AN-1422

Rapid Determination of 226Ra
in 5g Vegetation Samples

226Ra is separated from 5 gram samples of vegetation and measured by alphaSummary of Method
spectrometry. Samples are fused with sodium hydroxide at 600°C. The fusion cake is dissolved in water, and radium isprecipitated from samples with calcium carbonate. The calcium carbonate precipitate is dissolved in hydrochloric acid,and cation exchange chromatography is used to purify radium and barium from matrix ions. Barium is removed fromsamples using Eichrom Sr Resin. Eichrom DGA Resin is used to separate other alpha emitting nuclides from radium.
Samples are prepared for alpha spectrometry by barium sulfate micro-precipitation onto Eichrom® Resolve Filters.
Sample preparation, including alpha spectrometry source preparation, for batches of 12 samples can be completed by asingle operator in as little as 6 hours. Yields are traced with 225Ra(229Th) by alpha spectrometry. At least 8 hours ofingrowth time for the alpha emitting 217At daughter of 225Ra is required prior to measurement by alpha spectrometry.

Reagents
Figure 1. Sample Preparation
Cation Exchange Resin (Eichrom C8-B500-F-H)
5g Vegetation +Tracer 225Ra(229Th) in Zr crucible
Sr Resin, 2mL Cartridges (Eichrom SR-R50-S)
DGA Resin, Normal 2mL Cartridges (Eichrom DN-R50-S)
Heat at 600°C in muffle furnace for 2 hours.
Nitric Acid (70%)
Hydrochloric Acid (37%)
225Ra(229Th) Tracer
Wet ash on hotplate with 5mL 70% HNO3 and 30% H2O2.
1.25M Ca(NO3)2
2M Na2CO3
Barium Carrier (1mg/mL)
Heat at 600°C in muffle furnace for 5-10 minutes.
Isopropyl Alcohol
Ammonium Sulfate
Denatured Ethanol
Ascorbic Acid
Add 10g NaOH.
Sodium Hydroxide
Hydrogen Peroxide (30%)
Fuse at 600°C in muffle furnace for 15 minutes.
Equipment
Remove from furnace. Cool 10 minutes.
Plastic Chromatography Column (Eichrom AC-50E-5M)
Dissolve fusion cake with 100mL DI water.
Column Extension Funnel (Eichrom AC-20X-20M)
Transfer to 250mL centrifuge tube. Add
Vacuum Box (Eichrom AR-24-BOX or AR-12-BOX)
10mL 37% HCl. Dilute to 150mL.
Cartridge Reservoir, 20mL (Eichrom AR-200-RV20)
Inner Support Tubes-PE (Eichrom AR-1000-TUBE-PE)
Add 0.5mL 1.25M Ca(NO3)2 andYellow Outer Tips (Eichrom AR-1000-OT)
10mL 2M Na2CO3. Mix well.
Resolve Filter in Disposable Funnel (Eichrom RF-DF-25-25PP01)
50mL and 250mL Centrifuge Tubes
Place in ice bath for 10 minutes.
Centrifuge
Stainless Steel Planchets with adhesive tapeDecant
Centrifuge 3500 rpm, 10 min
Hotplate
Supernate
Alpha Spectrometry System
Dissolve precipitate in 20mL 1.5M
To Waste
150mL Glass beakers
HCl and 3mL 1.5M ascorbic acid.
Vacuum Pump
250mL Zirconium Crucible w/ lid
Proceed to Column Purification
Muffle Furnace
Heat Lamp

Figure 2. Column Purification and Alpha Source Preparation(11) Add 50ug Ba carrier. Mix well.

(1) Prewash 5.0g 50Wx8
200-400 mesh, cationexchange resin column:-10mL deionized water-20mL 6M HCl-10mL 0.5M HCl(12) Add 3g (NH4)2SO4 and 5mL isopropanol. Mix well.
(13) Place in ice bath for 30 minutes.
(14) Set up Resolve® Filter Funnel
on vacuum box.

(2) Load Sample(3) Rinse 30mL 3M HCl(15) Wet filter with 3mL 80% ethanol
followed by 3mL DI water.

(4) Strip Ra/Ba with 25mL 5M HNO3.
(5) Add 2mL 30% H2O2.
Evaporate to dryness.
(6) Dissolve residue in 5mL
3M HNO3.
(7) Pass through 2mL Sr +DGA Resin Cartridges.
(8) Rinse Sr + DGA with
6mL 3M HNO3.
(9) Evaporate (7) +(8) to dryness.
226(10) Dissolve residuein 10mL 1.5MHCl.

(21) Remove filter from funnel
assembly and mount filter on
stainless steel planchet withadhesive tape.

(16) Filter sample.
(17) Rinse sample
tube with 5mL
DI water andadd to filter.

SrDGA(22) Dry filter under heat lamp for
3-5 minutes.
(23) Measure 226Ra and 225Ra(217At)
by alpha spectrometry after >8hours 217At ingrowth.

(18) Rinse filter funnel
with 3mL DI water.
(19) Rinse filter funnel
with 1-2mL 100%ethanol.

Ra(20) Draw vacuum until filter is dry.

1If using 133Ba tracer, 3.0g of cation exchange resin and proportionally smaller rinse volumes may be used.
2If tracing with 229Th, a 20mL 1M HCl-1M H3PO4 rinse following the sample load can improve purity of final 226Ra fraction.

Method Performance
225Sample**12345AVG217

Ra tracer is added asby its alpha emitting

Ra in 5g Vegetation Samples

226

Ra( At)% Yield*
91.5
88.3
93.1
82.2
80.2
87 + 6225*226

Ra(mBq/g)
Reference
73.8
73.8
73.8
73.8
73.8
73.8

226

Ra(mBq/g)
Measured
70.8
73.8
69.8
68.5
81.4
73 + 5% Bias-4.1
0.0-5.4
-7.2
10.3
-1.1

229

Th in equilibrium with its daughters and measured

217

At daughter (7.066MeV) after >8 hours ingrowth.

**5 grams of blank hay matrix spiked with226RaReferences1) Sherrod L. Maxwell, Brian K. Culligan, “Rapid Determination of 226Ra in Environmental Samples,” J. Radioanal.
Nucl. Chem., 293(1), 149-155 (2012).
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