Ammonium Electrode
Instruction Manual
6
11.
Immerse the electrode tip(s) in the solution and wait for the reading to stabilize. Read the
concentration directly from the meter display.
12.
The electrodes should be re-calibrated every 1-2 hours. Simply repeat Steps 2-8 (2-9)
above.
Low Level Ammonium Determination (using a standard pH/mV meter)
This procedure is recommended for solutions with ionic strengths less than 1.0 x 10-
2
M. If the
solution is high in ionic strength, but low in ammonium, use the same procedure, but prepare a
calibration solution with a composition similar to the sample.
1.
Using 20 ml of stock ISA, dilute to 100 ml with distilled water.
2.
Dilute 1 ml of the 0.1M standard to 100 ml to prepare a 1.0x10-
3
M standard solution for
measurements in moles per liter. Dilute 10 ml of the 1,000 ppm standard to 100 ml to
prepare a 100 ppm standard solution for measurements in ppm.
3.
To a 150 ml beaker, add 100 ml of distilled water and 1 ml of low level ISA. Place the
beaker on the magnetic stirrer and begin stirring at a constant rate.
4.
Place the electrode tip(s) in the solution. Assure that the meter is in the mV mode.
5.
Add increments of the 1.0x10-
3
M or 100 ppm standard as given in Table 2 below.
6.
After the reading has stabilized, record the mV reading after each addition.
TABLE 2: Stepwise Calibration for Low Level Ammonium Measurements
Added
Concentration
Step
Pipet
Volume
(ml) M
ppm
1
A
0.1
1.0X10-
6
0.1
2
A
0.1
2.0X10-
6
0.2
3
A
0.2
4.0X10-
6
0.4
4
A
0.2
6.0X10-
6
0.6
5
A
0.4
9.9X10-
6
1.0
6
B
2
2.9X10-
5
2.9
7
B
2
4.8X10-
5
4.8
Pipet A = 1 ml graduated pipet
Pipet B = 2 ml pipet
7. On semi-logarithmic graph paper, plot the mV reading (linear axis) against the
concentration (log axis) as in Figure 1.
8.
Rinse the electrode(s) in distilled water and blot dry.
