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The Determination of 224 Ra, 226 Ra, & 228 Ra in Water Samples

The Determination of 224 Ra, 226 Ra, & 228 Ra in Water Samples. Michael Fern Eichrom Technologies, Inc. Background. EPA monitoring of radium in water in US Ra-224 found in drinking water in New Jersey Need for faster method to measure Ra-224 ASTM + US Geological Survey.

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The Determination of 224 Ra, 226 Ra, & 228 Ra in Water Samples

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  1. The Determination of 224Ra, 226Ra, & 228Ra in Water Samples Michael Fern Eichrom Technologies, Inc.

  2. Background • EPA monitoring of radium in water in US • Ra-224 found in drinking water in New Jersey • Need for faster method to measure Ra-224 • ASTM + US Geological Survey

  3. Original Method – Eichrom RAW01(Burnett, et al., 1995) 1 2 0.5-2 L acidified sample Ba-133 3 Load sample in 0.095M HNO3 1 Ln BaSO4 ppt Rinse 0.095M HNO3 2 0.35M HNO3 3 Resin Conversion to BaCO3 226Ra via Rn emanation 223,224Ra via a-spectrometry 1 2 3 0.095M HNO3 228Ra via 228Ac {proportional or HPGe counter} {hold for ~30 hrs.} g-ray measurement Ba-133

  4. 228Ra Results Burnett, et al. 1995

  5. Limitations of Original Method • α-emitters determined by Rn emanation: too long • Need fast method to measure 224Ra (t1/2 = 3.66 days) • 30 hour ingrowth for 228Ac • Conversion of SO42- to CO32- is tedious

  6. 1 1 2 2 3 3 1 2 3 New Approach - RAW03 Load sample at pH 2 (0.5 – 1 L) Evaporate and re-dissolve in 0.095M HNO3 Rinse 50 mL 0.1M HNO3 50 mL 8M HNO3 1 2 3 Load sample in 0.095M HNO3 Cation 1 Ln Ln Rinse 0.095M HNO3 2 • 0.35M HNO3 3 Resin Resin Resin 224, 226Ra via a-spectrometry 1 2 3 To waste 228Ra via 228Ac {proportional or HPGe counter}

  7. Advantages of New Method • No need for 228Ac ingrowth • Eliminate dangerous and inconsistent carbonate conversion • Rapid measurement of α-emitting isotopes • Same day measurement of 224Ra

  8. 226Ra % Recoveries-0.5L DI Water Eichrom data

  9. 226Ra Alpha Spectrum

  10. 226Ra, 224Ra, and Daughters 224Ra 226 Ra 220Rn 218Po 222Rn

  11. 226Ra % Recoveries in Tap water Eichrom data

  12. 226Ra in EPA SampleSept.18, 1998 Eichrom data

  13. 226Ra in NJ Sample Eichrom data

  14. 226Ra in Georgia Inst. Of Tech. Sample# S8933 Eichrom data

  15. 226Ra in Georgia Inst. Of Tech. Sample# WS 14776 Eichrom data

  16. Sample Chemical recovery (Ba-133) Spiked pCi/L (mBq/L) Found pCi/L (mBq/L) A 92.8% 1.16 (42.9) 1.22 (45.1) B 87.1% 5.80 (215) 5.73 (212) C 84.3% 11.6 (429) 11.7 (433) 226Ra ResultsHerbert, USEPA 2002

  17. Sample Chemical recovery (Ba-133) Spiked pCi/L (mBq/L) Found pCi/L (mBq/L) A 92.8% 32.8 (1210) 32.0 (1180) B 87.1% 10.9 (403) 11.9 (440) C 84.3% 4.37 (162) 4.54 (168) 228Ra ResultsHerbert, USEPA 2002

  18. Ca and Mg Interference in 500 mL Samples Eichrom data

  19. Ca Interference in 100 mL of Sample Eichrom data

  20. Detection Limits – 226RaUS EPA Requires: 37 mBq/L

  21. Summary • <37 mBq/L detection limits achievable • Eliminates inconsistent carbonate conversion • Faster measurement of 224Ra • High amounts of Ca and Mg interferences handled well with 100 mL samples • Acceptable 226Ra and 228Ra recoveries

  22. Special thanks to: • Anil Thakkar, Eichrom Technologies • David McCurdy & Ann Cleveland, ASTM • Dr. B. Parsa, New Jersey department of health, NJDr. B. Kahn, Georgia Institute of Technology, GA • References: • Burnett, W.C., Cable, P.H., & Moser, R.; Determination of Ra-228 in Natural Waters Using Extraction Chromatography, Radioactivity & Radiochemistry, vol. 6, no. 3 (1995) • Herbert, V., USEPA NAREL, Single Operator Test Report, ASTM Test Method: Ra in Water; presented at RRMC, Knoxville, TN 11/2002.

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