Determination of 227Ac inWater Samples

AN-1602-10
Summary of Method 227Ac is preconcentrated from up to 1L of water sample using a ferric hydroxide precipitation.
Following dissolution in 4M HCl, 227Ac is separated from radiometric impurities using a 2mL cartridge of DGA, Normalresin. 227Ac is prepared for measurement using a CeF3 microprecipitation onto Resolve(R) Filters. An 225Ac(229Th) tracer isused to measure chemical recovery of actinium. After a 30 minute ingrowth time, the 225Ac tracer yield is measured via
alpha spectrometry. 227Ac is measured via its 227Th and 223Ra daughters after a longer period of ingrowth (30-90 days).
Actinium yields are typically 70-90%. MDA for 227Ac was 0.05Bq/L for 3 day count times after 90 days ingrowth period.

Reagents
DGA Resin, 2mL Cartridges (Eichrom DN-R50-S)
Iron Carrier (50mg/mL Fe, as ferric nitrate)
Cerium Carrier (10mg/mL)
229Th(225Ac) tracer
Hydrofluoric Acid (49%) or Sodium Fluoride
Nitric Acid (70%)
Hydrochloric Acid (37%)
Sodium Hydroxide
Deionized Water
H2O2 (30%)
Optional for additional Th/U removal:
TRU Resin, 2mL cartridges (Eichrom TR-R50-S)

Sample Preparation
Up to 1L Sample

Aliquot Sample. Add 229Th(225Ac) tracer
and 25 mg of Fe carrier.

Heat sample to 80oC and mix well toequilibrate sample and tracer.
Adjust pH to 8-9 with NaOH.

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)
Resolve Filters in Funnel (Eichrom RF-DF25-25PP01)
50mL and 250mL Centrifuge Tubes
Alpha Spectrometry SystemCentrifuge
Vacuum Pump
Heat Lamp
Analytical Balance
Hot Plate
1L Glass beakers
pH meter or pH strips or pH indicator (pH 8-9)

Cool sample and allow ppt to settle.
Decant supernate to ~200mL.
Transfer sample to 250mL centrifuge tube.
Centrifuge 2500 rpm for 10 minutes.
Decant Supernate.
Rinse ppt with 50mL water. Centrifuge.
Decant Supernate.
Dissolve precipitate with 10mL conc. HCl.
Dilute to 30mL.

Ac Separation on DGA(1) Precondition 2mL DGA
with 10mL 4M HCl.*(2) Load sample solution.

DGA(3) Rinse sample tube with5mL 4M HCl. Add tube
rinse to DGA. (If TRU
cartridge is used, remove
following this step.)(4) Rinse DGA with 10mL 3M HNO3.
(5) Rinse DGA with 20mL 0.5M
HNO3.

(7) Add 0.5mL 30% H2O2 to samples.
(8) Add 50ug Ce carrier to samples.
Mix well. Add 1mL 49% HF.
Mix well. Wait 15-20 minutes.
(9) Set up Resolve® Filter Funnel onvacuum box.
(10) Wet filter with 3mL 80% ethanol
followed by 3mL DI water.
(11) Filter sample.
(12) Rinse sample tube with 5mL DIwater and add to filter.

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

(6) Strip Ac from DGA with
20mL 2M HCl. (2M HCl is used
to achieve additional
decontamination from Th.)

* A 2mL cartridge of TRU resin may
be added above DGA for additional
decontamination from U/Th.

(14) Draw vacuum until filter is dry.
(15) Remove filter from funnel
assembly and mount filter on
stainless steel planchet with 2sided tape.

(17) Measure actinides by alpha
spectrometry.

(13) Rinse filter funnel with 3mL DI
water and 2mL 100% ethanol.

Method Performance
227

WaterStandard
IAEA
Standard

227

Ac
Measured
Bq/kg

AcReference
Bq/kg% BiasTracerRecovery333 + 16329 + 16

1.275References
1) H. Dulaiova, K.W.W. Sims, M.A. Charette, J. Prytulak, J.S. Blusztajn “A new method for the determination ofactinium-227 in geological samples,” J. Radioanal. Nucl. Chem., 296, 279-283 (2013).
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