1. GERDA meeting Dubna 27-29/06/2005
Natural Ge crystal contamination measurement and Isotopic ratio determination by ICP-MS
LNGS Chemistry Service
S. Nisi

2. Analysis method Ge crystal dissolution HNO3+HF+H2O 1:1:1
Dilution of samples and spiked samples preparation to check the procedure
Measurement of contamination and isotopic ratio by ICP-MS Agilent Technologies model 7500a (quadrupole mass analyzer)

3. ICP-MS in the clean room at LNGS

4. Interference on contamination measurement
Element
Interference
11B
10B1H, 22Ne++ N
Air
27Al
31P
15N16O, 30Si1H
69Ga
71Ga
70Ge1H
75As
74Ge1H
113In
115In
73Ge40Ar
121Sb
205Tl
209Bi
232Th
238U

5. Ge93 13196 contamination results
Ge Spike
Element Ge
ppm
Spike conc
Meas. Conc
11B
<0,01
27Al
0,27
0,2
0,32
31P
<2
16,5
39K
<5 42 34
69Ga
0,034
0,032
115In
0,014
0,1
121Sb
0,001
0,01
0,025
205Tl
<0,0021
0,0089
209Bi
<0,0019
<0,0018
232Th
<0,0016
238U
<0,0015
0,0092

6. Ge124 11888 contamination results
Ge Spike
Element Ge
ppm
Spike conc ppm
Meas. Conc ppm
11B
<0,01
27Al
0,22
0,2
0,35
31P
<2
16,5
39K
<5 42 33
69Ga
0,031
0,033
115In
0,0038
0,13
121Sb
0,0013
0,01
0,009
205Tl
<0,0019
0,0093
209Bi
<0,0016
<0,0018
232Th
<0,0014
238U
<0,0013
0,0096

7. Ge crystal contamination comparison
Element
nat Ge X8
ppm Ge Ge
11B
<0,01
27Al
0,32
0,27
0,22
31P
<2
39K
<5
69Ga
0,039
0,034
0,031
115In
0,006
0,014
0,0038
121Sb
0,0036
0,001
0,0013
205Tl
<0,0021
<0,0019
209Bi
<0,0018
<0,0016
232Th
<0,0015
<0,0014
238U
<0,0013

8. Ge isotopic measurement for GNO%
Ge72
Ge73
Ge74
Ge76
Carrier 70Ge
96,47
96,784
1,14
1,090
0,35
0,320
1,46
1,316
0,57
0,490
Carrier 72Ge
0,36
0,355
98,54
98,609
0,23
0,223
0,73
0,683
0,14
0,129
Carrier 74Ge
0,42
0,444
0,64
0,639
0,230
98,5
98,486
0,21
0,201
BLUE VALUE=LNGS measure carried out by ICP-MS (quadrupole mass analyzer)
RED VALUE=MC-ICP-MS (double focusing-multicollector) carried out from ITU of JRC Karlsrhue

9. Ge crystal isotopic ratio measurement
GeX8 % Ge Ge
70Ge
19,08+/-0,10
19,14 +/-0,07
19,18 +/-0,09
72Ge
27,00 +/-0,13
26,95 +/-0,14
26,80 +/-0,09
73Ge
7,81 +/-0,04
7,76 +/-0,04
7,82 +/-0,07
74Ge
37,58 +/-0,21
37,63 +/-0,13
37,61 +/-0,24
76Ge
8,53 +/-0,10
8,52 +/-0,05
8,59 +/-0,05

10. Conclusion
Concerning the contamination measurement of Ge crystal could be possible a little improvement (2or3 factor) of the sensitivity for some elements but we are close to the DL
About the isotopic composition will be possible measure the enriched crystal with the same accuracy and precision