PLUTONIUM
196
7. ANALYTICAL METHODS
and purification in conjunction with a quantitative measurement technique (e.g., alpha spectrometry,
liquid scintillation, or mass spectrometry).
7.1 BIOLOGICAL MATERIALS
Methods for the determination of plutonium in biological materials are summarized in Table 7-1. The
procedures that have been developed for the determination of small quantities of plutonium in biological
samples, as well as in environmental samples, include the following steps:
•
Release of plutonium from the sample's matrix into solution and the addition of plutonium
tracers;
•
Concentration by precipitation with a nonisotopic carrier (e.g., lanthanum or neodymium) or by
solvent extraction;
•
Purification by precipitation, liquid extraction, or ion exchange chromatography; and
•
Determination of the plutonium content of the sample by alpha spectroscopy or other techniques.
Two common methods for releasing plutonium from the sample's matrix into solution are acid extraction
and acid dissolution. Samples are wet- or dry-ashed prior to solubilization. Leaching the sample with a
mixture of acids (e.g., nitric acid and hydrochloric acid) has the advantage of easily handling large sample
volumes, but with the potential disadvantage of leaving plutonium compounds in the residue. The acid
dissolution procedure includes the addition of excess hydrofluoric acid (HF) to the above mixture of acids
and results in dissolution of much, if not all, of the sample matrix. Refractory plutonium compounds
(e.g., PuO
2
) are more likely to be dissolved upon addition of HF. However, dissolution of interfering
elements, such as iron, phosphorous, and other rare earths (e.g., alpha-particle emitters) is also increased
in acid dissolution.
A third example of a dissolution method is fusion, which is used primarily for decomposition of
geological and solid environmental media and is suitable for large samples (several grams) (Wolf 2006).
Fusion decomposition is performed by heating a sample with a flux reagent at atmospheric pressure in a
graphite, zirconium, or platinum crucible. Common fluxes include hydroxides, peroxides, carbonates,
bisulfates, hydrosulfates, pyrosulfates, tetraborates, and metaborates. Fusion with sodium hydroxide and
sodium peroxide (NaOH-Na
2
O
2
) is an effective method for decomposition of silica-containing matrices.
A disadvantage of fusion decomposition is that use of a large amount of flux material results in a solution
PLUTONIUM
197
7. ANALYTICAL METHODS
Table 7-1. Analytical Methods for Determining Plutonium in Biological Materials
Sample matrix Preparation method
Analytical
method
Sample
detection limit
Percent
recovery Reference
Tissue
Wet ashed with HNO
3
/H
2
O
2
,
separation by anion
exchange,
ICP-MS
1 fg/mL
No data Yamamoto
et al. 2008a
Urine
Samples were spiked with a
known amount of plutonium
and digested with nitric
acid/hydrogen peroxide
Non-digested (raw) samples
were also analyzed
ICP-MS
0.18 pg/L
(digested
samples after
preconcentration)
1.9 pg/L (raw
samples)
70–100%
(raw
samples)
Epov et al.
2005
Tissue
Wet ashed with
HNO
3
/H
2
SO
4
; collected on
Fe(OH)
2
; separation by ion
exchange and
electrodeposition or
microprecipitation
α spectro
metry
0.0007 Bq
(400 minutes)
No data DOE 1997
Pu-04-RC
Tissue
Wet ashed with HNO
3
/HF;
separation by solvent
extraction; electrodeposition
onto platinum disc
solid state α
spectrometry
0.65 Bq
(400 minutes)
No data DOE 1997
Pu-05-RC
Urine
Wet ashing with
H
2
O
2
/HNO
3
/HCl/HF/H
2
SO
4
;
separation by anion
exchange chromatography;
electrodeposition onto
platinum disc
solid state α
spectrometry
0.60 Bq
(400 minutes)
No data DOE 1997
Pu-06-RC
Urine
Wet ashed with
HNO
3
/H
2
O
2
/HCl; purified by
ion exchange
chromatography
α spectro
metry
No data
No data DOE 1997
Pu-07-RC;
Pu-11-RC
Tissue
Ashed at 400 ºC; dissolved
in HNO
3
/HCl; filtered;
decomposed with HF;
purified by ion exchange
chromatography
α spectro
metry
No data
No data DOE 1997
Pu-08-RC;
Pu-11-RC
Tissue
Digested with HNO
3
/H
2
SO
4
;
coprecipitation of plutonium
with Fe(OH)
3
; purified by ion
exchange chromatography
α spectro
metry
No data
No data DOE 1997
Pu-09-RC;
Pu-11-RC
Tissue
Ashing; electrodeposition
α spectro
metry
No data
No data USTUR
Method 600
Biological soft
tissues
Wet ash; filter; extract;
electrodeposition on
platinum disk
α spectro
metry
No data
No data Singh and
Wrenn 1988
Urine
Evaporate; wet ash; filter;
extract; electrodeposit on
platinum disk
α spectro
metry
No data
No data Singh and
Wrenn 1988
Dostları ilə paylaş: |