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

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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

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Remaining Solution after theprecipitation

first time 10ml 1% HNO3 second time 10ml 1% HNO3 sample solution after solvingthe precipitate

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Pb-208 U-238

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Remaining Solution after the precipitation first time 10ml 1% HNO3

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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

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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

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Pb-210measured

Pb-210ingrowth

calculated fromRn-222

LLD (Rn = BG) Pb-210 valueafter correction

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LLD Po-210

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Po-210 measured Po-210 ingrowth calculatedfrom Rn-222

LLD (Rn,Pb = BG) Po-210 value aftercorrection

LLD (measurement)

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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

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Pb-210measured

Pb-210ingrowth

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LLD (Rn = BG) Pb-210 valueafter correction

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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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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

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Pb-210measured

Pb-210ingrowth

calculated fromRn-222

LLD (Rn = BG) Pb-210 valueafter correction

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LLD Po-210