IonPac CS14 Manual
Doc. No. 034848-10
Page 21 of 54
5.6
Selectivity Control of Magnesium, Manganese and Calcium
On-line monitoring of soluble manganese is a good indicator of corrosion in nuclear power plants. Manganese can be
quantified in power cooling waters using the IonPac CS14. Pyrophosphoric acid is added to the methanesulfonic acid eluent
to enhance the resolution of manganese from magnesium and calcium. The pyrophosphate ion complexes preferentially with
the manganese, causing it to elute before magnesium. The pyrophosphoric acid concentration is critical and can be adjusted
to optimize the position of manganese between potassium and magnesium. When pyrophosphoric acid is added to the eluent,
the methanesulfonic acid concentration must be reduced since the pyrophosphoric acid not only complexes with manganese
but also contributes hydronium ions*. This eluent can be suppressed using the AutoSuppression Recycle Mode.
The column can be quickly converted to eluents not containing pyrophosphoric acid by washing the column with 100 mM
methanesulfonic acid for 30 minutes.
Sample Loop Volume:
6.25 µL (2-mm), 25 µL (4-mm)
Analytical Column:
IonPac CS14 Analytical Column
Eluent:
See Chromatogram
Eluent Flow Rate:
0.25 mL/min (2-mm), 1.0 mL/min (4-mm)
SRS Suppressor:
Cation Self-Regenerating Suppressor, CSRS ULTRA (2-mm or 4-mm)
Recycle Mode
or MMS Suppressor:
Cation MicroMembrane Suppressor, CMMS III (2-mm or 4-mm)
MMS Regenerant:
100 mN TBAOH
(tetrabutylammonium hydroxide)
or AES Suppressor:
Cation Atlas Electrolytic Suppressor, CAES
(up to 25 µeq/min)
Expected Background Conductivity:
< 3 µS
Storage Solution:
Eluent
Isocratic Eluent:
4 mM MSA / 5.45 Pyrophosphoric Acid
Isocratic Eluent: 10 mM MSA
*
The higher the concentration of pyrophosphoric acid in the eluent, the faster manganese will elute. Too much pyrophosphoric acid will cause manganese to co-elute with potassium
Figure 5
Selectivity Control of Magnesium, Manganese and Calcium
Analyte
mg/L
1.
Li
+
1.0
2.
Na
+
4.0
3.
NH
4
+
5.0
4.
K
+
10.0
5.
Mg
2+
5.0
6.
Mn
2+
2.5
7.
Ca
2+
10.0
1 mg/L = 1 ppm
Analyte
mg/L
1.
Li
+
1.0
2.
Na
+
4.0
3.
NH
4
+
5.0
4.
K
+
10.0
5.
Mn
2+
2.5
6.
Mg
2+
5.0
7.
Ca
2+
10.0
1 mg/L = 1 ppm
0
5
10
15
μ
S
0
Minutes
1
2
3
4
5
6
5
15
10
7
0
5
10
15
μ
S
0
Minutes
1
2
3
4
5
6
5
15
10
7
