AN-1417-10

Rapid Determination of
226/228Ra in Water Samples

Summary of Method Ra isotopes are separated and measured from 1.0-1.5 liter samples of terrestrial waters.
Radium is concentrated from samples on MnO2 Resin. After a >36 hour ingrowth period for 228Ac from 228Ra, radiumand 228Ac are separated from matrix ions and potentially interfering radionuclides using stacked 2mL cartridges ofEichrom LN and DGA Resins. 228Ac is prepared for gas flow proportional counting using a cerium fluoride
microprecipitation onto Eichrom Resolve® Filters. 226Ra is prepared for alpha spectrometry using a barium sulfate
microprecipitation onto Eichrom Resolve® Filters. Chemical yield of radium is determined by adding either a 133Ba or225Ra(229Th) tracer. A single operator can process batches of 12-24 samples in 4-5 hours. Results for 226Ra and 228Ra
can be obtained in 48 hours, including >36 hour ingrowth time for 228Ac. Results for 226Ra and 228Ra in spiked river andground water samples typically agreed to within 5% of reference values. If tracing 226Ra with 225Ra(229Th) a minimum 8hour ingrowth time for the 217At daughter of 225Ra is required.
Reagents
MnO2 Resin (Eichrom MN-B100-A)
LN Resin (Eichrom LN-R50-S)
DGA Resin, Normal 2mL Cartridges (Eichrom DN-R50-S)
Ammonium Hydroxide (listed as 28% NH3 or 56% NH4OH)
133Ba or 225Ra(229Th) Tracer
Barium and Cerium Carriers (1mg/mL)
Nitric Acid (70%)
Hydrofluoric Acid (50%)
Hydrochloric Acid (37%)
Hydrogen Peroxide (30%)
1.25M Ca(NO3)2
Ammonium Sulfate
Denatured Ethanol
Isopropyl Alcohol
Deionized Water
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 Centrifuge Tubes
Stainless Steel Planchets with Adhesive Tape
Alpha Spectroscopy System
Gamma Spectroscopy System (if 133Ba tracer used)
Low Background Gas Flow Proportional Counter
150mL Glass beakers
Vacuum Pump
Hot Plate
Heat Lamp

Figure 1. Sample Preparation
1.0-1.5 Liter Water Samples
Adjust to pH2 with HNO3
+Tracer 133Ba or 225Ra(229Th)+1 mL 1.25M Ca(NO3)3

Adjust to pH 6-7 with NH4OH
1.5g column of MnO2 Resin, slurry
packed from water in 5mL column.
(Precondition column with 25mL DI water.)
Load sample at up to 15mL/min.
Rinse column with 50mL DI water.

Strip MnO2 with 12mL of 4M HCl-1.5% H2O2.
Bubbling will occur. Resin will turn from darkbrown to white as MnO2 is dissolved.
If measuring 228Ra, allow >36 hours
for 228Ac ingrowth.

Proceed to LN/DGA SeparationFigure 2. LN-DGA Separation and Alpha Source Preparation(1) Precondition LN + DGA
Resin with 5mL 4M HCl.
(2) Load samples at 1mL/min.
LN(3) Rinse sample tube
with 5mL 4M HCl.
(4) Add tube rinse to LN+ DGA Resin.
DGA(5) Rinse LN + DGA with5mL 4M HCl.
(6) Separate LN and DGA cartridges.

(12) 226Ra samples: Add 50ug Bacarrier. Mix well. Add 3g (NH4)2SO4.
Mix well. Add 5mL isopropanol. Placein ice bath for 30 minutes.
228Ra(Ac) samples: Add 50ug Cecarrier. Mix well. Add 1mL 49% HF.
Mix well. Wait 30 minutes.
(13) Set up Resolve® Filter Funnel
on vacuum box.

(14) Wet filter with 3mL 80% ethanol(7) Evaporate radium fraction fromfollowed by 3mL DI water.
steps (2) to (5) to dryness.
(8) Dissolve residue in 10mL of 0.1M (15) Filter sample.
HCl + 50uL 30% H2O2.
(16) Rinse sample
tube with 5mL(9) Pass Ra solution through same LN
DI water andresin cartridge (Ra not retained).
add to filter.
Rinse beaker with 5mL 0.1M HCl.
Add beaker rinse to LN resin.
(17) Rinse filter funnel
Collect load/rinse for step (12).
with 3mL DI water.
(18) Rinse filter funnel
with 1-2mL 100%ethanol.

(10) Rinse DGA Resin cartridge with15mL 4M HCl.
(11) Strip 228Ac from DGA with 10mL
of 0.5mL HCl.

133

Ba, 5.0pCi(22) Measure 228Ra(228Ac) by gas flow
proportional counting. Measure
226Ra and 225Ra(217At) by alpha
spectrometry after >8 hour 217At
ingrowth. (133Ba in 226Ra fraction
by gamma if necessary.)

Liters
1.51.0226

226/228

Ra in Water

133

Volume1040pCi(21) Dry filter under heat lamp for
3-5 minutes.

(19) Draw vacuum until filter is dry.

Method PerformanceSample
River Water
Ground Water(20) Remove filter from funnel
assembly and mount filter on
stainless steel planchet withadhesive tape.

Ba Tracer % Recovery % Recovery

Replicates
35Ra, 20pCi% Recovery
101 + 595 + 4226

Ra103 + 1
104 + 1228

Ra103 + 7102 + 8228

RaReferences
1) Sherrod L. Maxwell, “Rapid Method for 226Ra and 228Ra in Water Samples,” J. Radioanal. Nucl. Chem., 270(3), 651655 (2006).
1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

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