AN-1405

Rapid Determination of Sr in
Vegetation Samples

Summary of Method Strontium is separated and concentrated from 5-10 gram vegetation samples. Samples aremuffled in zirconium crucibles 2-4 hours to destroy organic content. The residue is wet ashed with HNO3-H2O2 and thenfused with 15g NaOH at 600°C for ten minutes. The fusion cakes are dissolved in water, transferred to 250mL
centrifuge tubes and precipitated with calcium phosphate to facilitate matrix removal. 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 ICP-AES measurement.
Average chemical recovery of strontium is 64 + 4% for 5g samples and 70 + 8% for 10g samples. Measured values of90Sr agreed to within 12% of reference values for 90 minute count times. The average time to complete the sample
preparation is <8 hours.
Reagents
Sr Resin, 2mL Cartridges (Eichrom SR-R50-S)
Sr Resin, 1mL Cartridges (Eichrom SR1ML-R50-S)
Nitric Acid (70%)
Hydrogen Peroxide (30%)
Deionized Water
Iron Carrier (50mg/mL Fe, as ferric nitrate)
Strontium Carrier (10mg/mL)
1.25M Ca(NO3)2
3.2M (NH4)2HPO4
2M Al(NO3)3
Sodium Hydroxide
90Sr standard
Oxalic acid

Figure 1. Sample Preparation
5-10g Vegetation sample in zirconium crucible
Muffle at 600°C.
2 hours for 5g sample.
4 hours for 10g sample.
Wet ash on hotplate with 5mL
70% HNO3 and 5mL 30% H2O2.
Fuse samples with 15g NaOH at
600oC for 10 minutes.

Equipment
Vacuum Box (Eichrom AR-24-BOX or AR-12-BOX)
Cartridge Reservoir, 20mL (Eichrom AR-200-RV20)
Inner Support Tubes-PE (Eichrom AR-1000-TUBE-PE)
Yellow Outer Tips (Eichrom AR-1000-OT)
50mL and 250mL Centrifuge Tubes
Centrifuge
Cupped Stainless Steel Planchets (~5mL volume)
Gas Flow Proportional Counter
Muffle Furnace
Hot Plate
Analytical Balance
250mL Zirconium crucibles with zirconium lids
Vacuum Pump

Dissolve fusion cake with H2O.
Transfer to 250mL centrifuge tube.
Add 125mg Fe and 4mg Sr. Dilute to 180mL.
Add 4mL 1.25M Ca(NO3)2, 5mL 3.2M (NH4)2HPO4.
Mix. Cool in ice bath for 10min.
Centrifuge at 3500rpm. Decant Supernate.
Dissolve precipitate in 5mL warm
3M HNO3, 7mL 70% HNO3, and7mL 2M Al(NO3)3.

Figure 2. Strontium Resin Separation (Optional 90Y Ingrowth)(1) Precondition Sr Resin with
10mL 8M HNO3.
(2) Load sample at 1-2mL/min.
(3) Rinse sample tube with 5mL
8M HNO3.
(4) Add tube rinse to Sr Resin.
Elute at 1-2mL/min.

Gas Flow Proportional Counting:**(Options for 89/90Sr Discrimination)(8) Evaporate samples to dryness
on tared cupped stainless steelplanchets.

(a) Sr fraction from step (7) can betransferred to a liquid scintillation vial.
89Sr can be measured by Cerenkov
counting (no LSC cocktail). 89/90Sr
can then be measured by adding
liquid scintillation cocktail.

(9) Rinse Sr sample vials with 2mL
0.05M HNO3. Transfer vial rinse toplanchets. Evaporate to dryness.

(5) Rinse Sr Resin sequentially with:(b) Sr fraction from step (10) can bedissolved in 10mL 8M HNO3 after >7days of 90Y ingrowth. 89/90Sr can beremoved on Sr Resin. 90Y will elute inSr Resin load and can be counted byliquid scintillation or gas flow
proportional counting.

- 15 mL 8M HNO3
- 10mL 3M HNO3 - 0.05 oxalic acid- 10mL 8M HNO3
(6) Dispose of (1) to (5) as waste.
(7) Strip Sr with 20mL 0.05M HNO3
at 1mL/min.
(10) Weigh planchets on an
analytical balance to determine
gravimetric yield of stable Sr(NO3)2.

2mL + 1mLSr Resin(11) Measure radiostrontium insamples on low background gas
flow proportional counter.

Cartridges*Actinides may also be measured by adding a 2mL TEVA, TRU and DGA cartridges above Sr Resin and following theseparation scheme in Eichrom application note AN-1406, “Rapid Determination of Actinides in Vegetation Samples.”90

Performance of Sr Method 5-10g Vegetation Samples
SampleReplicates
6SampleMass, g
5.0

2

10.0

2

10.0

90

Sr, Reference
Value (Bq/g)
0.255

90Sr, Measured
Value (Bq/g)
0.285 + 0.03% Bias
12Sr carrier% Recovery64 + 4

0.156

0.156 + 0.001

0.0

69 + 20.110

0.109 + 0.003-0.1

70 + 790 minute count times

References1) Sherrod L. Maxwell, Brian K. Culligan, Gary W. Noyes, “Rapid separation of actinides and radiostrontium invegetation samples,” J. Radioanal. Nucl. Chem., 286(1), 273-282 (2010).
1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

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