AN-1418

Rapid Determination of226Ra in Water Samples

Summary of Method 226Ra is separated from up to 1 liter water samples and measured by alpha spectrometry.
Radium is precipitated from samples with calcium carbonate. The calcium carbonate precipitate is dissolved inhydrochloric acid, and cation exchange chromatography is used to purify radium and barium from matrix ions. Eichrom
DGA Resin is used to remove other alpha emitting nuclides from radium. Samples are prepared for radium
measurement by alpha spectrometry using barium sulfate micro-precipitation method onto Eichrom® Resolve Filters.
Sample preparation, including alpha spectrometry source preparation, for batches of 12-24 samples can be completed
by a single operator in as little as 3-4 hours. Yields can be traced with 133Ba by gamma spectrometry or 225Ra(229Th) byalpha spectrometry. If tracing with 225Ra, >8 hours of ingrowth time for the alpha emitting 217At daughter of 225Ra isrequired prior to measurement by alpha spectrometry.
Reagents
Cation Exchange Resin (Eichrom C8-B500-F-H)
DGA Resin, Normal 2mL Cartridges (Eichrom DN-R50-S)
Ammonium Hydroxide (listed as 28% NH3 or 56% NH4OH)
133Ba or 225Ra(229Th) Tracer
Nitric Acid (70%)
Hydrochloric Acid (37%)
1.25M Ca(NO3)2
2M Na2CO3
Barium Carrier (1mg/mL)
Isopropyl Alcohol
Ammonium Sulfate
Ascorbic Acid
Denatured Ethanol
Deionized Water
H2O2 (30%)

Equipment
Plastic Chromatography Column (Eichrom AC-50E-5M)
Column Extension Funnel (Eichrom AC-20X-20M)
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)
Resolve Filter in Disposable Funnel (Eichrom RF-DF-25-25PP01)
50mL and 250mL Centrifuge Tubes
Centrifuge
Stainless Steel Planchets with adhesive tapeHotplate
Alpha Spectrometry System
Gamma Spectrometry System (if 133Ba tracer used)
150mL Glass beakers
Vacuum Pump
Heat Lamp

Figure 1. Sample Preparation
Water sample+Tracer 133Ba or 225Ra(229Th)+10mL 56% NH4OH
Mix well.

Add 3mL 1.25M Ca(NO3)2 and10mL 2M Na2CO3. Mix well.**When minimizing reagent blank isimportant, a calcium phosphate ppt.
(AN1401) should be used.

Place in ice bath for 10 minutes.

Centrifuge 3500 rpm, 10 min

Dissolve precipitate in20mL 1.5M HCl and3mL 1.5M ascorbic acid.

Proceed to Column PurificationDecant
SupernateTo WasteFigure 2. Column Purification and Alpha Source Preparation(8) Add 50ug Ba carrier. Mix well.

(1) Prewash 5.0g 50Wx8
200-400 mesh, cationexchange resin column1:-10mL deionized water-20mL 6M HCl-10mL 0.5M HCl(9) Add 3g (NH4)2SO4 and 5mL isopropanol. Mix well.
(10) Place in ice bath for 30 minutes.

(2) Load Sample2(11) Set up Resolve® Filter Funnel
on vacuum box.

(3) Rinse 30mL 3M HCl(4) Add 2mL DGA cartridge below
cation exchange column.

(12) Wet filter with 3mL 80% ethanol
followed by 3mL DI water.

(5) Strip Ra/Ba with 25mL 5M HNO3.
(6) Add 2mL 30% H2O2.
Evaporate to dryness.
(7) Dissolve residue in
10mL 1.5M HCl.

226(18) Remove filter from funnel
assembly and mount filter on
stainless steel planchet withadhesive tape.

(13) Filter sample.
(14) Rinse sample
tube with 5mL
DI water andadd to filter.

(19) Dry filter under heat lamp for
3-5 minutes.
(20) Measure 226Ra and 225Ra(217At)
by alpha spectrometry after >8hours 217At ingrowth. (133Ba bygamma, if necessary.)(15) Rinse filter funnel
with 3mL DI water.
(16) Rinse filter funnel
with 1-2mL 100%ethanol.

Ra(17) 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
1234AVG
225

217

Ra( At)% Yield*
84.8
87.3
86.2
98.7
89 + 6226

226

Ra in Water

Ra(mBq/L)
Reference73.8
73.8
73.8
73.8
73.8

226

Ra(mBq/L)
Measured
69.6
75.7
71.3
66.9
70.9 + 3.7% Bias-5.7
2.6-3.4-9.3-3.9

229

Th in equilibrium with its daughters and* Ra tracer is added as
217
At daughter (7.066MeV) after
measured by its alpha emitting>8 hr ingrowth.

References1) Sherrod L. Maxwell, Brian K. Culligan, “Rapid Determination of 226Ra in Environmental Samples,” J. Radioanal.
Nucl. Chem., 293(1), 149-155 (2012).
1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

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