Analytical Procedure

RADIUM IN WATER(CATION EXCHANGE AND LN RESIN)
1. SCOPE
1.1.

This is a method for the separation and measurement ofradium-226 and radium-228 in water. This method is meant to be
used in conjunction with Eichrom Method SPA01 for the rare earth
fluoride micro precipitation preparation of sources for 2 2 8 Ac ( 2 2 8 Ra)
analysis by gas flow proportional counting.

1.2.

This method does not address all aspects of safety, quality control,calibration or instrument set-up. However, enough detail is given
for a trained radiochemist to achieve accurate and precise results
for the analysis of the analyte(s) from the appropriate matrix, whenincorporating the appropriate agency or laboratory safety, quality
and laboratory control standards.

2. SUMMARY OF METHOD
2.1.

This test method is based on the utilization of solid phaseextraction of radium from water samples. The detection of the226
Ra is by alpha spectrometry and 2 2 8 Ra via 2 2 8 Ac by gas flow
proportional beta counter.

2.2.

An aliquot of the sample is measured into a beaker, and barium
carrier and 1 3 3 Ba are added. Radium and barium are sorbed on acation exchange column, eluted, evaporated to dryness, anddissolved in 0.095M HNO 3 . 2 2 8 Ac is selectively retained on acolumn of LN resin. 2 2 8 Ac is eluted with 0.35M HNO 3 , precipitatedwith rare earth fluoride, and collected on a resolve filter formeasurement by gas flow proportional counting. 2 2 6 Ra and 1 3 3 Ba
are collected from the LN load solution, precipitated with barium
sulfate, and collected on a resolve filter. 1 3 3 Ba is counted using agamma spectrometry while 2 2 6 Ra is counted via alphaspectrometry.

3. SIGNIFICANCE OF USE
3.1.

This is a rapid, reliable method for measurement of 2 2 6 Ra and 2 2 8 Ra
in water samples that is more cost-effective and efficient than
traditional ion exchange, solvent extraction and precipitation
techniques.

Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
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4. INTERFERENCES
4.1.

Potential beta emitters such as bismuth, yttrium and thorium would
be retained on the solid phase extraction resin column, while
eluting actinium from the resin.

4.2.

Interferences from other radioactive rare earth elements areeliminated under the stripping conditions of 0.35M HNO 3 .

4.3.

High levels of calcium can interfere with Ra sorption on the ion
exchange resin column and can cause excessive quantities ofprecipitate in the final barium sulfate micro precipitation step. For
samples containing less than 200 ppm, use 500 mL to 1 liter.
Sample size is limited to 100mL if the Ca content is greater than200 ppm but less than or equal to 500 ppm. The method has notbeen tested on samples containing greater than 500 ppm calcium.

4.4.

This method is suitable for the measurement of alpha emitting
radium isotopes and 2 2 8 Ra (via 2 2 8 Ac) from water samples. The
measurement of 2 2 8 Ac may be biased high if samples contain highlevels of 2 2 7 Ac (from 2 3 5 U decay chain) or fission products, such as
140Ba, 1 4 0 La, and Ce radionuclides. If measuring 2 2 8 Ra fromsamples potentially containing these interfering radionuclides, amethod isolating radium and then allowing for 2 2 8 Ac in-growthwould be more effective (Eichrom Method RAW01).

5. APPARATUS






Analytical balance, 0.0001 g sensitivity
Centrifuge tubes, 50mL
Column rack, Eichrom Part: AC-103
Extension funnels, 25 mL, Eichrom Part: AC-120
Flame burner
Fume hoodGamma spectrometry system
Hotplate
Ion exchange column, 1 to 1.5cm diameter column with 10mL of cationexchange resin, Eichrom Part: AC-20E-20M (column), Eichrom Part:
AC-20X-20M (funnel)
Low background gas flow proportional counter with appropriate sample
carriers and planchets
Petri dishes, plastic, 5-1/2 x 1 cm
Stir rods, glass
Vortex mixer

Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
Page 2 of 86. REAGENTS
Note: Analytical grade or ACS grade reagents recommended.
Ammonium sulfate,(NH4)2SO4
133

Ba tracer (~3000 dpm/mL)

Barium chloride dihydrate, BaCl2·2H2O
Cation exchange resin, hydrogen form, 100-200 mesh, Eichrom Part C8-B500-M-H
Deionized water, all reagents are prepared with deionized water
Hydrogen peroxide (30%), concentrated H2O2LN® resin, 2mL prepacked column, 100-150m, Eichrom Part LN-C50-ANitric acid (70%), concentrated HNO3
6.1.

Barium carrier (0.75 mg/mL)- Dissolve 0.34g BaCl 2 ·2H 2 O, in water.
Dilute to 250mL with water.

6.2.

Cerium carrier- Dissolve 0.155g cerium nitrate hexahydrate in50mL water. Dilute to 100 mL with water.

6.3.

Ethanol, 80%- Add 80 mL denatured ethanol to 20 mL water.

6.4.

Nitric acid solution (0.095M)- Add 5.9 mL of concentrated HNO 3 to
900mL of water. Dilute to 1L with water.

6.5.

Nitric acid solution (0.35M)- Add 22mL of concentrated HNO 3 to800mL of water. Dilute to 1L with water.

6.6.

Nitric acid solution (0.1M)- Add 6.3 mL of concentrated HNO 3 to800 mL of water. Dilute to 1L with water.

6.7.

Nitric acid solution (8M)- Add 500 mL of concentrated HNO 3 to 400
mL of water. Dilute to 1L with water.

7. PROCEDURE
7.1.

Water Sample Preparation:

7.1.1. If required, filter the sample through a 0.45 micron filter.
7.1.2. Aliquot 500 to 1000mL of the sample (or enough to meetrequired detection limit) into an appropriate size beaker. Add anappropriate amount of 1 3 3 Ba tracer.
Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
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7.1.3. Acidify sample with nitric acid to pH 2, if necessary.
7.1.4. Prepare a cation exchange column containing 10 mL of cationexchange resin.
7.1.5. Precondition the column with 50mL of 0.1M HNO 3 .
7.1.6. Pass the sample through the column at the rate of not morethan 5 mL/min.
7.1.7. Rinse the column with 25mL of 0.1M HNO 3 .
7.1.8. Properly dispose of the feed and rinse.
7.1.9. Elute radium, barium, and 2 2 8 Ac (and other cations) with 100mLof 8M HNO 3 into a 250mL beaker.
7.1.10. Evaporate the eluate completely to dryness on a hot plate in afume hood.
Note: The effectiveness of the subsequent radium/228Ac separation on LN resin is dependent on
the concentration of HNO3 in the solution prepared in step 7.1.10. Traces of HNO3 remaining
from the evaporation step 7.1.10. can prevent the uptake of 228Ac by LN resin. Ensurecomplete evaporation of all HNO3 in step 7.1.10.
7.1.11. Dissolve the residue in 10mL of 0.095 M HNO 3 . If necessary,
cover with a watch glass and heat gently. Check that pH is ~1.
Adjust to pH 1 as necessary.
7.2.

Ac-228 Separation Using LN Resin:

7.2.1. Prepare an LN Resin column for each sample by removing thebottom plug and the cap. Place each column in the column rackwith a waste reservoir below the columns. Press each top fritdown snugly to the resin surface using a glass rod (orequivalent) and let the solution drain out.
7.2.2. Add 5mL of 0.095 M HNO 3 to precondition each column. Allow
the solution to drain by gravity.
7.2.3. Place a clean, labeled 50mL polypropylene centrifuge tube
under each column to collect radium and barium.
7.2.4. Transfer each sample solution to the appropriate column
reservoir. Allow the solution to drain by gravity. 2 2 8 Ac will be
retained on the LN column, while radium and barium elute into
the centrifuge tube.
Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
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7.2.5. Rinse the sample beakers with 5mL of 0.095M HNO 3 . Add therinse to the appropriate column. Record the time and date ofthis rinse. This will be the separation of 2 2 8 Ac from 2 2 8 Ra.
Collect the eluate for 2 2 6 Ra and barium.
7.2.6. Rinse the column with 5 mL of 0.095M HNO 3 and collect theeluate for 2 2 6 Ra and barium.
7.2.7. Set the combined eluate from steps 7.2.4. to 7.2.6. aside forsource preparation for the measurement of radium and barium.
7.2.8. Place a clean, labeled tube under each column. Elute 2 2 8 Ac with10 mL of 0.35M HNO 3 into a plastic centrifuge tube.
Note: 228Ac has a 6.13 hour half‐life. The following steps for the determination of 228Ac must be
performed quickly.
7.2.9. Prepare sources for the determination of 2 2 8 Ac using rare earth
fluoride micro precipitation (Eichrom Method SPA-01).
7.2.10. Measure 2 2 8 Ac using a low background gas flow proportionalcounter.
7.3.

Barium sulfate micro-precipitation for 2 2 6 Ra

7.3.1. Count the eluate from step 7.2.7. for 1 3 3 Ba on a Gamma counterfor tracer recovery.
7.3.2. Add 3.0g of ammonium sulfate to the combined eluate fromsteps 7.2.7. Mix to dissolve.
7.3.3. Add 100L of barium carrier to each sample. Swirl to mix.
7.3.4. Add 5mL of isopropanol to each sample. Swirl to mix.
7.3.5. Place tubes in an ice- water bath for at least 30 minutes.
7.3.6. Prepare alpha spectrometry sources on resolve filters as
outlined in Eichrom Method SPA01, steps 5.4. to 5.15.
7.3.7. Count samples by alpha spectrometry.
8. CALCULATIONS
Calculate 228Ra activity:(To convert pCi/L to Bq/L, multiply by 0.037):

Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
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A228

Ra (pCi/L) =2.22  E  V  Y  e


-t1

t 2
1  e  t 2

where:AE
YVt1
t2



= net count rate, cpm= counting efficiency expressed as fraction= 133Ba (Ra) yield expressed as fraction= Sample volume (liters)= decay time of 228Ac, from start of rinse until start of counting(minutes)= counting time (minutes)= decay constant of 228Ac (1.88*10-3 min-1)

Calculation for Ra-226 activity(To convert pCi/L to Bq/L, multiply by 0.037):
226

Ra (pCi/L) =SB
2.22.  E  Y  V

where:
S = sample counts per minute
B = background counts per minuteE = efficiency of counter
V = volume of samples in liters
Y = Barium-133 yield

Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
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9. PERFORMANCE DATA
9.1.

This method has been used to analyze various intercomparison
and reference samples supplied by external organizations.
Chemical recovery and agreement with reference values wasexcellent. (To convert pCi/L to Bq/L multiply the value by 0.037,
therefore 1.41 pCi/L = 0.052 Bq/L or 2 mBq/L.) Data below wasgenerated from 500 mL samples of drinking water samples
supplied as indicated. For more details, contact Eichrom:
Chemical Yield(133Ba)

Eichrom Result(226Ra - pCi/L)

Reference Value(226Ra - pCi/L)

US EPA (9/18/98)

96%

1.41  0.17

1.7  0.5

New Jersey State Lab

91%

8.64  1

9.1  0.5

Georgia Tech (S8933)

88%22.6  3.0

18.0  2.0

Georgia Tech(WS14776)

88%

4.14  0.58

3.3  0.3

10. REFERENCES

1) Burnett, W.C., P.H. Cable, and Russ Moser, “Determination of Radium-228 in
Natural Waters Using Extraction Chromatographic Resins,” Radioactivity &Radiochemistry, Vol. 6, No. 3, pp. 36-43 (1995).
2) Maxwell, S.L., et al., “Rapid method for determination of 228Ra in water
samples,” J. Radioanal. Nucl. Chem. 295, 2181-2188, (2013).
3) Maxwell, S.L., et al., “Rapid method for determination of 226Ra in urinesamples,” J. Radioanal. Nucl. Chem. 300, 1159-1166 (2014).

Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
Page 7 of 8

Eichrom Technologies, LLC
Analytical Procedure
May 1, 2014

Method No: RAW03
Revision: 1.4
Page 8 of 8