Reminder: accurate measurement of polonium in environmental samples is crucial because Po-210 is the main contributor to the natural radiation dose received by all living organisms. For the accurate determination of natural polonium concentration, Po-209 is added as an internal standard, and also as the yield determinant. Po(209+210) is deposited on silver planchets without an electrolyzer because the difference between the Po and Ag redox potential allows for spontaneous deposition.

Evaluating a commercially available dried milk formula, 3 samples of 10-gram each, were digested into 5 mL solutions. For the procedure yield control, also two 5-mL reference samples, containing no milk, were prepared. All five samples were handled in the same manner: each sample tube was spiked with 5 Bq of Po-209 tracer, and after a good shake and short reaction time, a thin silver planchet was immersed into each sample tube for the deposition of Po. After ~14h, the Po-coated planchets were removed, rinsed, and dried, then placed into the LSC counting vials and dissolved by adding a small amount of acid. When silver dissolved, LSC cocktail was added and samples were counted. On average, the alpha-activities of 256.5 dpm for the milk samples, and 225 dpm for the reference samples were measured. To find the content [Bq/g] of natural polonium in the milk formula, calculate:

a) difference between the measured activities of analyzed and reference samples is dpm

b) the overall yield % of the chemical procedure

c) activity of Po-210 in milk samples Bq/g