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Aspects on the analysis of (210)Po.

Henricsson, Fredrik LU ; Ranebo, Ylva LU ; Holm, E and Roos, P (2011) In Journal of Environmental Radioactivity 102(5). p.415-419
Abstract
There has been little development regarding analysis of polonium (Po) in environmental samples since the 1960ies. This is due to the straightforward spontaneous deposition of this element on silver (Ag), nickel (Ni) or copper (Cu) without any radiochemical separation. For many years, no radiochemical yield determinant was used and it was generally supposed that the yield was 100% after two depositions. Counting was often done using ZnS scintillation counter coupled to a photomultiplier tube. However, the use of the yield determinants (208)Po and (209)Po and the development of alpha spectrometry showed that the yield was lower. Furthermore, the tendency of Po to volatilize at low temperatures constrains the sample preparation techniques;... (More)
There has been little development regarding analysis of polonium (Po) in environmental samples since the 1960ies. This is due to the straightforward spontaneous deposition of this element on silver (Ag), nickel (Ni) or copper (Cu) without any radiochemical separation. For many years, no radiochemical yield determinant was used and it was generally supposed that the yield was 100% after two depositions. Counting was often done using ZnS scintillation counter coupled to a photomultiplier tube. However, the use of the yield determinants (208)Po and (209)Po and the development of alpha spectrometry showed that the yield was lower. Furthermore, the tendency of Po to volatilize at low temperatures constrains the sample preparation techniques; dry-ashing cannot be used. But during the wet-ashing procedure, there are still some losses. The aim of this study was to evaluate the Po losses during wet-ashing by the use of a double-tracer technique. We have found that the losses were about 30% when open glass beakers were used and about 17% when the samples were digested in microwave oven. When long-necked bottles (Kjeldahl flasks) were used, a loss of about 20% was registered. It has also been observed that (210)Pb to some extent is plating out together with its daughter nuclide Po during the electrochemical deposition. This will result in a systematic error since an unknown amount of supported (210)Po will be produced from the (210)Pb decay depending on the fraction of (210)Pb being deposited on the disc and the waiting time between deposition and measurement of the sample. A further consequence of this is that in the assessment of the (210)Pb content in the sample, very often the remaining liquid is stored after deposition for build-up of (210)Po. Since some (210)Pb is lost on the disc, the result for (210)Pb will be too low. Both these systematic errors give rise to a too high (210)Po/(210)Pb ratio. The fraction of (210)Pb which is plating out has been assessed in this study for different matrices and is about 50-90%. During the measurement by solid state Si-detectors, some Po is evaporated in the vacuum conditions contaminating the detectors. Experiments have here been done by heating the discs after deposition which indicate that less Po is evaporated from Ag than from Ni. The losses from Ag are less than that from the other metals probably due to a deeper penetration into the surface of Po. We conclude that in most aspects, Ag is better to use than the other plating metals. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bi-210, Po-210, Pb-210, Radiochemical analysis, Plating, Spontaneous, deposition
in
Journal of Environmental Radioactivity
volume
102
issue
5
pages
415 - 419
publisher
Elsevier
external identifiers
  • wos:000291287100002
  • pmid:20970897
  • scopus:79955477245
ISSN
1879-1700
DOI
10.1016/j.jenvrad.2010.09.010
language
English
LU publication?
yes
id
6421cc45-7ee8-4c27-8e42-852e7a098948 (old id 1710829)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/20970897?dopt=Abstract
date added to LUP
2010-11-05 14:01:07
date last changed
2017-11-12 03:07:57
@article{6421cc45-7ee8-4c27-8e42-852e7a098948,
  abstract     = {There has been little development regarding analysis of polonium (Po) in environmental samples since the 1960ies. This is due to the straightforward spontaneous deposition of this element on silver (Ag), nickel (Ni) or copper (Cu) without any radiochemical separation. For many years, no radiochemical yield determinant was used and it was generally supposed that the yield was 100% after two depositions. Counting was often done using ZnS scintillation counter coupled to a photomultiplier tube. However, the use of the yield determinants (208)Po and (209)Po and the development of alpha spectrometry showed that the yield was lower. Furthermore, the tendency of Po to volatilize at low temperatures constrains the sample preparation techniques; dry-ashing cannot be used. But during the wet-ashing procedure, there are still some losses. The aim of this study was to evaluate the Po losses during wet-ashing by the use of a double-tracer technique. We have found that the losses were about 30% when open glass beakers were used and about 17% when the samples were digested in microwave oven. When long-necked bottles (Kjeldahl flasks) were used, a loss of about 20% was registered. It has also been observed that (210)Pb to some extent is plating out together with its daughter nuclide Po during the electrochemical deposition. This will result in a systematic error since an unknown amount of supported (210)Po will be produced from the (210)Pb decay depending on the fraction of (210)Pb being deposited on the disc and the waiting time between deposition and measurement of the sample. A further consequence of this is that in the assessment of the (210)Pb content in the sample, very often the remaining liquid is stored after deposition for build-up of (210)Po. Since some (210)Pb is lost on the disc, the result for (210)Pb will be too low. Both these systematic errors give rise to a too high (210)Po/(210)Pb ratio. The fraction of (210)Pb which is plating out has been assessed in this study for different matrices and is about 50-90%. During the measurement by solid state Si-detectors, some Po is evaporated in the vacuum conditions contaminating the detectors. Experiments have here been done by heating the discs after deposition which indicate that less Po is evaporated from Ag than from Ni. The losses from Ag are less than that from the other metals probably due to a deeper penetration into the surface of Po. We conclude that in most aspects, Ag is better to use than the other plating metals.},
  author       = {Henricsson, Fredrik and Ranebo, Ylva and Holm, E and Roos, P},
  issn         = {1879-1700},
  keyword      = {Bi-210,Po-210,Pb-210,Radiochemical analysis,Plating,Spontaneous,deposition},
  language     = {eng},
  number       = {5},
  pages        = {415--419},
  publisher    = {Elsevier},
  series       = {Journal of Environmental Radioactivity},
  title        = {Aspects on the analysis of (210)Po.},
  url          = {http://dx.doi.org/10.1016/j.jenvrad.2010.09.010},
  volume       = {102},
  year         = {2011},
}