Measurement of 55Fe in Water(TEVA Separation)

AN-1611-10
Summary of Method 55Fe is separated and measured from up to 1L aliquots of water. Samples arepreconcentrated by evaporation or ferric hydroxide precipitation, dissolved in 4M HCl and loaded onto 2mL cartridges ofTEVA Resin. Hold back carriers, 2mg each of Zn, Mn, Cs, Nb, Zr, and Co are added to improve separation fromradionuclides of these elements. An iron phosphate precipitate at pH 2.8-3.2 is used to prepare samples for liquid
scintillation counting and remove remaining traces of Zn, which can co-elute with iron from TEVA resin. Chemical
recovery of iron is determined by ICP-AES measurement of 5mg of stable iron carrier. 55Fe may also be determinedusing TRU resin, AN-1612 from nitrate media. AN-1612 allows 55Fe incorporation into standard TEVA-TRU actinide
separations methods, but is limited to 2mg Fe per sample for a 2mL TRU resin cartridge.

Reagents
TEVA Resin Cartridges (Eichrom TE-R50-S)
Deionized Water
Sodium Hydroxide
HCl
HNO3
H3PO4
LSC 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 5 mg Fe, 2mg Zn, Mn, Cs, Nb, Zr, Co
Evaporate to dryness or proceed to ferrichydroxide precipitation 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 20mL 4M HCl.

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

Set up vacuum box with TEVA cartridges.
Precondition with 5mL 4M HCl.
Load samples on TEVA Resin.
Rinse tube with 5mL 4M HCl. Add to TEVA.
Rinse TEVA with 10mL 4M HCl.
Strip Fe from TEVA with 20mL 0.1M HNO3.
Add 5mL 1M H3PO4. Mix.
Adjust to pH 2.8-3.2 with NaOH/H3PO4. 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 pH100100Fe1L80% in precipitate% Fe Recovery

9896945mg FepH ~8-9
to limit
inclusionof alkaline
earth cations

92900500

Zn
60405mg Fe2mg Zn
50mL sample
5mmol H3PO4

2001000

1500

20000123456pHSample Volume, mL
Method Performance%Rec
2mg FeMethod Replicate tracer
TEVA
1
95.8
2
94.4
3
97.6
4
95.3
583.9
689.1
780.6
AVG
91.0
SD
6.6

Fe-55
Fe-55
raw %rec Tracer corrected
89.2
93.1
89.7
95.0
87.2
89.4
88.2
92.6
79.8
95.1
89.6
100.5
86.4
107.2
87.2
96.1
3.5
5.9

Bias-6.9
5.0
10.6
7.4
4.9-0.5-7.2

Impurity*<0.5%

References
1) ASTM Method D4922. “Standard Test Method for Determination of Radioactive Iron in Water.”

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