Aquaprobe
®
AP-700, AP-800 & AP-2000 Instruction Manual
10401-00870 Rev R
17.8. 2000-FLU Fluoride Electrode
Fluoride (F) can be measured by the AP-2000 using the optional 2000-CHL ISE electrode
within a pH range of 4 – 8.
The Fluoride ISE electrode will suffer interference from hydroxide (OH-) ions, which are
similar in nature.
17.8.1.
Fluoride Calibration Solution Preparation
When a Fluoride ISE electrode is first installed, it must be calibrated at three points. In
order to achieve this, three batches of Fluoride calibration solution must be prepared.
The solutions required are two 200mL batches of Fluoride at a concentration of 0.5ppm and
one 250mL batch of Fluoride at a concentration of 5ppm.
The three calibration solutions should be freshly prepared by serial dilution from 1000ppm
calibration standard. The following Fluoride standard is recommended:
Part number: SS-709-1610
Description: 500mL Fluoride 1000ppm ISE
Supplier: T E Laboratories Ltd, Ireland.
Contact:
http://www.tellab.ie
Be sure to handle chemicals with care and to read and comply with all health and
safety advice.
Preparing the 5ppm solution
250mL of 5ppm solution is required.
To prepare this, first make an intermediate dilution of 50ppm. To do this, mix 6mL of
1000ppm calibration standard with 114mL of deionised water. This will produce 120mL of
50ppm solution.
Next mix 25mL of the 50ppm solution with 225mL of deionised water. This will produce
250mL of 5ppm solution.
Dispense 200mL of the 5ppm solution into a calibration bottle and retain the rest for
preparation of the 0.5ppm solution.
Preparing the 0.5ppm solution
A total of 400mL of 0.5ppm solution is required. To prepare this, mix 40mL of the 5ppm
solution you have just prepared with 360mL of deionised water. Dispense the 0.5ppm
solution into two calibration bottles (200mL each).
Achieving the correct temperature
During three point calibration, the 5ppm solution and one batch of the 0.5ppm solution must
be at exactly the same temperature. The second batch of 0.5ppm solution must be at least
10ºC cooler.
In order to achieve this, one batch of the 0.5ppm solution should be put into a refrigerator
and the other two solutions should be put into a water bath at 25ºC.
© 2017 Aquaread
®
Ltd.
www.aquaread.com
Page 109 of 141