Measurement of 55Fe in Water(TRU Separation)

AN-1612-10
Summary of Method 55Fe is separated and measured from up to 500mL aliquots of water. Samples arepreconcentrated by evaporation or ferric hydroxide precipitation and purified on 2mL cartridges of TRU Resin. Holdback
carriers, 0.1-1mg each of Zn, Mn, Cs, Nb, Zr, and Co are added to improve separation from these nuclides of theseelements. An iron phosphate precipitate at is used to prepare samples for liquid scintillation counting. Chemical recoveryof iron is determined by ICP-AES measurement of 2mg of stable iron carrier. 55Fe may also be determined fromchloride media using TEVA resin (Eichrom AN-1611). AN-1612 provides higher Zn decontamination and can beincorporated into TEVA-TRU actinide separations, but is limited to 2mg total Fe per 2mL cartridge. AN-1611 can process
5-6mg of Fe, but is less rugged for Zn decontamination.

Reagents
TRU Resin Cartridges (Eichrom TE-R50-S)
Deionized Water
Sodium Hydroxide
HCl
HNO3
H3PO4LSC Cocktail
Fe, Zn, Mn, Cs, Nb, Zr, Co carriers (10mg/mL)
Phenolphthalein pH indicator
55Fe standard
Nitromethane or other LSC quench agent

Sample Preparation
Up to 1L of water sample in glass beaker.
Add 2mg Fe. 1mg Zn, Mn, Cs, Co. 0.1mg Nb, Zr .
Evaporate to dryness or proceed to Fe(OH)3 ppt
steps below.
Ferric Hydroxide Precipitation
Add pH indicator
Heat sample to 80oC
Adjust to pH 8-9 with NaOH.

Equipment
Vacuum Box (Eichrom AR-12-BOX or AR-24-BOX)
Vacuum Box Inner Liner (Eichrom AR-12-LINER orAR-24-LINER)
Yellow Outer Tips (Eichrom AR-1000-OT)
Inner Support Tube (Eichrom AR-1000-TUBE-PE)
Cartridge Reservoirs (Eichrom AR-200-RV20)
Centrifuge Tubes - 50mL and 250mL
20mL glass liquid scintillation tubes
Liquid scintillation counter
Calibrated pipets and disposable tips
Appropriately Sized Glass Beakers
ICP-AES system for Fe chemical yield measurement
Analytical balance
Vacuum Pump
Centrifuge
Hotplate

Mix sample and allow to cool to room temperature.
Allow ppt to settle and decant supernate to <200mL.
Transfer to 250mL centrifuge tube. Rinse beakerwith water to ensure complete transfer of ppt.
Centrifuge 10min. Decant supernate to waste.
Rinse ppt w/ 50mL Water. Centrifuge. Decant supernate.
Dissolve ppt/residue in 10mL 8M HNO3.

Iron Separation
1)
2)
3)
4)
5)
6)
7)
8)

Set up vacuum box with TRU cartridges.
Precondition with 5mL 8M HNO3.
Load samples on TRU Resin.
Rinse tube with 5mL 8M HNO3. Add to TRU.
Rinse TRU with 10mL 8M HNO3.
Strip Fe from TRU with 15mL 2M HNO3.
Add 5mL 1M H3PO4. Mix.
Adjust to pH 2.8-3.2 with NaOH. Mix.

9) Centrifuge. Decant Supernate.
10) Wash ppt with 50mL H2O. Centrifuge. Decant Supernate.
11) Dissolve ppt with minimal 6M HCl.
12) Transfer to 10mL volumetric flask. Dilute to 10mL.
13) Take 0.1-0.2 mL, dilute to 10mL for ICP-AES Fe yield.
14) Transfer balance of sample to 20mL glass LSC vial.
15) Add 6 drops H3PO4. Evap. on hotplate to ~0.5mL.
16) Add 1mL H2O. Cool. Add 15mL LSC cocktail. Mix.

Fe Recovery from Fe(OH)3 Precipitation

Precipitation Yield vs pH100100Fe500mL

80% in precipitate% Fe Recovery

9896942mg FepH ~8-9to limit
inclusionof alkaline
earth cations

92900200Zn
60405mg Fe2mg Zn
50mL sample
5mmol H3PO4200400600

8000123456pHSample Volume, mL

Method Performance%Rec2mg Fe
Method Replicate tracer
TRU
1
90.6
2
90.0
394.8
4
89.5
595.8
695.8
AVG
92.8
SD
3.0

Fe-55
Fe-55
raw %rec Tracer corrected
93.1
102.8
92.3
102.5
92.4
97.5
94.0
105.0
94.3
98.5
92.8
96.9
93.2
100.5
0.8
3.3

Bias
2.8
2.5
-2.5
5.0
-1.5
-3.1

Impurity*<0.5%References
1) Eichrom Method FEW01VBS. “Iron-55 in water,” http://www.eichrom.com/eichrom/radiochem/methods/eichrom/1955 University Lane Lisle, IL 60532, USA+1 (630)963-0320

www.eichrom.com

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