ISE Meter range

[rafik]

Hi Everybody,

I am new in this forum but ready to lern from you.
So, there is somenthing that does not leave me quiet, it is about ISE Meters.
The Jenco 6250 pH/ion meter has as maximum range of meassure in the ion meter mode: 119.8 conc.
Somebody knows what is the meaning of this abbreviation "conc." and how could I convert to ppm?
I supouse it is very simple but for me it is very hard. It is not my matter.
Please somebody could give me a hand!!!
Regards

[Tom Barr]

ISE's are good if you can remove or inactivate the interfering ions. But for aquariums, this is tough unless you take a subsmaple of the water out, then add chemical etc to it, then take the measure.
Regular test kits do the same thing. You also need to calibrate the ISE probe and make a slope and standards for the ion of interest(just like a pH meter).

They have little use for aquariums.

119.8 is likely 119.8%. They also refer to a mV range that goes to about 750mV.
You will get an error above that.

I'd just call/email them and ask,

[Biollante]

Hi,

I realize this will likely elicit profanity-laced responses from the Guru team, but here goes…

First off there is no magic, you will still need to understand a little chemistry and math.

Next as with most things that are worthwhile, it is all about the preparation and realistically you will always sample and prepare the samples… More on that later if you or anyone else is interested.

Tom Barr is as usual correct, if not exuding confidence; the “conc.” is indeed concentration as a percentage. In your case there are three ranges for ionic strength 0.0 (0.05 actual) to 25, 25 to 50 and 50 to 119.8. With 120 corresponding to 750-Mv.

The conversion of Molarity to ppm is the molecular weight equal to the concentration in ppm at 10^-3M. For example, Calcium has a molecular weight of 40.1, so 10^-3M concentration is equal to 40.1- ppm. Therefore, 1-ppm Calcium equals 2.5 X 10^-5M.

The Jenco 6250 is a nice device for a serious hobbyist.

For Ion selective electrode (ISE), the magic lies within the membranes.

There are sampling techniques and so on, but taking Calcium measurement as an example, you should be able to get very close, repeatable measurements from 1M (40,100-ppm) down to 5 X 10^-7M (0.02-ppm).

Calcium is nice as the pH range, nicely aquarium, is 6-8. Make sure the temperature remain steady from sampling to test.

Again check your manual but filling solution is 0.1M KCl (molecular weight is 74.5515g/mol) so you guessed it 0.7455-g KCl/100-ml and an ISA/buffering solution of 1M KCl. (I have found many of the problems folks complain about are avoided by always using a couple milliliters of ionic strength adjusters (ISA).)

Follow all the procedures for setting and calibrating your probe. A magnetic stirrer is handy, some electrodes have built in stirrers, I have found standalone stirrers work best for me, the idea is to keep good constant motion with as little agitation as possible.

Biollante