Rapid Method for Sodium Carbonate Fusion of Soil and Soil-Related Matrices Prior to Strontium-90 Analyses for Environmental Remediation Following Radiological Incidents

September 2013 TJndate: EPA has validated and published a rapid method for sodium carbonate fusion of soil
matrices for analysis of strontium-90. The method is summarized and accessible through the link
provided below, and replaces use of the Department of Energy's "Actinide and Sr-89/90 in Soil Samples"
for analysis of strontium-90 in soil using the methods listed in SAM.
Rapid Method for Sodium Carbonate Fusion of Soil and Soil-Related Matrices Prior to
Strontium-90 Analyses for Environmental Remediation Following Radiological Incidents
Analyte(s)
CAS RN
Strontium-90
10098-97-2
Analysis Purpose: Qualitative analysis
Technique: Beta counting
Method Developed for: Strontium-90 in soil samples
Method Selected for: SAM lists this method for qualitative analysis of soil/sediment samples
Description of Method: The method is based on the complete fusion of a representative, finely ground
1-g aliquot of dried sample with no insoluble residue remaining after dissolution of the fused melt in acid.
For media composed of organic soil, the sample is dry-ashed at 600 °C in an appropriate vessel prior to
fusion. The sample is dissolved in a crucible with hydrofluoric acid and evaporated to dryness on a
hotplate at medium to high heat (-300 °C). Dry flux mix (equal weight of dried sodium carbonate,
potassium carbonate and boric acid) is added and the crucible is warmed under a flame until a reaction
initiates. The crucible is then heated under full flame until the reaction subsides and the melt is
completely liquid and homogeneous. After cooling, the solidified melt is dissolved in nitric acid. A
calcium solution and phenolphthalein indicator is added to this mixture and the pH is adjusted to 8.3 with
sodium hydroxide. The sample will become pinkish-orange due to the indicator color change and the
formation of hydroxide precipitate. Sodium carbonate and heat is added to bring the precipitation to
completion. After cooling and allowing the precipitate to settle, the supernatant is decanted and the
precipitate is transferred to a centrifuge tube and dissolved in nitric acid. The sample is then processed for
Strontium-90 determination using Rapid Radiochemical Method for Total Radiostrontium (Sr-90) in
Water for Environmental Restoration Following Homeland Security Events (http://www2.epa. gov/
radiation/rapid-radiochemical-methods-selected-radionuclides).
Special Considerations: If the sample may contain discrete radioactive particles (DRPs) or particles
larger than a nominal size of 150 (mi, additional sample preparation may be necessary as described in
Sections A4 and A5.2.3 of the method (Interferences and Hot Particles, respectively). Soils with high
silica content may require either additional fusing reagent and boric acid or a longer fusion melt.
Platinum crucibles must be used in this method, when digesting samples with hydrofluoric acid. If
platinum crucibles are not available, an effective, alternate method is available that uses zirconium
crucibles [see Rapid Method for Sodium Hydroxide Fusion of Concrete Matrices prior to Am, Pu, Sr.
Ra, and U Analyses (www2.epa.gov/radiation/incident-guides) and Rapid Radiochemical Method for
Total Radiostrontium (Sr-90) in Building Materials for Environmental Remediation Following
Radiological Incidents (www2.epa.gov/radiation/incident-guides)l.
Source: EPA, National Air and Radiation Environmental Laboratory (NAREL). August 2012. Rev 0.
"Rapid Method for Sodium Carbonate Fusion of Soil and Soil-Related Matrices Prior to Strontium-90
Analyses for Environmental Remediation Following Radiological Incidents," EPA-600-R-12-640.
http://www2.epa.gov/radiation/rapid-radiochemical-methods-selected-radionuclides
U.S. Environmental Protection Agency
Office of Research and Development, Homeland Security Research Program
EPA/600/S-13/227
September 2013

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