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NBS TECHNICAL NOTE 1137

V 1 y

NATL INST OF STAND & TECH

A111D7 ED=^3flfl

U.S. DEPARTMENT OF COMMERCE/ National Bureau of Standards

QC

100

.U5753

NO. 1137

1981

C.2

Evaluation of Methods

For the Assay of

Radium-228 in Water
NATIONAL BUREAU OF STANDARDS

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National Bureau of Standards

Library. E-Ol Admin. Bidg.

MAR 1 6 1981

Evaluation of Methods For the Assay of aioo

Radium-228 in Water

-^"^

J. R. Noyce

Center for Radiation Research

National Measurement Laboratory

National Bureau of Standards

Washington, DC 20234

Sponsored by: Quality Assurance Division Environmental Monitoring Systems Laboratory

U.S. Environmental Protection Agency. P.O. Box 15027 Las Vegas. NV 89114

^^^»*' °^ OO.

f f C

|--) f^ f 0^ I f), rylf

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

U . ^, NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued February 1981
National Bureau of Standards Technical Note 1137

NaL Bur. Stand. (U.S.), Tech. Note 1137, 18 pages (Feb. 1981) CODEN; NBTNAL

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1980

For sale by the Superintendent of Documents, U.S. Government Printing Office. Washington. D.C. 20402

Price Si. 50 (Add 25 percent for other than U.S. mailing)
EVALUATION OF METHODS FOR THE ASSAY OF RADIUM-228 IN WATER

by

J. R. Noyce

The technical literature from 1967 to May 1980 was searched for methods for

assaying radium-228 in water. These methods were evaluated for their

suitability as potential EPA reference methods for drinking water assays.

We suggest the present EPA reference method (Krieger, 1976) be retained

but improved, and a second method (McCurdy and Mellor, 1979), which

empl oys 3 -Y coincidence counting, be added. Included in this report is

a table that lists the principal features of 17 methods for radium-228

assays.

Keywords: Analysis; assay; evaluation; radioactivity; radiochemistry

;

radium-228; reference method; water.

Introduction

Radium-228 is a radionuclide hazardous to human health because, like

radium-226, it is incorporated into the skeleton and has a long biological residence time. Radium-228 is ingested primarily by the drinking of water. It has been found to occur in higher concentrations than

^^^Ra in water in contact with some geologic formations in the United States

(Johnson, 1971; Michel and Moore, 1980) and in Brazil (Hainberger, 1974).

Radium-228 is difficult to assay accurately, especially at low concentrations, because it emits only very low-energy conversion electrons

(less than 6 keV) and low-energy beta particles (10 keV average energy).

Other isotopes of radium or their daughters cannot readily be added to

samples as tracers for measuring the chemical yields of assays because:

1) they are also likely to be present in the water, particularly 224p3

and 22^Ra, or 2) they are themselves inconvenient to prepare and assay,

as in the cases of ^^^Ra and ^^^Ra.

-1-
The U. S. Environmental Protection Agency has regulations which set limits

on the concentrations of radionuclides, including ^^"Ra, in drinking water

(EPA, 1976), and which specify approved assay methods. The EPA reference

method for ^^^Ra (Krieger, 1976) is based on a U.S. Geological Survey

method (Johnson, 1971), which was also recommended by the World Health

Organization (Lund, 1976). In addition, the U.S. Food and Drug Administration (FDA, 1979) has regulations pertaining to radionuclides in

bottled water, modelled on the EPA regulations. Other methods for the

low-level assay of ^2°Ra are available, but each of them, as well as the

present reference method, has one or more deficiencies for use in monitoring.

All assay methods for radionuclides should have sufficient and demonstrated

precision, accuracy, and sensitivity to meet the purposes of the assay.

With the possible exception of simple screening tests, such as "gross a"

measurements, all radiochemical methods also should incorporate steps for

determining the chemical yield.

There are additional desirable features that should be present in an ideal

monitoring method. The method should be "rugged", which means it will perform well under less than ideal conditions. It should provide results

without requiring a long wait for the ingrowth or decay of a radionuclide,

and it should be suitable for use with large numbers of samples; that is,

it should have relatively low labor and supply costs.

The Quality Assurance Division in the Environmental Monitoring Systems

Laboratory of the EPA, Las Vegas, requested the NBS Radioactivity Group,

Nuclear Radiation Division, to survey the literature for ^^^Ra assay methods

and evaluate their suitability as potential EPA reference methods.

-2-
Survey of Literature

Nuclear Science Abstracts was searched from 1967 until its termination in

1977. Then, the Energy Data Base was searched from 1977 through

May 1980. Also, Chemical Abstracts was searched from 1968 through May 1980.

References cited in the relevant papers found in these searches led to

other papers dating from approximately 1960.

There are only a few papers giving methods for assaying ^^°Ra in water

and the results of such measurements. Many of the available papers deal

with seawater rather than fresh water. The pertinent aspects of the

methods are set forth in Table 1 in alphabetical order of author.

Some of these publications also deal with ^^^Ra assays, and salient features

of these methods are included in Table 1. Papers concerned only with 226pg

assays are not included.

Also in Table 1 are ^^^Ra assay procedures found during the search

that are for other types of samples, such as soil. The latter methods

usually can be adapted to the assay of water samples, and some contain useful

techniques not exploited in the water-assay procedures. Reports of

investigations using previously published 228^^ assay procedures are excluded.

Evaluation of Methods

Most of the following discussion further explains important points made in

Table 1. Nearly all the assay methods separate and purify ^^°Ac and count

beta particles emitted in its decay. The method of McCurdy and Mellor (1979)

is unique in that the 228/\(. -jg pQ-j- separated from its 228pg parent for counting. Thus, 2^^Ac can be counted as long as desired or recounted days later

-3-
without performing additional radiochemistry on the sample. A few procedures

use the detection of radiations emitted by later members in the ^^°l\c decay

series, including 228j|^^ 224pg^ 3^^ gyg^ 212p[3 f^Q^ de-emanated ^^^Rn. Only

the method of Tomza (1977) uses liquid-scintillation counting.

The assay methods listed in Table 1 appear to have the sensitivity required

by the EPA drinking water regulations (EPA, 1976), with the apparent exceptions of those of Iyer et al . (1966) and Baretta and Feldman (1961). There

is some evidence that at low ^^^Ra concentrations a method for counting

alpha particles from the decay of 2^°Th has better precision than one for

counting beta particles from the decay of ^28/^^ (Knauss et al . , 1978), but

the time required for 228jh ingrowth is much longer than that for ^^^Ac.

The methods in Table 1 lacking a provision for determining the chemical

yield for each sample processed are those of Humphrey et al . (1975),

Johns et al . (1979), Kuchta et al . (1976), MacKenzie et al . (1979), Percival

and Martin (1974), Petrow et al . (1964), Sakanoue et a1 . (1973), and Tomza

(1977). This is also true of procedures of Barratta and Feldman (1961), and

of Kahlos and Asikainen (1973), but both could readily be modified for

gravimetric determination of chemical yields. Some of the methods which

do provide a chemical yield, however, require long waiting times (see below).

Four of the methods use radioactive tracers to measure chemical yields:

Kaufman et al . (1973), Koide and Bruland (1975), Michel and Moore (1980), and

Smith and Mercer (1970). Because the present EPA reference methods for radionuclides other than tritium do not require radioactive tracers (Krieger, 1976),

it was assumed they are to be avoided when another yield-measuring technique

-4-
is available. It should be noted that the chemical yield is incorrectly

calculated in the reference method for 228pa (Krieger, 1976). Any loss of

sample in steps 13 and 14 is counted twice. The Ba(Ra)S04 precipitate

at the end of step 11 should be weighed, rather than in step 25 as stated.

The waiting periods in the methods given in Table 1 for ingrowth or decay

of radionuclides during an assay can be divided into three groups:

less than two full days, two days to 30 days, and greater than 30 days.

Waiting periods include time for the ingrowth of ^^^Rn for those procedures

where assays of ^^"Ra are an integral part of the ^^°Ra assays. The shorttime procedures in the first group are Raratta and Feldman (1961), Humphrey

et al . (1975), Iyer et al . (1966), Krieger (1976), McCurdy and Mellor

(1979), Percival and Martin (1974), and Petrow et al . (1964). Methods

with waiting periods of between two and 30 days are Johns et al . (1979),

Kahlos and Asikainen (1973), Koide and Bruland (1975), and Smith and

Mercer (1970) ( via ^^^Ac). Methods requiring waiting times of longer than

30 days are Kaufman et al . (1973), Kuchta et al . (1976), MacKenzie et al .

(1979), Michel and Moore (1980), Sakanoue et al . (1973), Smith and Mercer

(1970) (via228Th)^ and Tomza (1977).

The methods of Kuchta et al . (1976) and Tomza (1977) would have waiting

times of only two to 30 days if ^^'^Ra were known to be in equilibrium

with 22^Ra, but this condition would probably be rare for drinking

water. Finally, the waiting period in the procedure of MacKenzie et al .

(1979) could also be reduced to between two and 30 days if the more

volatile beta-particle-emitting progeny of ^^^Ac could be flamed off a

-5-
source evaporated on a stainless steel planchet with no accompanying loss

of 228^(, (compare with Koide and Rruland (1975)).

A potential problem confronting the methods which assay 2^°Pa via "^"^^kc

is the presence of radioisotopes of the rare-earth elements or those with

similar chemical properties, especially ^^Y, daughter of '^^Sr. Some of

the procedures have one or more steps designed to reduce such contamination,

and the 6- Y coincidence counting technique of McCurdy and Mellor (1979) is

not affected by ^'-'y. A recent interlaboratory assay exercise, with a water

test sample that had ^^Sr-^'-'Y added, indicated that the present EPA reference

method does not adequately remove ^'-'y from ^^"Ac (Whittaker, 1980).

The Y or La compound chosen as the carrier for Ac should be checked for

radiochemical purity before use, because it may be a significant source of

beta activity (Johnson, 1971). Such a warning should be added to the

reference method.

It is difficult to assess the "ruggedness" of an analytical method from just

a literature survey. In general, the less complex an assay procedure is, the

better chance of its being "rugged". However, some of the simpler procedures

in Table 1 cire without a means for measuring chemical yields.

The "special apparatus" columns in the table list items needed for each method

that Qv^ judged not likely to be present in the usual water-analysis laboratory. Some of these items, such as the 3 -y coincidence-counting system of

McCurdy and Mellor (1979), are a significant expense.

-6-
Conclusions

Most of the 2^°Ra assay methods in Table 1 are eliminated from consideration

as an EPA reference method by applying the criteria discussed earlier:

adequate sensitivity, yield determination without radioactive tracers, and a

waiting time for ingrowth or decay of radionuclides in the sample of no more

than 30 days. The methods meeting these criteria, but with the reservation

already noted about each, are Kahlos and Asikainen (1973), Krieger (1976)

and McCurdy and Mellor (1979). The first of these three would be eliminated

if the requirement of a waiting period for ingrowth or decay of no more than

two days were imposed. It is possible that Iyer et al . (1966) and Barratta

and Feldman (1961) are sufficiently sensitive, but multi laboratory studies

would be necessary to demonstrate this.

It is suggested that the EPA keep Krieger (1976) as a reference method but

improve its decontamination factor for ^'-'y and correct its chemical yield

calculation. It is also suggested that McCurdy and Mellor (1979) be added

as a second reference method. The two procedures complement each other.

The first uses radiation-detection systems which most laboratories that

assay for radionuclides in water are likely to have, but it requires a

considerable amount of labor to process samples. The second requires most

laboratories to purchase a new radiation-detection system, but the

labor to process samples is definitely less.

-7-
Literature

Baratta, E.J., and M.H. Feldman (1961), Determination of Actinium in Uranium

Mill Effluents , U.S.A.E.C. Topical Report WIN-123.

Rroecker, W.S., A. Kaufman, and R.M. Trier (1973), "The residence time of

thorium in surface sea water and its Implications regarding the rate of

reactive pollutants", Earth Planet. Sci. Lett., 20^, 35.

Cochran, J.K. (1979), The Geochemistry of ^ ^ ^Ra and^^^Ra in Marine Deposits , Ph. D. thesis, Yale Univ., App. A.

EPA (1976), National Interim Primary Drinking Water Regulations , EPA-570/9-

76-003, U.S.E.P.A., Washington.

FDA (1979), "Quality standards for foods with no identity standards - bottled

water", Fed. Reg., 44 (45), 12169.

Goldin, A.S. (1961), "Determination of dissolved radium". Anal. Chem. , 3_3 , 406.

Hainberger, P.L., I.R. de Oliveira Paiva, H.A. Salles Andrade, G. Zundel

,

and T.L. Cullen (1974), "Radioactivity in Brazillian mineral waters", Radiat.

Data Rep., j_5 (8), 483.

Humphrey, H.W., E.L. Adkins, and G.G. Templin (1975), The Radiometric

Determination of ^ ^ ^Ra and^^^Ra in Waste Effluent Solutions , U.S.A.E.C.

Report NLCO-1084.

Iyer, R.H., H.C. Jain, M.V. Ramaniah, and C.L. Rao (1966), "Estimation of

radlum-228 in monazite and thorium samples", Radlochim. Acta, 5^, 56.

Johns, F.B., P.B. Hahn, D.J. Thome, and E.W. Bretthauer (1979), Radiochemical

Analytical Procedures for Analysis of Environmental Samples , U.S.E.P.A. Report

EMSL-LV-0539-17, Las Vegas.

Johnson, J.O. (1971), Determination of Radlum-228 in Natural Waters , U.S.G.S.

Water-Supply Paper 1696-G, Washington.

Kahlos, H., and M. Asikainen (1973), Natural Radioactivity of Ground Water in

the Helsinki Area , Institute of Radiation Physics Report SFL-A-19, Helsinki.

Kaufman, A., R.M. Trier, W.S. Broecker, and H.W. Feely (1973), "Distribution

of 228Ra -jn ^^^ ^opij ocean", J. Geophys. Res., 78 (36), 8827.

Knauss, K.G., T.-L. Ku, and W.S. Moore (1978), "Radium and thorium isotopes

in the surface waters of the east Pacific and coastal southern California",

Earth Planet. Sci. Lett., 39, 235.

-8-
Koide, M. , and K.W. Bruland (1975), "The electrodeposition and determination of radium by isotopic dilution in sea water and in sediments simultaneously with other natural radionuclides", Anal. Chim. Acta, 7^, 1.

Krieger, H.L. (1976), Interim Radiochemical Methodology for Drinking Water , U.S.E.P.A. Report EPA-600/4-75-008 (Revised), Cincinnati. (Available from

N.T.I.S., Springfield, Va.)

Krishnaswami , S., D. Lai, B.L.K. Somayajulu, F.S. Dixon, S.A. Stonecipher,

and H. Craig (1972), "Silicon, radium, thorium, and lead in seawater: insitu extraction by synthetic fibre", Earth Planet. Sci. Lett., J_6, 84.

Kuchta, D.R.. J. Rundo. and R.B. Holtzman (1976), "Low-level determination

of skeletal ^^Brq and ^^Bj^, -jp ^he presence of gross amounts of ^^^Ra" in

Biological and Environmental Effects of Low-Level Radiation , proc. Symp.

Nov. 3-7, 1975, Chicago; vol. II, p. 183, I.A.E.A., Vienna.

Lund, E. (1976), "Report of a working group on radiological examination of

water". Water Res., JO, 179.

MacKenzie, A.B., M.S. Baxter, I.G. McKinley D.S. Swan and W. Jack (1979),

"The determination of 124^5^ 137^5^ 210pb^ 226pa ^p^ 2Z8pa concentrations

in nearshore marine sediments and seawater", J. Radioanal. Chem. , 48, 29.

McCurdy, D.E., and R.A. Mellor (1979), "An alternative technique for the

determination of '^^^Ra and 228^^ -jp drinking water", presented at 24th ann. meeting of Health Physics Soc, July 8-13, 1979, Philadelphia.

Michel, J., and W.S. Moore (1980), "'^^^Ra and 226^^ content of groundwater

in fall line aquifers". Health Physics, 38^, 663.

Moore, W.S. (1969a), "Measurement of 228pa gp^ 228jh in sea water", J.

Geophys. Res. , U, 694.

Moore, W.S. (1969b), "Oceanic concentrations of ^^^radlum" , Earth Planet.

Sci. Lett. , 6, 437.

Moore, W.S. (1976), "Sampling 228^3 -jp the deep ocean", Deep-Sea Res., 23, 647.

Moore, W.S., and D.F. Reid (1973), "Extraction of radium from natural waters

using manganese-impregnated acrylic fibers", J. Geophys. Res., 28 (36), 8880.

Percival, D.R., and D.B. Martin (1974), "Sequential determination of radium226, radium-228, actinium-227 , and thorium isotopes in environmental and

process waste samples". Anal. Chem., 46, 1742.

Petrow, H.G., and R.J. Allen (1961), "Estimation of the isotopic composition

of separated radium samples". Anal. Chem., 33^, 1303.

-9-
Petrow, H.G., A. Cover, W. Scheissle, and E. Parsons (1964), "Radiochemical

determination of radium-228 and thorium-228 in biological and mineral

samples". Anal. Chem. , 36^, 1600.

Sakanoue, M., T. Nomura, T. Imai, and H. Uzuyama (1973), "Radiochemical

studies on 2^°Ra in sea water and ^Slp^ -jp ggg sediments", in Proceedings

of Symposium on Hydrogeochemistry and Biogeochemistry , Sept. 7-9, 1970,

Tokyo, vol. 1, p. 293.

Sekine, T., Y. Koike, and M. Sakairi (1966), "Studies of actinium (III) in

various solutions, (I) Separation and purification of ^^^Ac in ^28^3

solutions by solvent extraction method", J. Nucl. Sci. Tech., 4-, 308.

Smith, K.A., and E.R. Mercer (1970), "The determination of radium-226 and

radium-228 in soils and plants, using radium-225 as a yield tracer",

J. Radioanal. Chem. , 5^, 303.

Tomza, I. (1977), "Determination of low radium concentrations in mineralized

waters", in Proceedings of the International Conference on Low-Radioactivity

Measurements and Applications , Oct. 6-10, 1975, The High Tatras, Czechoslovakia, p. 387 (in Russian).

Trier, R.M., W.S. Broecker, and H.W. Feely (1972), "Radium-228 profile at the

second Geosecs intercalibration station, 1970, in the north Atlantic", Earth

Planet. Sci. Lett., }^, 141.

Whittaker, E.L. (1980), Environmental Monitoring Systems Laboratory,

U.S. Environmental Protection Agency, Las Vegas; personal communication.

The following papers were obtained too late to include in Table 1. They do

not alter the conclusions of this report because none is suitable as a refer- ence method for radium-228 assays. The radiochemical section of the Herment

paper deals with the production of radium-228. Neither of the other two

papers has a way to determine the chemical yield of an assay.

Herment, M. (1971), Chemical Separation and High Resolution Nuclear Spectroscopy in the^^^Ra ^^"Ac ^^°Th Radioactive Chain , Univ. Grenoble Report

FRNC-TH-184 (in French).

Kharbanda, J.L., M.V. Rajan, R.V. Amalraj, K.T. Thomas (1966), "Separation and

estimation of radium-228 in thorium plant effluent", in Proc. Nucl. Radiat.

Chem. Symp. , Jan. 20-22, 1966, Waltair, p. 46.

Sebessy, L., E. Upor, and I. Vados (1967), "Determination of the radium-226/

radium-228 ratio in natural waters", in Proc. Conf. Appl . Phys.-Chem.

Methods Chem. Anal. , 1966, Budapest, Vol. 2, p. 245.

-10-
Table 1. Comparison of Major Features of Methods for the Assay of

Radium- 2 28 in Water

-11-
Intended Use

Baratta and Feldman

(1961)

Humphrey et

al. (1975r

Iyer et al

(1966T

Johns et al . (1979)

Kahlos and Asikainen

(1973)

Kaufman et a_[ (1973), Broecker et

al- (1973F

Koide and Rruland

(1975)

Krieger

(1975), based

on Johnson

(1971)

Kuchta et^ al . (1976)

Assay of Ac in U mill effluents

and natural wa- ters

"6Ra and "^Ri

in effluent so- lutions with high

ion concentration

Estimation of

Ra in monazite and Th sam- ples

in water, soil

air, and biological samples

Assay of natural radioactivity in ground water

in sea water

226„ 228„

Ra and other natural emitters in sea water and marine

:;r^1ments

in drinking water

if skeleRa and

'Th in pres- ence of gross amounts of ^^^Ra

Assaji

Sample Size

1 liter

250 ml

2 to 5 g

1500 g water,

1 g soil ,-,up to 500 cm of air filter,

biological not specified

1 liter

600 to 800 1

20 1 water, 1 to 5 g sedi- ment

At least 1 liter

Not specified

Preliminaries

Ac pptd. with La (12 mg) by HF

Digest with

HpSO. in Pt dish

and fuse with

NapCO, and K-,CO,, Dissolve in RNO,

Water, none; di- gest soil in Paar bomb, then

fuse; acid dis- solution of air filters

Citric acid and NH.OH added to filtered sample,

then Ba and Pb carriers

Acidify with HCl

add Fe and^Ba

carriers, Th;

ppt. Fe(OH), and Ba(Ra)SO. with

Add Pb carrier,

Ra tracer. Sediment: ignite

and leach with

HCl

Add citric acid,

Pb, Ba, and V carriers; heat

Dry-ash bone

sample, dissolve

ash in HNO,

Ra Separation

On Ba(NO,)p in 70% HNO,: Sul- fate ion inter- feres

On 100 mg of Ba pptd. as BaCOj.

Ba weighed be- fore and after

Ra separation

Water, air filters: coppt. on PbSO^; soil : coppt. on BaSO.

Mixed sulfates

Hydroxides dis- solved in HCl; sulfates transposed to carbonates, dissolved

in HCl

Water: coppt. on AlPO., dissolve

in 4 M HNOj. Sediment: coppt.

on Pb(NO,), with

751 HNO,

Add NH.OH, ppt. mixed sulfates

with HjSO^, then

Purification Final Form

R A D I U M - 2 2 6

Yielded By Counted By

By AG50W-X8 ion exchange column operated at 60°. Fluted with 3 H HNO3

Water and Microsorban filters:

none; soil and glass-fiber filters: reppt. on BaSO^

Dissolve ppt. in alkaline EDTA

solution, reppt. sulfates at pH 4.5 with acetic

acid

None

Separate Ra and

Pb on anion ex- change column,

al kal ine earths

on cation ex- change column

Multiple copptn.

on Ba(NO,), and

on BaSO^

Solution evap.

on stainless

steel planchet, planchet flamed

Water and Microsorban filters:

DPTA complex in acetic acid;

others: chloride

solution

Ba(Ra)SO. on planchet

Rn de-emanated

by He gas. Rn frozen out of He

in liquid air- cooled trap

Electroplated on

Pt planchet after at least two weeks wait for unsupported

Ra tci decay

In aklaline EDTA

solution, or in BaSO^ ppt. on stainless steel planchet

Nothing

Nothing

Weighing of Ba(Ra)SO. ppt.

Nothing. Moore

(lS59b) found

initial sulfate

pptn. to be 605; to 90% efficient

jpyRa tracer.

Ac "cow" is required

BaSO. gravimetricaily

Frisch-grid ioni- zation chamber of 4.78 MeV o<. with

PHA

Rn de-emanated into scintillation chamber after 30 days

ingrowth. Counting begun 4.5 h af- ter transfer

ZnS{Ag)-activated ot-partlcle scin- tillation counter

°^ -scintillation detector

"< -spectrometry with semiconductor detector

Rn de-emanation

into scintillator

cell

•12-
I Special Items Purification

R A D I U M - 2 2

Final For

Heated ion ex- change columns

(60" C)

Paar bomb; Pt dish for glassfiber filter and

soil samples

None. Method

based on that of Goldin (1961)

Liquid air- cooled trap for

Rn

Ac "cow". Ul- trasonic agitator

None

Liquid-liquid extractions using TTA in ben- zene; ion ex- change columns

2nd ion exchange

column at 60 C. Ac eluted with

6 M HNO,

Ac copptd. on Fe(OH),, impurities scavenged

on Pb and Bi sul fides

Reppt. Ba(Ra)SO. dissolve, ex- tract Ac into DEHPA, back ex- tract into 1 M HNO3

Dissolve ppt.

,

add Ce carrier,

transfer to depo

sition cell , add

Te; Pb, Bi , and

Po plate out.

Th copptd,, an Fe(0H)3; ^-^^Th spike added, so- lution stored-, Th copptd. on Fe(OH),

none additional

plus copptn. of ingrown Ac on Y(OH),

None except by

Rn de-emanation

using a flow- through collection chamber

La(Ac) oxalate.

Iyer et aX. (1966Tthink Y is better than

La as carrier

Solution evap.

on stainless

steel planchet

Fe(Ac)(OH), dissolved in HNO3. Known fraction

evap. on planchet

Evap. acid solution to dryness

on 5-cm diameter

planchet

Ppt. Ce with

NaOH, dissolve

ppt. in HNO3, add Ba holdback

carrier, reppt.

Ac on Ce(0H)3

Th purified on cation and anion exchange col- umns, extracted

into TTA in ben- zene, evap.

On same planchet

as Ra

Yielded By

Not mentioned,

but could be gravimetrically

Nothing

Weighings of ppt. containing Ra and

Ac, or spectro photometric as say of Fe

Nothing

Nothing, but

final ppt. could

be Ce oxalate, which is weighable for yield

Ra assays of

sample initially

and during ^^"Th ingrowth plus - SDRctrometry of ^^"Th tracer

J^,counting of ^"Ra

In Y oxalate ppt., Weighing of Y oxalate

Solution i|2rt6- emanated, Rn and progeny col- lected on nega- tively charged electrode

Nothing

Waiting Period Counted By

1

Special Items Comments

None stated, but sample should be two days old be- fore starting assay

ingrowth

ingrowth

About 30 d for

Rn ingrowth;

at least 30 h for "Ac in- growth

out 30 d for

Rn ingrowth

4 to,ll months

for "^"Th in- growth

east 2 weeks

^'^'Pa and

At 1 for progeny to decay

At least 36 h fag ingrowth of

2 counts about 1 year apart for samples without equilibcium beRa and °Th

G-M tube or pro- portional counter, with, absorb

er when Ac is present

Gas-flow proportional counter

with 13 mg/cm

absorber

End-window, gas- flow proportional counter

Low-background

proportional

counter. Time

T, is ambiguously specified

Low-background P counter, type unspecified

"i spectrometry; counting system

not specified

Ac in proportional counter

with Al absorber

Other emitters

nu;.t be flinoJ

off planchet

^^^Ac in gasflow proportional counter

Electrode placed

in holder with ZnS-coated Mylar

disc on,Bhototube. Pb and progeny counted

Sage as for

Pt crucible; spectrophotometer (Fe line at

304 nm used)

None besides, those for "^^"Pa

Constant temper- ature bath, for

the spontaneous electrodeposition step

None additional

None additional

Flow-through

chamber with collection electrode; holder

for electrode on phototube

Sekine et al. (1967) say TTA equimolar with TBP in CCl. is superior to TTA

only

Ba initially present in samples. Na, K, Ca, Mg, and Al each more than 100 mg/1 in typical sam- ple

Method not tried on very

low activity samples

Method could be changed

to assay °Ra first. No specifics given for as- saying biologicals. Sectian 11 wrongly states no

Ra std. are available

Ra could be counted

by de-emanation of Rn

Method is based in part

on Moore (1969a). Knauss

et al_. (1978) found pre- cision of assavs better

by countiRSg Th than by counting Ac

^^^Ra/^^^Ra activity ra- tio must be at leastoO.l.

As check, ingrown Th can be counted later. Cochran (197'>) cor,>|-letely dissolved sediments.

Chemical yield of Ac is incorrectly calculated

see text

Data are analyzed by computer. Method designed

to ha«s poor sensitivity

for "Ra

-13-
Intended Use

1 Sample Size Preliminaries Ra Separation Purification Final Form •RADIUM-226

Yielded By Counted By

MacKenzie et

al. (1979)~

McCurdy and Mellor (1979)

Michel and Moore (1980)

Percival and Martin (1974)

Petrow et al . (1964)

Sakanoue et

al. (1973F

Smith and Mercer (1970)

Tomza (1977)

and other radio- nuclides in sea water and marine

sediments

in drinking water

and Ra in ground waters

in soils, water,

ores, and mill tailings and effluents

AssaujOf ^^^Ra

and '^°Th in biological and mineral samples

228

Ra in sga-, water and Pa

in sea sedi- ments

AssaVpQf Ra and ^'°Ra in soils and plants

Assay of low Ra concentrations

in mineral ized waters

Water: 10 to

29,1 for ^^"Ra-olOOO 1 for ^^^Ra. Sediment: 5 to 10 g

2 1

^^^Ra: 0.8 1; ^^'^Ra: 10 to 20 1

5 g of solids

0.1 to 1 li- ter of liquid

Up to 50 g of bone ash; up

to 20 g of

food or plant

ash; 5 g of minerals

Up to 10 g of plant ash and

soil

Water: filter, acidify. Sediment: complete dissolution in Teflon with mixture of acids

Add citric acid, adjust pH to 9.5

add Ba carrier

(known amount)

None (waters assayed were

clear)

Liquids: acidify

wait overnight,

coppt. on PbSO.,

do sulfate fu- sion

Minerals: fuse with Na-,CO,, di- gest in NaOH.

All types: dissolve in acid

BaCl, and FeCl, added, then NH, Fe(0H)3 and ^ BaSO, ppt.

Repeated evap. with HCIO. and

HF, dissolve

residue in HCl

Add citric acid

and NH.OH, then

Pb and Ba carri226 228

Ra: none.

Ra: absorb on MnOp, desorb

with HCl , coppt.

on BaSO.

On BaSO. pptd.

PjgRa: none.

Ra: absorb on MnOn-impregnated

acrylic fibers, desorb with HCl , ppt. on BaSO.

Add acetic acid,

coppt. Ra with

BaCl, on BaSO.. Dissolve ppt. in DTPA solution

Liquid-liquid extractions with Aliquat 336 and DEHPA to remove

Th. Coppt. Ra on PbSO.

Fe(OH)-, ppt. diS' solved^ith HCl. Ba(Ra)S04 con- verted to car- bonates by fu- sion, dissolved

in HCl

Coppt. Ra on Ba and Pb sulfates.

Ppt. dissolved

in alkaline EDTA sulfates repptd. with acetic acid

Mixed sulfates

pptd. with H^SO^

Dissolve ppt. i alkaline EDTA solution, reppt

BaSO. with acetic acid

None

Cation exchange

separation of Ra and Ba; Ra coppt.

on Pb(N0,)2, sep- arated by anion exchange at 60

Ppt. dissolved

in alkaline EDTA

then repptd. by acetic acid at

pH 4.5

Rn gas

BaSO^ ppt. mixed

with ZnS powder. ZnS/BaSO. ratio

is approximately

2.4

222

Rn gas

222,Rn gas

Electroplated on stainless steel planchet

Ba(Ra)SO. ppt. dispersed in toluene containing PPG, POPOP,

and colloidal

silica

Nothing, but au- thors say assay

is quantitative

Weighing of

BaSO. ppt.

Nothing, but each sample run

at least twice

Nothing

Ba for dissolution only,

Ra for entire

assay, from

"^^^Th "cow"

Nothing

of -scintillation

in modified Lucas

cell

«<->f coincid^we

counting of Ra

•^-scintillation

chamber

Pulse-ionization

chamber or c<- scintiUation

cell

Rn de-emanation

(no specifics given)

>* -spectrometry witJi Frisch-grid pulse- ionization chamber

Liquid-scintillation, two counts

several weeks apart

ABBREVIATIONS:

~- = oc particle ^ = P particle

coppt. = coprecipitate

DEHPA = bis(2-ethylhexyl )phosphoric acid

DTPA = sodium diethylenetriaminepenta acetate

EDTA = sodium ethylenediaminetetraacetate

evap. = evaporate, evaporated

G-M = Geiger-MUller

PHA = pulse height analyzer

POPOP = 1 ,4-di-(2-(5-phenyloxazoyl))-benzene

PRO = 2,5-diphenyloxazole

ppt. = precipitate (as verb and as noun)

-14-
RADIUM-22

Special Items Purification

25-liter glass

vessel for equil

i brat ion of Rn

in water samples

liquid N, -cooled trap for Rn

4 timing SCA, 2 coincidence analyzers, special detector as- sembly, PHA

Apparently none

Heated ion ex- column;

"cow"; tracer

l^^nge

1331'^

Sr removal step; extractions of

Ac by TTA in ben^ zene; store 5 weeks; more ex- tractions of Ac

None additiflpal

See under Ra

Carbonate fusion dissolve mixed

ppt. in HCl , coppt. Th on ^e.

Final Form

Evap. organic

phases on heated stainless steel planchet

store,

coppt.

add '-^ Th

Th on Fe

Remove Ba as sul fate, extract Ac from supernate

into 15% DEHPA, strip into HNO,

Metathesize ppt.

to carbonates, dissolve, coppt.

Ra on PblNOj),; extract Ac with

DEHPA, Aliquat

Extract Ac into DEHPA, back ex- tract into HNO,,

load on Doxex 50

ion exchange col- umn, elute with

6 M HNO3

Coppt. Ac on Fe, solution stored,

Ac reppt. on Fe, Ac separated on anion exchange

column from Fe

Simultaneous

with ^^^Ra

Purify Th by ion exchange, mount

on planchet for

thin source o< counting

Add Ce, coppt.

Ac on Ce exalate

Evap. final acid solution on 5- cm diameter

stainless steel planchet

Evap. on stainless steel plate

Solution evap.

on stainless

steel planchet

me as for

^Ra

Yielded By

says, sample al- S9,assayed for ^^"Ra. Extraction of Ac is not yielded

oC spectKOmetry

of Th, °Ra as- say of concentra

ted samDje. Sep- arate "^'"Ra assay also needed

Nothing

Nothing

Waiting Period Counted By

ingrowth, at least 5 weeks

fflg decay of

Th progeny

228

Ac ingrowth

time not specified, assumed to be 1 to 2 days

a.to 10 d for

Rn ingrowth,

2 tOndomonths

for ""Th in- growth

At least 20 h for "Ac in- growth

At least 36 h for ""Ac in- growth

Tracerlab Omniguard {gas-flow

G-M counter with, anticoincidenc^

fi -?^ coincidences

226„

I Ra assay on initial sample

and on Ba(Ra)Cl2 each of 2 solution just be- ingrowths

fore Ac extraction. Extraction

is not yielded

•^-counting of

Ac, and progeny. '"''Ba not needed if method

used with water

sample

Nothing

Special Items

MnOp-impregnated

acrylic fibers,

Pt crucible

counting of

o< spectrometry

'iio '^ and

Th; counting

system not spec- ified

Gas-flow proportional counter

22;

Unspecified. As- sume 27 d |aK

7 to 10 d far growth of Ac

Equilibcjum be- tween Ra and

Th assumed.

If not so, must reassay several months later

^from decay of

°Ac. Instru- ment unspecified

^jgounting of

Ac in guarded gas-flow proportional counter,

or in Fijitsu

"pico beta" p

spectrometer

Ijgounting^^l

Ac and Ac

in gas-flow pro- portional counteK with 13 mg/

cm absorber

Liquid-scintilla

tion counting of

Ra and progeny. pulses of

Ra discrimina

ted against

^Ige^as for

MnO,-impregnated

acrylic fibers.

See Moore (1976) for preparation

None additional

None additional

Method doB assay of ments(.not discuss

Ra in sediConsiderable instrumen- tation is required, but amount of radiochemistry is reduced

Ra extraction by fibers

based on Krishnaswami et

al . (1972) and on Moore

and Reid (1973)

This method is extention

of similar method by Petrow and Allen (1961

for U mill effluents

which also is unyielded

o<. spectrometry after

several months wait of ^'°Po and ^"^^Ra on the

Ra planchet, without

further chemistry

Use of moderately complex equations of in- growth and decay is re- quired

reppt. = reprecipitate

SCA = single channel analyzer

std. = standard

TBP = tributylphosphate

TTA = 2-theonyl trifluoroacetone

-15-
S.114A (REV. 2-8C) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO. NBS TN 1137

2. Performing Organ. Report No. 3. Publication Date

February 1981

4. TITLE AND SUBTITLE

228, Evaluation of Methods for the Assay of Ra in Water

5. AUTHOR(S)

J.R. Noyce

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No,

8. Type of Report & Period Covered Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State, ZIP)

Quality Assurance Division

Environmental Monitoring Systems Laboratory

U.S. Environmental Protection Agency, P.O. Box 15027

las ypgas, NV 89114

10. SUPPLEMENTARY NOTES

QJ Document describes a computer program; SF-185, PIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or iess factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

The technical literature from 1967 to May 1980 was searched for methods for

assaying radium-228 in water. These methods were evaluated for their suitability as potential EPA reference methods for drinking water assays. We

suggest the present EPA reference method (Krieger, 1976) be retained but improved, and a second method (McCurdy and Mel lor, 1979), which employs B-y

coincidence counting, be added. Included in this report is a table that lists

the principal features of 17 methods for radium-228 assays.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Analysis; assay; evaluation; radioactivity; radiochemistry; radium-228;

reference method; water.

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