Rapid Determination of Sr in Emergency Milk Samples
Published Time：2016-12-08
Summary of Method
Strontium is separated and concentrated from 100mL milk samples using a calcium phosphate precipitation. The precipitate is dissolved with nitric acid and centrifuged to remove residual protein and fat.
The supernate, containing Sr, is wet ashed with HNO3-H2O2 and then heated in a muffle furnace at 550°C for 30-60
minutes to destroy any residual organic matter. The muffled residue is wet ashed again with HNO3-H2O2 and dissolved
in HNO3-Al(NO3)3. Strontium is separated from matrix impurities and potentially interfering radionuclides in the sample
using stacked 2mL and 1mL cartridges of Eichrom Sr Resin. Radiostrontium is measured on a low background gas flow
proportional counter or liquid scintillation counter. Chemical yield of strontium is determined by gravimetric recovery of
stable strontium or by ICP-AES measurement. Average chemical recovery of strontium is 75 + 17%. Measured values
of 90Sr agreed to within 3.2% and 0.5% of reference values for 20 minute count times and 60 minute count times,
respectively. The lower limit of detection for 100mL samples with 20 minute count times is 0.5Bq/L and with 60 minute
count times is 0.16Bq/L. A single operator can prepare batches of 12-24 samples for 90Sr measurement in less than
8 hours.
