure.

ISE definitely seem to be pricey, but the idea of not having to stock reagents for something like a colorimeter based tester sounds nice.

nomsmon · Sep 15, 2020

The replacement probes for the Pinpoint sensors might be a decent retail option. At ~150USD they are certainly cheaper than the Cole-Parmer or Hanna ISE

theatrus · Sep 15, 2020

nomsmon said:
The replacement probes for the Pinpoint sensors might be a decent retail option. At ~150USD they are certainly cheaper than the Cole-Parmer or Hanna ISE

Good find, curious to do some testing :)

nomsmon · Sep 15, 2020

theatrus said:
Good find, curious to do some testing :)

If you feel up for the adventure I also found a bunch on ali-express, but can't find a datasheet for any... Which puts them outside my comfort zone lol

theatrus · Sep 15, 2020

nomsmon said:
If you feel up for the adventure I also found a bunch on ali-express, but can't find a datasheet for any... Which puts them outside my comfort zone lol

Most seem to resells of the REX electrodes:

Products list direct from CN

Main products PH Probe, Conductivity Probe and 323 more Products from REX (Shanghai) Technology Co.,Ltd. on Alibaba.com

shrex.en.alibaba.com

nomsmon · Sep 15, 2020

Nice find. I tried searching for Rex and couldn't find anything.

I'm guessing these function similar to a pH probe? So connect them to a similar type of voltage measuring circuit?

robsworld78 · Sep 15, 2020

nomsmon said:
Does anyone have experience with diy solutions utilizing Ion Selective Electrodes?

I haven't heard much about their use in the aquarium industry, but I did find a press release for GHLs ION Director which mentions they developed a multi-Ion Selective Electrode.

Also wondering if ISE in a marine aquarium require a reference EC measurement due to the high conductivity of seawater?

No experience but they have a quite a few and what's nice when you view a probe and go to requirements they have plenty of resources to get them working, should be the same for other brands.

Product Category - Vernier

www.vernier.com

theatrus · Sep 15, 2020

nomsmon said:
Nice find. I tried searching for Rex and couldn't find anything.

I'm guessing these function similar to a pH probe? So connect them to a similar type of voltage measuring circuit?

Yeah, looks to be effectively the same. They may require different gain depending on the sensor element range, but thats easy to adjust. Most calibration solutions are two point (10, 1000ppm, or sometimes higher) which is perfectly in range.

theatrus · Sep 15, 2020

robsworld78 said:
No experience but they have a quite a few and what's nice when you view a probe and go to requirements they have plenty of resources to get them working, should be the same for other brands.

Product Category - Vernier

www.vernier.com