School of Engineering and Science - Jacobs University

16000
0.5 M HCl matrix
a
1.6
14000
1.4
interference on 59 Co in sample solution (cps)
12000
10000
8000
6000
4000
2000
MgCl +
CaO(H) +
MgCl + interference in JDo-1
CaO(H) + interference in JDo-1
1.2
1.0
0.8
0.6
0.4
0.2
interference on 59 Co in sample powder (mg/kg)
0
0.0
0 10 20 30 40 50 60 70 80 90 100
MgO, CaO in sample powder (wt.%)
16000
0.5 M HNO 3
matrix
b
1.6
14000
1.4
interference on 59 Co in sample solution (cps)
12000
10000
8000
6000
4000
2000
CaO(H) +
CaO(H) + interference in JDo-1
1.2
1.0
0.8
0.6
0.4
0.2
interference on 59 Co in sample powder (mg/kg)
0
MgCl +
0.0
0 10 20 30 40 50 60 70 80 90 100
MgO, CaO in sample powder (wt.%)
Figure 11. Mg and Ca interferences on 59 Co as functions of MgO and CaO content in sample powders.
MgO and CaO are calculated as wt.% assuming the sample powders have been diluted by a factor of
1000, which is a typical dilution factor for Mg- and Ca-rich carbonate rocks (primarily dolomites). Top
figure (a) shows interferences observed in HCl matrix, and the MgCl interference on mass 59 predicted
for JDo-1 (18.4% MgO) is >0.6 mg/kg, significantly greater than literature Co values of ~0.2 mg/kg
(see App. 1). Bottom figure (b) illustrates that MgCl interferences are eliminated when samples are
analyzed in HNO 3 , yet significant CaO(H) + interferences predicted for JDo-1 (34.0% CaO) still
preclude accurate determinations of Co. It appears that reasonable Co determinations may only be
possible for typical carbonate samples (MgO, CaO of 5-40%), when Co contents in the rock are at
least one order of magnitude higher than the predicted interference concentrations (i.e., >10 mg/kg).
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