Determination of 225Ac inWater Samples

AN-2101
Summary of Method 225Ac (t1/2 = 10 days) is preconcentrated from up to 1L of water sample using a ferrichydroxide precipitation. Following dissolution in 4M HCl, 225Ac is separated from radiometric impurities using 2mL
cartridges of TRU and DGA, Normal resin. 225Ac is prepared for measurement using a LaF3 or CeF3 microprecipitation
onto Resolve(R) Filters.
Chemical recovery of actinium can be traced using 227Ac (alpha spectrometry) or stable La (ICP-MS or ICP-AES).
225Ac may be measured by alpha spectrometry (5.54-5.83 MeV) or gamma spectrometry (via its 221Fr daughter, 218 keV,11.44%).
The alpha emission from 227Ac tracer (4.71-4.90 MeV) only occurs in 1.38% of decays. Therefore, use of 227Ac tracer
may be more efficient by measuring its 227Th (5.59-6.04 MeV) or 223Ra (5.24-5.87 MeV) daughters after a period ofingrowth and decay of 225Ac.
The mass of La that can be added to use a yield tracer must be minimized (55 g) to prevent degradation of thealpha spectra through self-absorption. However, this amount of La should be sufficient to measure via ICP-MS orReagents
DGA Resin, 2 mL Cartridges (Eichrom DN-R50-S)
TRU Resin, 2 mL cartridges (Eichrom TR-R50-S)
Iron Carrier (50 mg/mL Fe, as ferric nitrate)
Cerium Carrier (10 mg/mL)
227Ac tracer or Lanthanum Carrier (10 mg/mL)
Hydrofluoric Acid (49%) or Sodium Fluoride
Nitric Acid (70%)
Hydrochloric Acid (37%)
Sodium Hydroxide
Deionized Water
H2O2 (30%)
Equipment
Vacuum Box (Eichrom AR-24-BOX or AR-12-BOX)
Cartridge Reservoir, 20 mL (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)
50 mL and 250 mL 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)

Sample Preparation
Up to 1L Sample

Aliquot Sample. Add tracer (227Ac or 55 g La)
and 25 mg of Fe carrier.
Heat sample to 80oC and mix well toequilibrate sample and tracer.
Adjust pH to 8-9 with NaOH.
Cool sample and allow ppt to settle.
Decant supernate to ~200 mL.
Transfer sample to 250 mL centrifuge tube.
Centrifuge 2500 rpm for 10 minutes.
Decant Supernate.
Rinse ppt with 50 mL water. Centrifuge.
Decant Supernate.
Dissolve precipitate with 10mL conc. HNO3.
Dilute to 25 mL.

Ac Separation on TRU-DGA(1) Precondition 2mL TRU andDGA with 10mL 6M HNO3.
TRU(2) Load sample solution.
(3) Rinse sample tube with
5mL 6M HNO3. Add tube
rinse to TRU-DGA.
DGA(4) Rinse TRU-DGA with 10mL
3M HNO3.

(5) Rinse TRU-DGA with 15mL 2M
HCl (transfers La/Ac to DGA).
(6) Discard TRU. Rinse DGA with
20mL 0.5M HNO3.
(7) Strip Ac from DGA with
20 mL 2M HCl. (2M HCl is usedto achieve additional
decontamination from Th.)
*If using stable La as the yield tracer,
remove 2 mL aliquot and dilute to
10 mL for recovery measurement byICP-MS or ICP-AES.

(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.

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

(14) Draw vacuum until filter is dry.
(15) Remove filter from funnel
assembly and mount filter on
stainless steel planchet with**If stable La is used as the yield tracer,2-sided tape.
omit the addition of 50 ug of Ce.
The La will serve as the carrier forthe rare earth fluoride micro-ppt.

(9) Set up Resolve® Filter Funnel on
vacuum box.
(10) Wet filter with 3mL 80% ethanol
followed by
3mL DI water.

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

(11) Filter sample.
(12) Rinse sample
tube with 5mL
DI water andadd to filter.

(17) Measure actinides by alpha
spectrometry.

References
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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