PLUTONIUM
201
7. ANALYTICAL METHODS
Sensitive methods for analysis of plutonium in urine are particularly important for estimating
occupational plutonium body burdens. Routinely available instrumentation,
such as the alpha
spectrometer, can readily detect these low concentrations. More sensitive methods are commonly
required for urine samples in order to assess chronic exposures to plutonium. These low detection limits
were first achieved in the past by nuclear emulsion track counting. In this method, the electrodeposited
sample is exposed to
nuclear track film, subsequent to the isolation of plutonium. The alpha-particle
emitting isotopes of plutonium will leave tracks on the film, which are counted to quantify the amount of
plutonium. Nuclear emulsion track counting has been used in the past to measure plutonium
concentrations in the urine of workers at a nuclear reactor plant (Nielson and Beasley 1980).
A type of
scintillation counting has been used to measure
239
Pu and americium-241 (
241
Am) in animal tissues
(NCRP 1985).
Epov et al. (2005) reported a method where nondigested urine samples could be analyzed with a detection
limit of 1.9 pg/L. The authors noted that in the case of an emergency, urine analysis without digestion
could provide a rapid determination (about 1 hour) of plutonium levels in urine. However,
sample
digestion would be needed if more precise and sensitive analysis is required. Four hours are required to
analyze urine samples with digestion (Epov et al. 2005).
7.2 ENVIRONMENTAL SAMPLES
Methods for the determination of plutonium in environmental samples are summarized in Table 7-2. The
separation and extraction methods used to prepare biological samples for plutonium analysis are
commonly used for environmental samples. Large volumes of air samples (e.g., 10,000 m
3
) should be
collected in order to obtain detectable amounts of plutonium in particulate in air (EPA 1976a).
Field survey instruments for measuring photons of
241
Am in surface soils and on airborne particulates are
available (e.g., Field Instrument for Detecting Low Energy Radiation or FIDLER) with a minimum
detection limit of approximately twice the magnitude of a background
level of
239
Pu (1x10
3
–
2x10
3
pCi/m
2
; 37–74 Bq/m
2
). The FIDLER uses a sodium iodide or calcium fluoride crystal and photon-
height discrimination in order to detect the 17 keV x-rays emitted from the progeny of plutonium, or the
60 keV gamma photons of
241
Am. These instruments are useful for identifying areas
of contamination,
but cannot be used to accurately predict the concentration of plutonium in surface soils (EPA 1976a).
This instrument has been used in aerial surveys of large area sources, such as the Nevada Test Site.
PLUTONIUM
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7. ANALYTICAL METHODS
Table 7-2. Analytical Methods for Determining Plutonium in Environmental
Samples
Sample
matrix
Preparation method
Analytical
method
Sample
detection
limit Recovery Reference
Air filter,
soil, water,
vegetation
Fusion with KF and
pyrosulfate; dissolution
in HCl; coprecipitation
on BaSO
4
; dissolution of
α spectrometry
No data
85–95%
DOE 1999c
CHEM-TP-A.20
BaSO
4
and
reprecipitation with
DPTA
Water
Separation of
radionuclides by
Eichrom resins
α spectrometry
0.6 mBq
(400 minutes)
93%
DOE 1997
Se-03
Soil
Plutonium isotopes are
leached
from soil using
HNO
3
/HCl
α spectrometry
1 mBq
(400 minutes)
No data
DOE 1997
Pu-02-RC
Air filter
Digestion with HNO
3
followed by treatment
with HF; decompose
filters composed of
organic polymer
overnithe at 450 ºC prior
to digestion
α spectrometry
No data
No data
DOE 1997
Pu-01-RC;
Pu-11-RC;
G-03
Soil,
sediment
Plutonium isotopes are
leached with HNO
3
/HCl;
purification
by ion
exchange
chromatography;
microprecipitation
α spectrometry
1 mBq
(400 minutes)
No data
DOE 1997
Pu-12-RC
Water
Heated in HNO
3
/HCl;
evaporation and
dissolution in HNO
3
;
α spectrometry
No data
No data
DOE 1997
Pu-07-RC;
Pu-11-RC; G-03
purified by ion
exchange;
microprecipitation
Vegetation Ashed at 400 ºC;
dissolved in HNO
3
/HCl;
filtered; decomposed
with HF; purified by ion
exchange
chromatography
α spectrometry
No data
No data
DOE 1997
Pu-08-RC;
Pu-11-RC
Vegetation Digested with
HNO
3
/H
2
SO
4
;
coprecipitation of
plutonium with Fe(OH)
3
;
purified by ion exchange
chromatography
α spectrometry
No data
No data
DOE 1997
Pu-09-RC;
Pu-11-RC
PLUTONIUM
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7. ANALYTICAL METHODS
Table 7-2. Analytical Methods for Determining Plutonium in Environmental
Samples
Sample
Analytical
Sample
matrix
Preparation method method
detection limit Recovery Reference
Food
HNO
3
, closed-vessel
ICP-MS
0.020 pg/g
100±20% Evans et al. 2003
microwave digestion
Air
Dry ash; filter; extract;
α spectrometry
No data
No data
EPA 1984
reduce valence;
(EPA Method
coprecipitate with
00-04)
lanthanum fluoride
Soil, coal, Ashed or evaporated;
α spectrometry
No data
No data
EPA 1984 (EPA
fly ash,
dissolved with HF,
Method Pu-01)
ores,
HClO
4
, and HCl;
vegetation, extraction with
biotia, and triisooctylamine/p
water
xylene; stripped with
HNO
3
; wet ashed; co
precipitated with
lanthanum fluoride;
filtration
Water, soil, Ashing; ion exchange
α spectrometry
0.02 pCi/sample No data
EPA 1979
air,
separation;
vegetation, electrodeposition
and animal
tissue
Water
Filter; extract;
α particle
No data
No data
EPA 1980
coprecipitate with
counter (either
(EPA method
lanthanum fluoride
proportional or
907.0)
scintillation
detectors)
Drinking
Acidify; oxidation with
α particle
No data
93%
EPA 1982 (EPA
water
sodium nitrite;
counter
Method 911)
precipitation; extraction
with tri-isooctylamine;
co-precipitated with
lanthanum fluoride
DPTA = diethylenetriamine-pentaacetic acid; ICP-MS = inductively coupled
plasma-mass spectrometry