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Aquaprobe
®
AP-7000 Instruction Manual
10401-00894 Rev M
16.4. 7000-AMM Ammonium/Ammonia Electrode
Ammonium (NH4) and Ammonia (NH3) can be measured by the AP-7000 using the
optional 7000-AMM ISE electrode within a pH range of 5 – 8.
The Ammonium ISE electrode will suffer interference from Potassium, Sodium and
Magnesium ions, which are similar in nature.
16.4.1.
Ammonium Calibration Solution Preparation
When an Ammonium ISE electrode is first installed, it must be calibrated at three points. In
order to achieve this, three batches of Ammonium calibration solution must be prepared.
The solutions required are two 400mL batches of Ammonium (as NH4) at a concentration
of 10ppm and one 400mL batch of Ammonium (as NH4) at a concentration of 100ppm.
The three calibration solutions should be freshly prepared by serial dilution from 1000ppm
calibration standard. The following Ammonium standard is recommended:
Part number: SS-702-1610
Description: 500mL Ammonium 1000ppm as NH4 ISE
Supplier: T E Laboratories Ltd, Ireland.
Contact:
Be sure to handle chemicals with care and to read and comply with all health and
safety advice.
Preparing the 100ppm solution
500mL of 100ppm solution is required. To prepare this, mix 50mL of 1000ppm calibration
standard with 450mL of deionised water.
Dispense 400mL of the 100ppm solution into a calibration cup and retain 100mL for
preparation of the 10ppm solution.
Preparing the 10ppm solution
A total of 800mL of 10ppm solution is required. To prepare this, mix 80mL of the 100ppm
solution you have just prepared with 720mL of deionised water. Dispense the 10ppm
solution into two calibration cups (400mL each).
Achieving the correct temperature
During three point calibration, the 100ppm solution and one batch of the 10ppm solution
must be at exactly the same temperature. The second batch of 10ppm solution must be at
least 10ºC cooler.
In order to achieve this, one batch of the 10ppm solution should be put into a refrigerator
and the other two solutions should be put into a water bath at 25ºC. Once all three
solutions are at a stable temperature, calibration can begin.
16.4.2.
Three-point Calibration
During three-point calibration, the AP-7000 and Aquameter
®
must remain switched on. If
the Aquameter
®
is switched off between points, the calibration process will be aborted and
must be re-started from point 1. The AP-7000's sleeve and wiper should also be removed
in order to reduce the Probe's thermal mass. To calibrate the ISE electrode follow these
steps:
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®
Ltd.
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