This is an indirect method. after six months you measure Polonium again. You use a formula to estimate the Pb-210. you can use any of the tracer (Po-209 or 208) to identify the recovery of the samples and to calculate the concentrations of Po-210

Yes, you must respike the sample. The best way is to do that: just after the first deposition, you leave silver inside the beaker for few days, to be sure that all the 210Po will be extracted. Then you close, wait for at least 6 months (even less) and then respike before the second extraction. You can have a look at the paper by Tom church and al, available on my page.

Another way to do is to use a different tracer at each extraction: 208Po and 209Po. But it is very difficult now to get 208Po standard.

The use of the tracer possible to estimate the remaining amount of polonium in the sample. And that amount of the remaining polonium can be used in the formula to estimate its contribution to the second count. Another way to reduce the amount of polonium remaining in the sample is increasing deposition time and control of deposition temperature (close to 80 ° C) to prevent emanation of polonium and reduce losses.

The problem of use a silver for few days is we assume that all polonium is extracted. the use of tracer allows estimating the remaining polonium and consider it in the formula.

Thanks for the info. I have been respiking but did not used to leave the planchet in sample solution after plating

Yes Olivier we are also using 209 Po standard

In the he sample add Po-209 tracer (1pCi) and do first electrodeposition of Po-210 and determine Po-210 using alpha spectrometry system. After the  210Po determination.   You leavea  silver planchet inside the beaker for few days, to ensure that all the 210Po along with Po-209 tracer are extracted. The you keep aside the solution for about  6 months.  Once again add Po-209 tracer (1pCi) and then second electrodeposition is carried out and 210Pb  was calculated.

• Thanks Kannan, Yep we do electrodeposition twice. the second time after 6 mo. But I will suggest dont leave teh disc inside beaker as you will have to count either side and this may take more time. We have designed a Planchet Holder that exposes a single surface only. We sell it at 50$ a piece. If you want please let us know. 

will you please tell me whether Po-210 electrodeposition on a single side will be 100%?.

Normally Po-210 electrodeposition on both sides accounts for about 100%.

I guess 100% (absolute) is not seen in either case 1 or 2 side but you can accout for efficiency easily. We have not seen any issue with teh coating efficiency. We make this is Teflon. It is patent pending. If you need a few we can get this to you without any charges.

I shall grateful if you can send me two or three planchet holders to my address given below:

Dr. V. Kannan

Scientific Consultant

National Centre for Sustainable Coastal Management

Government of India

Anna University Campus

Guindy, Chennai-600025

Tamilnadu State

India

At present I am planning to determine Po-210 in surface sediment sample in India.   Your device will be helpful in alpha counting using alpha spectrometry.

v.kannan