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Forum index » Science and Technology » Chem » Electrochem
Fluoride measurement: ISE vs. IC
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liujx7@yahoo.com
science forum beginner


Joined: 21 Jul 2006
Posts: 4

PostPosted: Fri Jul 21, 2006 1:35 pm    Post subject: Re: Fluoride measurement: ISE vs. IC Reply with quote

Thermo said their ISE electrode usually is good for a year. How about
Metrohm ones? Do they last? Do you know the detection limit?

Thanks!


cssabern@gmail.com wrote:
Quote:
I used Metrohm ISE electrodes (for F-) every year for 2nd year college
students' experiments on physical chemistry.
It works well.

----------------------------------------------------------------------------------------------
Jessi wrote:
Does anyone know about the quality of Metrohm electrodes?
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cssabern@gmail.com
science forum beginner


Joined: 21 Jul 2006
Posts: 1

PostPosted: Fri Jul 21, 2006 8:00 am    Post subject: Re: Fluoride measurement: ISE vs. IC Reply with quote

I used Metrohm ISE electrodes (for F-) every year for 2nd year college
students' experiments on physical chemistry.
It works well.

----------------------------------------------------------------------------------------------
Jessi wrote:
Does anyone know about the quality of Metrohm electrodes?
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liujx7@yahoo.com
science forum beginner


Joined: 21 Jul 2006
Posts: 4

PostPosted: Fri Jul 21, 2006 4:44 am    Post subject: Fluoride measurement: ISE vs. IC Reply with quote

I am trying to measure low-level of fluoride (hopefully below 0.01 ppm)

in a defined bacterial medium with about 400 ppm of chloride and 1000
ppm of phosphates. I would like to get some opinions about which method

is better. So far I didn't have success with either of the method.

My ISE (IonPlus from Thermo) was about two years old, but it was only
used it for a week last year. It was stored dry as suggested in the
manual, but there was a little crystallization probably because the
filling solution wasn't completely rinsed out last time. The reading
slowly drifted and I can't get a stable reading after waiting for a
couple of hours. The technical support from Thermo said the electrode
should be good for a year and beyond that it is hard to say. I guess
the electrode is just too old. I don't have good luck with Thermo
electrodes. Does anyone know about the quality of Metrohm electrodes?


I also tried IC with IonPac AS11-HC column, but I only got detection
limit about 0.2 ppm. The IC system is a three-year old Dionex system,
and has been maintained well. The analytical column is about 2 years
old, and I don't know how heavily it has been used. The chloride and
fluoride peak are well separated, so I don't think high level of
chloride was a problem. I wonder what kind of detection limit you
usually get with IC?


Any suggestion or experience is highly appreciated! Thank you.
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