Post on 30-Jan-2021
Österreichische Agentur für Gesundheit und Ernährungssicherheit GmbH www.ages.at
Determination of Pb-210 and Po-210 in Water Using the Extractive Scintillation
Cocktail Polex™
Claudia Landstetter Dept. Radiation Protection and Radiochemistry
LSC - Conference
Barcelona, 18.3.13 – 22.3.13
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•Method used for many years in our lab
•Lot‘s of Drinking water samples
•Mineral water samples
•Ground water samples
www.ages.at 3 Claudia Landstetter, 20.03.13
210Pb, 210Po separation and determination by LSC
1 L of water sample + 1.6 mg lead carrier
precipitation with 1 M Na2S at pH 1.5 pH 10
dissolved in 12 ml 7.5 M H3PO4 + 2 ml 1 M HCl
stored for 2 weeks
210Bi and 210Po are selectivly extracted with Polex
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210Pb, 210Po separation and determination by LSC
• Figure 1: Spectrum of 210Bi, extracted with Polex after reaching radioactive equilibrium with 210Pb. The two bars define the selected range for the analysis.
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210Pb, 210Po separation and determination by LSC
• Figure 2: Spectrum of 210Po extracted with Polex. The two bars define the selected range for the analysis.
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- Good results with nice spectra for drinking water samples
- Problems with ground water samples
- Additional peaks from the uranium isotopes
- Po-210 5,3 MeV
- U-234 4,8 MeV
- U-235 4,4 MeV
- U-238 4,2 MeV
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160 µg/L U-238
0.12 µg/L U-238
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0.89 µg/L U-238
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0.94 µg/L U-238
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15 µg/L U-238
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22 µg/L U-238
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Spectra of Standardsolutions extracted with Polex
• ICP-MS standard solution of 160 µg/L U-238 in 1 M HCl and 7.5M H3PO4 extracted with Polex
• Check it the uranium is extracted
• Chemical composition of the solution is important
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22 µg/L U-238
• Green: Ground water sample
• Blue: Addition of Pb-210 standard solution before the extraction
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210Pb, 210Po, uranium separation
• Uranium dissolves in the acidic solution
1 L of water sample + 1.6 mg lead carrier
precipitation with 1 M Na2S at pH 1.5 pH 10
Precipitate is washed with 1% HNO3
dissolved in 12 ml 7.5 M H3PO4 + 2 ml 1 M HCl
stored for 2 weeks
210Bi and 210Po are selectivly extracted with Polex
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Drinkingwater with 3.2 µg/L U-238
0
10
20
30
40
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60
70
80
90
Remaining Solution after theprecipitation
first time 10ml 1% HNO3 second time 10ml 1% HNO3 sample solution after solvingthe precipitate
Pe
rce
nta
ge
%
Pb-208 U-238
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0,0
10,0
20,0
30,0
40,0
50,0
60,0
70,0
80,0
90,0
Remaining Solution after the precipitation first time 10ml 1% HNO3
Pe
rce
nta
ge %
DW Pb-210
DW U-238
DW Pb-210
DW U-238
GW Pb-210
GW U-238
GW Pb-210
GW U-238
• DW Drinkingwater 0.16 µg/L U-238
• GW Ground water 16 µg/L U-238
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Chemical recovery
• Addition of the lead carrier and measurement with the ICP-MS
• Using Po-209 spike and alphaspectrometry as reference measurement Addition at the beginning Addition after the precipitation
• Spiked samples with Pb-210 standard solution (possibility to check the extraction step)
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chemical recovery
1 L of water sample + 1.6 mg lead carrier
precipitation with 1 M Na2S at pH 1.5 pH 10
Precipitate is washed with 1% HNO3
dissolved in HClkonz
½ Alphaspectroscopy
½ LSC with Polex
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• The chemical recovery is higher for Po-210 than for Pb-210
• Red bar is taken as chemical recovery for the calculation in analysis
• Compareable results with the different measurements
0102030405060708090
100110
DW 59 mBq Pb-210/Po-210
DW 59 mBq Pb-210/Po-211
MW 39 mBq Pb-210, Po-210
MW 39 mBq Pb-210, Po-211
MW 39 mBq Pb-210, Po-212
chemical recovery of lead before theautodepositon
chemical recovery of lead after the extraction
chemical recovery of Pb-210 LSC
chemical recovery Po-210 from LSC
chemical recovery Po-210 alpha
chemical recovery Po-209 alpha
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Drinkingwater sample from Upper Austria
•5 bottels were taken
•5 Rn-measurements
Rn-222 Activityconcentration
Sample 1 1426 ± 86 Bq/L
Sample 2 1360 ± 82 Bq/L
Sample 3 1386 ± 83 Bq/L
Sample 4 1417 ± 85 Bq/L
Sample 5 1431 ± 86 Bq/L
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Drinkingwater sample from Upper Austria
• 2 Samples were analysed with LSC and Polex-extraction
• 2 Samples were analysed with autodepositon and alpha spectrometry
• 1 Sample was analysed with autodeposition and LSC after dividing the sample into 2 parts after the PbS precipitation.
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Drinkingwater sample from Upper Austria
Polex and LSC Po-210 [mBq/L]
Autodeposition and alpha Po-210 [mBq/L]
Sample 1 202 ± 28
Sample 2 170 ± 24
Sample 3 190 ± 27 195 ± 24
Sample 4 185 ± 23
Sample 5 186 ± 22
• Sample 3: Po-209 was added after the dividing of the sample
• Sample 4+5: Po-209 was added at the beginning of the sample praparation
• Values are not corrected with the ingrown Po-210 from Pb-210 and Rn-222
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Drinkingwater sample from Upper Austria
chemical recovery of lead before the autodepositon
Chemical recovery of Po-209 after autodeposition
chemical recovery of lead before the extraction
chemical recovery of lead after the extraction
Sample 1 91 %
Sample 2 96 %
Sample 3 100 % 100 % 96 % 93 %
Sample 4 100 % 90 %
Sample 5 98 % 107 %
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- Ingrowth of 210Pb from 222Rn
- Ingrowth of 210Po from 222Rn and 210Pb
- 222Rn should be measured shortly after the sampling
- Storage time until the further analyses for 210Pb and 210Po should be as short as possible
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LLD Pb-210
Activity-concentration [mBq/L]
Rn-222 23.5 · 103
Time between sampling and evaporation
2.0 days
Pb-210 measured 7.2 ± 3.2
Pb-210 ingrowth calculated from Rn-222
3.41 ± 0.25
LLD (Rn = BG) 1.6
Pb-210 value after correction
3.8 ± 3.0
LLD (measurement) 1.7
0
2
4
6
8
10
Pb-210measured
Pb-210ingrowth
calculated fromRn-222
LLD (Rn = BG) Pb-210 valueafter correction
Acti
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ntr
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LLD Po-210
6,2
1,1 1,2
4,4
0,5
0
1
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4
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6
7
8
9
Po-210 measured Po-210 ingrowth calculatedfrom Rn-222
LLD (Rn,Pb = BG) Po-210 value aftercorrection
LLD (measurement)
Act
ivit
yco
ncn
etr
atio
n [
mB
q/L
]
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LLD Pb-210
Activity-concentration [mBq/L]
Rn-222 242 · 103
Time between sampling and evaporation
5.5 days
Pb-210 measured 79 ± 14
Pb-210 ingrowth calculated from Rn-222
72.9 ± 4.4
LLD (Rn = BG) 7.4
Pb-210 value after correction
6 ± 15
LLD (measurement) 4.0
0
10
20
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80
90
Pb-210measured
Pb-210ingrowth
calculated fromRn-222
LLD (Rn = BG) Pb-210 valueafter correction
Acti
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[m
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LLD Po-210
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• The chemical recovery is higher for Po-210 than for lead
• The chemical recovery calculated from measuremets of the lead with the ICP-MS can be taken to control the chemical recovery of the Po-210
• The only step without determination of the chemical recovery is the extractionstep with Polex. Here still uncertainties exist depending on the matrix of the sample.
• With the precipitation and the washing with 1 % HNO3 eliminates most of the interfering substances. Eg. The uranium, which is also extracted from ground water samples.
• If problems occur the sample can be split into 2 parts and 1 can be extracted and the other part can be spiked with Pb-210 before the extraction.
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• Measurements with alpha deposition show good agreement • The ingrown Pb-210 and Po-210 has to be substracted
• Problems can occure because of high Radon activity concentrations and long storage times.
• For the determination of the LLD the ingrown Pb-210 and Po-210 have to be taken into account.
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Thank you for your attention
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•
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160 µg/L U-238
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• Green: Ground water sample
• Blue: Addition of Pb-210 standard solution before the extraction
15 µg/L U-238
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LLD Pb-210
Activity-concentration [mBq/L]
Rn-222 95 · 103
Time between sampling and evaporation
3 days
Pb-210 measured 21.8 ± 5.1
Pb-210 ingrowth calculated from Rn-222
19.6 ± 1.2
LLD (Rn = BG) 3.8
Pb-210 value after correction
2.27 ± 5.3
LLD (measurement) 2.1
0
5
10
15
20
25
Pb-210measured
Pb-210ingrowth
calculated fromRn-222
LLD (Rn = BG) Pb-210 valueafter correction
Acti
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[m
Bq
/L
]
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LLD Po-210