Transcript Tc-99 Analysis in Air Filters, An Approach to Eliminate

Tc-99 Analysis in Air Filters, An
Approach to Eliminate High
Bias
Mitch Abbate
Barringer Laboratories
Golden, Colorado
Technetium
Discovered in 1937 by Segrè and Perrier
 First Element Produced Artificially
 Fission by-product
 213,000 Year Half-life, Beta Emitter
 Very Soluble
 Can Cause and Help Diagnose Cancer
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Barringer Analysis of Tc-99
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Historically, Tc-99 extracted into TBP
– Messy/ Difficult to meet TAT and MDL
– Mixed Radioactive/ Organic Waste
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Evaluation of Eichrom’s TEVA Resin
– Simpler Procedure
– No Mixed Waste
– Concern over False Positives with Air Filters
Eichrom TEVA Procedure
Oxidize Tc to TcO4-, Tc(VII)
 Pass sample through TEVA Resin (pH=2)
 Rinse Resin with 0.01 N HNO3
 Transfer Resin to LSC Vial
 Add Cocktail
 Count via LSC
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False Positives
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Air Filter Samples
– Pb-210 Possible Culprit
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Pb-210 in U-238 Decay Chain
– Beta Emitter/ Interference with Tc-99
U
U-238
92
U-234
4.4680E+09
99.84%
2.4450E+05
y
Pa234m
1.17m
y
Pa
0.16%
91
Th
90
Th-234
24.1d
Pa234
6.7h
Th-230
77000y
Ac
89
Ra
88
Ra-226
1600y
Fr
87
Rn
86
Rn-222
3.8235d
At
85
Po
84
At-218
0.02%
(~2s )
Po-218
3.05m
Bi
99.979%
Po-214
Po-210
1.637E-04
138.378
s
Bi-214
~100%
d
Bi-210
99.98%
83
Pb
19.9m
Pb-214
~100%
Pb-210
0.021%
82
Tl
5.013d
26.8m
Pb-206
(1.3E-4%)
22.26y
Tl-210
STABLE
Tl-206
(1.7E-6%)
81
Hg
80
1.3m
(4.19m )
Hg-206
(8.5m )
Pb-210?
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Spiked Samples with 500 pCi Pb-210
– Up to 30% Activity Found on TEVA Resin
via LSC
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Tried ppt. Pb w/ FeOH
– Slight Activity Reduction
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Recounted Original Samples
– Significant Activity Drop
– Bi-210 Half-Life 5.01 days
Bi-210
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Ca(PO4)2 ppt.
– Good Results but Too Time Consuming
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Bi uptake in HF on Strong Base Resin
– No Adsorption
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Ref. J.P. Feris, Anal. Chem., 32, 520 (1960)
Re (VII) Uptake
Log Dist. Coeff.
1000
100
[HF]
10
1
0
5
10
15
[HF]
20
HF Evaluation
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HF Added to Load Solution
– Precipitation
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Rinse with HF
– Bi Removed to Near Background
– Some Tc-99 Yield Reduction
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Rinse with HF/Nitric Acid
– Near 100% Tc-99 Recoveries: no Bi or Pb
– TSIE’s best with 5 N HF although 1 N OK
New Air Filter Method
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Tc-99 Leach w/ 1 N Nitric
H2O2 + Heat to Insure TcO4Dilute to < 0.3 N Nitric Acid
Load on TEVA Resin (100-150µ)
25 mL Rinse w/ 0.01 N Nitric
20 mL Rinse w/ 5 N HF-0.01 N Nitric
25 mL Rinse w/ 25 mL 0.01 N Nitric
Direct Addition of Resin to LSC Cocktail
After Dark Adaptation: LSC Counting
TEVA RESIN
Barringer Vacuum Box
Summary
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Method Used for All Sample Types
– Tc-99 yields average >91%
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Batch of 18 Samples (+ 6 QC)
– 6 Hours Total Processing Time
– Two Times Faster than TBP Method
Meeting Required Detection Limits
 Eliminate Mixed Waste
 Eliminate Reruns
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Acknowledgement
Jim Preston, Barringer Laboratories
 Anil Thakkar and Larry Jassin, Eichrom
 Phil Horwitz and Andy Bond, PGRF
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