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Analytical
method for Molybdenum
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ANALYSIS OF Mo IN Na2MoO4.2H2O
1. Scope
This method describes the X-Ray fluorescence analysis of Mo, within the
following limits :
Mo : 34.00 to 46.00 %
2. Principle
The sample is mixed with a heavy absorber (to compensate for matrix effects)/oxidant
and an internal Standard. The flux is added and the bead is melted in
a muffle furnace, agitated and casted. After polishing the bead is ready
for measurement. Linear calibrations are obtained using an assembly of
synthetic standards prepared from pure oxides. Nb2O5 is used as an internal
Standard.
3. Reagents
- Sr(NO3)2
p.a.
- Li2CO3 p.a.
- Na2B4O7 p.a.
- Nb2O5 specpure.
- MoO3 specpure.
- Na2CO3 p.a.
4. Apparatus
- Philips PW 180 X-Ray fluorescence spectrometer equipped with a LIF220,
chromium/gold
- dual X-Ray tube, scintillation detector, vacuüm path, PHA, collimator
(0.15 mm).
- Philips P3302 computer.
- Muffle furnace at 1200° C.
- Analytical balance 0.0001 g sensitivity.
- Buehler polishing machine.
- Heating plate at 300 to 330 °C.
- Pt/Au or Pt/Au crucible, 70 ml.
- Molds made of duraluminium.
- SiC 80 grit abrasive belt.
5.
Preparation of sample disks
* Composition of the glass disk
0.2500 g sample.
0.2500 g Nb2O5 (internal standard for Mo).
1.0000 g Sr(NO3)2 (heavy absorber/oxidant).
1.0000 g Li2CO3.
(each weight to the nearest 0.1 mg).
10.000 g NaB4O7 (to the nearest 1 mg).
* Preparation
- Mix sample, Nb2O5, Sr(NO3)2, Li2CO3 in the
crucible using a spatula and brush any material adhering to the spatula
into the
crucible .
- Add 10 g NaB4O7 on top of the mixture.
- Place the crucible into the muffle furnace at 1200 °C. Swirl the
crucible after 15
minutes and place it back into the furnace. Pour after 15 minutes the
melt on the
mold. Remove the mold from the heating plate after 5 minutes. Remove the
disk
from the mold after 10 minutes.
- When cool? polish the glass disk.
6. Composition of the standards
Nr |
content |
Mo |
Na2CO3 |
1 |
%
g |
34.00
0.1275 |
0.00939 |
2 |
%
g |
38.00
0.1425 |
0.1049 |
3 |
%
g |
42.00
0.1575 |
0.1160 |
4 |
%
g |
46.00
0.1725 |
0.1270 |
7.
Measuring conditions
Condition |
Mo |
Nb |
Line |
Ka |
Ka |
kV |
90 |
90 |
mA |
30 |
30 |
filter |
out |
out |
collimator |
fine |
fine |
Crystal |
LIF220 |
LIF220 |
meas.time |
10 |
10 |
Background
correction |
yes |
yes |
detector |
Sc |
Sc |
Lower
Level
PHA |
26 |
25 |
Upper
Level
PHA |
77 |
77 |
Background
angle: Mo Ka: +0.80 / Nb Ka: -0.70
8
. Remarks
* Each analysis is done in duplo. The difference for Mo between two single
results must be less then 0.30 %.
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