Ammonium Electrode
Instruction Manual
8
Li
+1
2.0X10
1
2.0
2.0X10-
1
Na
+1
2.0X10
1
2.0
2.0X10-
1
+Tris
+1
is the cation of tris(hydroxymethyl)aminomethane
Interference
(ppm)
100 ppm NH
4
+
10 ppm NH
4
+
1 ppm NH
4
+
Cs
+1
1.0X10
2
1.0X10
1
1.0
K4
+1
2.7X10
2
2.7X101 2.7
Tl
+1
3.1X10
3
3.1X10
2
3.1X10
1
H
+1
1.6 pH
2.6 pH
3.6 pH
Ag
+1
2.7X10
5
2.7X10
4
2.7X10
3
+Tris
+1
3.1X10
5
3.1X10
4
3.1X10
3
Li
+1
3.5X10
4
3.5X10
3
3.5X10
2
Na
+1
1.1X10
5
1.1X10
4
1.1X10
3
Temperature Influences
Samples and standards should be at the same temperature, since electrode potentials are influenced
by changes in temperature. A 1oC difference in temperature results in a 2% error at the 1.0X10-
3
M
level.
Provided that temperature equilibrium has occurred, the ammonium ion electrodes can be used at
temperatures from 0o-50oC continuously and 40o-50oC intermittently. Room temperature
measurements are recommended, since measurements at temperatures markedly different from
room temperature may require equilibrium times up to one hour. Table 4 indicates the variation of
theoretical slope with temperature.
TABLE 4: Temperature vs Value for the Electrode Slope
Temp
(oC)
S"(slope)
0
54.20
10
56.18
20
58.16
25
59.16
30
60.15
40
62.13
50
64.11