International Journal of Analytical Mass Spectrometry and Chromatography, 2013, 1, 72-80
http://dx.doi.org/10.4236/ijamsc.2013.11009 Published Online September 2013 (http://www.scirp.org/journal/ijamsc)
Determination of Lanthanides, Thorium, Uranium and
Plutonium in Irradiated (Th, Pu)O2 by Liquid
Chromatography Using α-Hydroxyiso Butyric
Acid (α-HIBA)
Pranaw Kumar, P. G. Jaison, Vijay M. Telmore, Sumana Paul, Suresh K. Aggarwal*
Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai, India
Email: *skaggr2002@rediffmail.com
Received July 27, 2013; revised August 28, 2013; accepted September 27, 2013
Academic Editor: Prof. N. Sivaraman, HBNI,
India and Head, SCSS, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, INDIA
Copyright © 2013 Pranaw Kumar et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
An HPLC method is presented for the separation and determination of lanthanides (Lns), thorium (Th), uranium (U) and
plutonium (Pu) from irradiated (Th, Pu)O2. Individual separation of Lns, Th, U and Pu is a challenging task because of
1) lanthanides having similar physical and chemical properties, 2) presence of complex matrix like irradiated fuel and 3)
the co-existence of multiple oxidation states of Pu. Different procedures were developed for separation of individual
lanthanides and actinides. The individual lanthanides were separated on a dynamically modified reversed phase (RP)
column using n-octane sulfonic acid as an ion interaction reagent and employing dual gradient (pH and concentration)
of α-hydroxyisobutyric acid (HIBA). In order to improve the precision on the determination of Lns, terbium (Tb) was
used as an internal standard. The method was validated employing simulated high level liquid waste. Concentrations of
lanthanides viz. lanthanum (La) and neodymium (Nd) in the dissolver solution were determined based on their peak
areas. Th, U and Pu were separated on a RP column using mobile phase containing HIBA and methanol. Since Pu is
prone to exist in multiple oxidation states, all the oxidation states were converted into Pu (IV) using H2O2 in 3 M HNO3.
Under the optimized conditions, Pu(IV) eluted first followed by Th and U. The concentrations of Th, U and Pu were
determined by standard addition method and were found to be 1.10 ± 0.02 mg/g, 5.3 ± 0.3 µg/g and 27 ± 1 µg/g, respec-
tively, in the dissolver solution of irradiated fuel. These values were in good agreement with the concentration of Th
determined by biamperometry and those of U and Pu by isotope dilution thermal ionization mass spectrometry.
Keywords: HPLC; Lanthanides; Th; U; Pu;
-HIBA; Irradiated (Th, Pu)O2
1. Introduction
The Indian nuclear program envisages the effective utili-
zation of thorium (Th) as a fertile material for the sus-
tained production of electricity in the country [1]. Unlike
the natural uranium (U) based fuel which contains 235U
as the fissile material, thoria based fuel initially requires
the addition of fissile materials like 233U, 235U and 239Pu
from outside. Mixture of (Th, 233U) O2 and (Th, 239Pu) O2
was proposed as fuel for advanced heavy water reactor
(AHWR) to make system self-sustaining in 233U [2,3]. In
order to assess the performance of (Th, Pu) O2 MOX fuel,
prior to its introduction in commercial reactors, (Th, 4%
Pu)O2 fuel clusters were irradiated in the Pressurized
Water Loop (PWL) of CIRUS reactor, BARC. The im-
plementation of mixed oxide based fuel cycle requires
development of methodologies for evaluating the per-
formance of the fuel in the reactor. Burn-up is an impor-
tant parameter for nuclear fuel development, fuel man-
agement and fuel performance analysis [4,5]. Burn-up is
defined as the atom percent fission of heavy element
(mass 225) during its life time in the reactor. Radio-
chemical and chemical analysis methods are generally
used for burn-up determination of irradiated nuclear fuels
[6]. The destructive method involved dissolution of fuels
followed by individual separation and determination of
*
Corresponding author.
C
opyright © 2013 SciRes. IJAMSC
P. KUMAR ET AL. 73
fission products and heavy elements. Isotope dilution-thermal
ionization mass spectrometry (ID-TIMS) is an estab-
lished method for the determination of burn-up [5,7,8].
Development of new methodologies for the separation
and determination of Lns, Th, U and Pu is essential for
burn-up determination of thorium based nuclear fuel [9].
Different methods based on solvent extraction, ion ex-
change, precipitation, liquid chromatography, etc. have
been reported for the separation of Lns, Th, U and Pu in
various matrices [10,11]. Among these methods, high
performance liquid chromatography (HPLC) is a fast and
highly efficient technique and has been applied for the
separation of lanthanides and actinides in nuclear fuel
samples and geological samples [12-16]. Due to the fast
separation and less amount of the sample handling in
HPLC, it minimizes the exposure to highly radioactive
samples and is, therefore, attractive for the separation of
fission products. Cassidy et al. studied the separation of
lanthanides fission products using a dynamic ion ex-
change column from different fuel samples like UO2 and
(Th, U)O2 fuels [17,18]. However, in presence of bulk of
actinides, the individual separation of lanthanides was
not reported. Lanthanides were separated in a group by
conventional ion exchange method and subsequently
injected into HPLC after removal of Th and U. This off-
line separation requires multiple monitoring elements
and there are chances of loss of analytes. The reported
method gave good reproducibility among different runs
for the same aliquot but results were inconsistent for dif-
ferent aliquots of same fuel. Sivaraman et al. carried out
extensive studies on the separation of lanthanide fission
products for fast breeder test reactor fuels [19-21]. They
determined the stability constant of actinide-HIBA com-
plexes under different chromatographic conditions. How-
ever, (Th, Pu)O2 is a unique fuel tested for AHWR re-
actor and liquid chromatographic method for separation
of Lns from this matrix is not reported in literature.
Various RP based methods have been reported for the
separation of Th, U and Pu using hydroxyl carboxylic
acid like HIBA and mandelic acid [22-24]. In most of the
reported method, the lanthanides, U and Th are present in
comparable amounts. Studies were carried out previously
in our laboratory using ion interaction reagent (IIR) on
the reversed phase (RP) column for the separation of
lanthanides from Th and U [25]. Under the optimized
chromatographic conditions using dual gradient of pH
and concentration of mobile phase, lanthanides were se-
parated out from bulk of Th and U from simulated ir-
radiated thoria sample. However, the separation and de-
termination of Lns, Th, U and Pu from irradiated (Th, Pu)O2
fuel employing HPLC have not been reported so far.
Present paper deals with the individual separation of
Lns, Th, U and Pu in an irradiated (Th, Pu)O2 fuel. Han-
dling of (Th, Pu)O2 fuel samples is more challenging
because of the radiation dose associated with the dissol-
ver solution, presence of large amount of Th which is
vulnerable to hydrolysis and multiple oxidation states of
Pu under the chromatographic conditions [26]. Since the
chromatographic behavior of lanthanides is different than
tetravalent and hexavalent actinides, two different sepa-
ration procedures are developed. The challenges of the
present studies are: 1) individual separation of lanthanide
fission products in presence bulk of Th and interference
of trivalent actinides in Lns separation, 2) difficulties in
the quantification of Pu because of its multiple oxidation
states, and 3) individual separation of Th(IV), Pu(IV) and
U(VI).
2. Experimental
2.1. Instrumentation
The HPLC system consisted of an L-2130 (Elite La-
Chrom, Hitachi) low-pressure quaternary gradient pump
and an L-2450 (Elite LaChrom) diode array detector. C18
monolith RP column (100 mm × 4.6 mm, Chromolith,
Merck) and C18 particulate RP column (150 mm × 4.6
mm, 5 µm, Supelcosil) were used as the stationary pha-
ses. Solutions were injected into the column using a
Rheodyne injector (Model 9725i) with a 100 µL loop.
The eluted species were monitored after post-column reac-
tion with a metallochromic reagent, which was added us-
ing a reciprocating pump (Eldex Laboratories Inc.) into a
low dead volume-mixing tee (Valco). The signal from the
detector was processed by EZChrom software package.
2.2. Reagents
All solutions were prepared using deionised water from
Milli-Q system (Millipore) and were filtered through a
0.45 µm membrane filter (Millipore) prior to using. α-
HIBA (Lancaster) was used as an eluent. Sodium n-oc-
tane sulphonate monohydrate (Fluka) and tetrabutylam-
monium iodide (Sigma-Aldrich) were used as the ion
interaction reagents (IIR). ICP-standards of the lantha-
nides, U and Th (Inorganic Venture) were used after ap-
propriate dilutions with Milli-Q water and mobile phase.
HNO3 and NH4OH (Merck) were used for adjusting the
pH of the mobile phase. H2O2 (Merck) in combination
with HNO3 was used as a redox reagent to bring Pu into
the IV oxidation state. For ion exchange separation,
Dowex 1 × 8, 200 - 400 mesh size (Sigma-Aldrich) and
Bio-Rad AG 1 × 2, 200 - 400 mesh size (Bio-Rad) were
used as stationary phases. Arsenazo (III) (Fluka) was
used as the post-column metallochromic reagent (PCR).
The arsenazo complexes of Lns, Th, U and Pu were
monitored at 653 nm. Irradiated (Th, Pu)O2 sample re-
ceived from Post-Irradiated Examination Division (PIED),
BARC was used for the method development. NIST-
Copyright © 2013 SciRes. IJAMSC
P. KUMAR ET AL.
74
SRM-950a U3O8, K4Pu(SO 4)4 and enriched isotope of
142Nd were used as spikes for ID-TIMS analysis of U, Pu
and Nd, respectively.
2.3. Procedure
Appropriate quantities of α-HIBA and sodium n-octane
sulfonate were dissolved in water and made to solutions
with concentrations 0.5 M and 0.1 M, respectively. α-
HIBA was adjusted to the desired pH using high-purity
NH4OH and HNO3. Mobile phase flow-rate of 1.0 mL
min1 was used. The PCR solution [1.5 × 104 M Ar-
senazo (III) and 0.01 M urea in 0.1 M HNO3] was deliv-
ered at a flow rate of 0.3 mLmin1.The lanthanides, Th,
U and Pu solution of appropriate concentrations were
prepared after dilution with mobile phase. Concentration
of Pu was determined by biamperometry titration [27].
Dissolution of irradiated fuel sample was carried out in a
facility housed in a shielded glove box. Aliquots from the
irradiated fuel dissolver solution were transferred to a
shielded fume-hood for further experiments.
For the determination of Lns, about 0.5 g of dissolved
sample solution was taken and 2.5 ppm of Tb was added
as an internal standard. This solution was directly in-
jected into HPLC through 100 µL injection port. The
mobile phase containing α-HIBA of pH 6.5 was changed
from 0.05 M to 0.15 M in 30 min; whereas α-HIBA of
pH 3.5 was changed from 0.15 M to 0.3 M in a time in-
terval of 30 to 40 min. A C18 RP column (250 mm × 4.6
mm) was used for the individual separation of Lns. For
validation of method using ID-TIMS, all the aliquots
were subjected to necessary chemical treatments to en-
sure depolymerisation and proper isotopic homogeniza-
tion. The spiked and unspiked aliquots were used for
separation by anion exchange using Dowex 1 × 8, 200 -
400 mesh resin in 9 M HCl medium [8]. The effluent
containing Th and fission product fraction was collected.
Pu and U fractions were sequentially eluted from the
column using 0.1 M hydroxylamine hydrochloride in 5M
HCl and 0.5 M HNO3, respectively. The fraction con-
taining Th and fission products was subjected to a second
stage anion-exchange separation using Dowex 1 × 8200 -
400 mesh resin in 7 M HNO3 medium. The non-retained
fission product fraction was collected and subjected to a
third stage separation using Bio-Rad AG 1 × 2200 - 400
in a mixture containing HNO3 and MeOH to separate Nd
fraction [8].
3. Results and Discussion
3.1. Separation and Determination of Lns from
Irradiated (Th, Pu)O2
3.1.1. Chromatographic Behavior of Lanthanides, Th,
U and Pu
In solution, under the chromatographic conditions, lan-
thanides exist in III oxidation state whereas Th and U
exist in IV and VI states, respectively. The situation in
the cases of Pu is different. In view of the closeness of
redox potential values, Pu can exist in different oxidation
state viz. III, IV and VI simultaneously. Retention behav-
iors of Lns and Pu(III) is different from Th(IV), U (VI),
Pu(VI) and Pu(IV) when α-HIBA was used as an eluent
on RP column [21].With α-HIBA, Lns and Pu(III) form
mainly cationic complexes which are different from
those formed by Th, U, Pu(VI) and Pu(IV) [25]. Thus
Lns-HIBA complexes can be separated on dynamically
modified RP column using an IIR which is sorbed unto
the column converting hydrophobic surface into the
charged surface, for ion exchange separation of lantha-
nides [28]. However, Th, U and Pu(IV) get sorbed onto
the RP column by hydrophobic interaction, when α-
HIBA is used as a complexing reagent. In presence of
large amounts of IIR, the actinides were found to elute in
between the lanthanides which makes lanthanides deter-
mination difficult. Hence, at a given concentration of IIR,
the surface of RP column remains partly ionic and hy-
drophobic in nature. The separation of lanthanides from
Th, U and Pu was performed using dual gradient (pH and
Concentration) of α-HIBA. At higher pH, tetravalent and
hexavalent actinides are retained better than lanthanides
on dynamically modified reversed phase column leading
to the elution and separation of lanthanides prior to acti-
nides. Due to the complex nature of irradiated (Th, Pu)
O2 fuel matrix, two different separation procedures were
developed as presented in Scheme 1. In the first stage,
Lns were separated and determined on dynamically
modified column whereas the separation and determina-
tion of Th, U and Pu was achieved using RP column.
3.1.2. Determination of Lanthanides in Irradiated
(Th, Pu) O2 Sample by HPLC
A C18 reversed-phase column, dynamically modified
with n-octane sulphonate, was used as the stationary
phase for separation of lanthanides from irradiated (Th,
Pu)O2 fuel. It was reported that with increase in the con-
centration of IIR, the retention of Lns increases whereas
the retention of Th and U decreases [28]. Th being the
matrix element in the present case, the concentration of
IIR selected was 5 mM to separate Lns without affecting
the Th holding capacity. Effect of pH showed that at
lower pH, higher fraction of HIBA remains in the uni-
nonized form, resulting in faster elution of U and Th
whereas, at pH 5.0, Th and U showed stronger reten-
tion than lanthanides and eluted after Lns. With the in-
crease in concentration of HIBA at pH 4.0, Lns, Th and
U showed decrease in retention. Dual gradient (pH and
concentration) of HIBA was used for the separation of
Lns, Th, U and Pu. Pu was found to elute as multiple
peaks in chromatographic run due to the presence of its
Copyright © 2013 SciRes. IJAMSC
P. KUMAR ET AL.
Copyright © 2013 SciRes. IJAMSC
75
Dissolver solution of Irradiated (Th, Pu)O
2
Evaporate to dryness
Redox treatment with 3M HNO
3
& 30% H
2
O
2
Treatment with concentrated HNO
3
Evaporate to near dryness
Eva
p
orate to near dr
y
ness
Re-dissolve in 1 M HNO
3
and take aliquots
Aliquot for Lns separation
LC separation on
a RP column as per the
conditions given in Figure 1
Aliquot for Th, U and Pu separation
Dissolve in 0.5 M HIBA of pH 6.0
Separate U and Pu on RP
column as per the conditions
given in Table 2
For Th determination, a
portion dilute to 200 times
and separate on RP column
as per the conditions given in
Table 2
Add terbium
(internal
sta ndard )
Scheme 1. Flow chart for liquid chromatographic separa tion of Lns, Th, U and Pu from irradiated (Th, Pu)O2 fuel.
multiple oxidation states. Hence, dissolver solution was
evaporated to near dryness and treated with H2O2 in 3M
HNO3 to convert all the Pu into (IV), and Pu was
re-dissolved in 0.1 M HNO3 to maintain in single oxida-
tion state. Lns were separated by using the gradient con-
dition. Initially, HIBA of pH 6.5 was used for the separa-
tion of lanthanides followed by elution of actinides with
HIBA of pH 3.0. Under these chromatographic condi-
tions, Pu(IV) elutes along with Th and U and hence does
not cause any interference to the lanthanide peaks. Hence-
forth Th, U and Pu are in the oxidation states, Th(IV),
UO2
2+ and Pu(IV), respectively. The response of the Lns
with post-column regent was found to vary with the mo-
bile phase concentration and pH. Therefore, terbium was
used as an internal standard. The advantages of internal
standard approach are: 1) calibration plot for a wide
concentration range is not required. Single injection of
the sample is sufficient, and 2) matrix effects do not in-
fluence the results since the standard is introduced into
the sample. Relative response factors (RRF) for the indi-
vidual Lns pairs were calculated using the simulated
samples. For a pair of Tb and La, the RRF can be calcu-
lated as
TbLaLa Tb
RRF CCAA
where, C and A represent concentration and absorbance
(peak area) of the lanthanides, respectively.
The RRFs of the different pair of La/Tb, Pr/Tb, Nd/Tb
and Sm/Tb were found to be constant and are presented
in Table 1.Validation of lanthanides determination was
carried out by employing a simulated high level liquid
waste solution. Concentrations of lanthanide fission
P. KUMAR ET AL.
76
Table 1. Relative response factors (RRF) for the lanthanides
pairs.
Lanthanide pair RRF
La/Tb 0.94
Ce/Tb 1.03
Pr/Tb 0.77
Nd/Tb 0.92
Sm/Tb 0.89
Figure 1. Direct injection of dissolver solution of irradiated
(Th, Pu)O2 fuel. Conditions: α-HIBA of pH 6.5 changed
from 0.05 M to 0.15 M in 30 min; α-HIBA of pH 3.5
changed 0.15 M to 0.3 M from 30 min to 40 min; Column:
C18 RP (250 mm × 4.6 mm).
products (La, Ce, Pr, Nd and Sm) were determined based
on their peak area employing terbium as an internal
standard. Figure 1 shows the chromatogram of the sepa-
rated lanthanides from the irradiated sample. Concentra-
tions of La, Pr, Nd and Smin the dissolver solution of
irradiated (Th,Pu)O2 sample were determined based on
the internal standard approach and were found to be 0.6 ±
0.05 μg/g; 0.4 ± 0.01 μg/g; 1.8 ± 0.1 µg /g and 0.5 ± 0.02
μg/g, respectively.
3.2. Optimization of Chromatographic
Conditions for the Separation of Th, U
and Pu
U forms [UO2(IBA)]+, [UO2(IBA)2] and [UO2(IBA)3]
whereas Th and Pu form [M(IBA)]3+, [M(IBA)2]2+,
[M(IBA)3]+ and [M(IBA)4] (M = Th or Pu) types of com-
plexes with HIBA [21,29]. Dominance of one species
over the other depends upon the pH and concentration of
HIBA which is responsible for the relative difference in
the retention times of Th, U and Pu. Hence the effects of
chromatographic conditions such as pH of the mobile
phase, concentration of HIBA on the retention of Th, U
and Pu was studied.
3.2.1. p H of Mobil e Phase
Figure 2 shows the effect of pH of the mobile phase on
the retention behavior of Th, U and Pu. At pH 2.5, Pu
2.0 2.5 3.0 3.5 4.0 4.5
5
10
15
20
25
30
35
40
Retention time (min)
pH of mob ile phase
U
Pu
Th
Figure 2. Effect of pH of the mobile phase on the retention
of Th, U and Pu. Chromatographic conditions: 0.1 M of
HIBA and Column: C18 RP (100 mm × 4.6 mm, Chromo-
lith).
showed strong retention compared to Th which in turn
showed stronger retention than U. This is due to the fact
that at lower pH, Pu and Th form predominantly M(IBA)4
type of species whereas U exists as cationic species.
However, at pH 3.5, retention of U drastically in-
creases compared to marginal increase in the retention of
Th and Pu. This is because at higher pH, Th and Pu un-
dergo hydrolysis and must be forming [Th(IBA)4(OH)n]n
and [Pu(IBA)4(OH)n]n (where n = 1 or 2) species, re-
spectively. Being the anionic species, Th and Pu com-
plexes show relatively poor retention on the RP column.
In the case of U, the dominating species at higher pH are
[UO2(IBA)2] and [UO2(IBA)3], which are sufficiently
hydrophobic in nature and exhibit strong retention on RP
column. With further increase in pH 5.0, U was not
eluted till 60.0 mins whereas the retention time of Th and
Pu was 13.3 and 9.9 mins, respectively. Finally, pH 4.3
of the mobile phase was chosen for studying the effect of
concentration of HIBA.
3.2.2. Effect of Concentration of HIBA
Retention behavior of Th, U and Pu was studied as a
function of concentration of α-HIBA at pH 4.3. As it is
seen in Figure 3, the retention of Th, U and Pu were de-
creasing with the increase in concentration of HIBA. The
decrease in the retention times of the actinides with in-
crease in concentration of HIBA is attributed to the
competition between the undissociated HIBA molecules
and actinide-HIBA complex for the C18 stationary phase.
With the increase in concentration of HIBA used as an
eluent, the number of undissociated HIBA molecules in
the mobile phase increases and this results in faster dis-
Copyright © 2013 SciRes. IJAMSC
P. KUMAR ET AL. 77
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
0
10
20
30
U
Pu
Th
Retention time (min)
HIBA concentration (M) in mobile phase
Figure 3. Effect of concentration of α–HIBA in the mobile
phase on the retention of Th, U and Pu. Chromatographic
conditions: pH of mobile phase, 4.3 and other conditions are
same as in Figure 2.
placement of actinide-HIBA complexes from the station-
ary phase. However, retention of U decreased drastically
indicating the hydrophobic nature of U-HIBA complex.
0.1 M of HIBA was chosen for separation studies.
3.3. Mechanism of Retention of Th, U and Pu
To study the mechanism of retention of Th, U and Pu on
the RP column, n-octane sulphonic acid (IIR) was intro-
duced in the mobile phase with the varying concentration.
Figure 4 shows the change in retention of Th, U and Pu
as a function of concentration of n-octanesulphonate
(n-OSA). The sorption of n-octanesulphonate on the sta-
tionary phase results into the formation of cation ex-
change sites. Dominance of cationic species [M(IBA)]3+,
[M(IBA)2]2+, [M(IBA)3]+ of Th and Pu would be indi-
cated by an increase in the retention time with increase in
the concentration of IIR. As seen from the Figure, the
retention times of Th, U and Pu decrease with increase in
the concentration of n-octanesulphonate. This shows that
the retention of Th, U and Pu on RP column is by hy-
drophobic mechanism and there is competition from the
hydrophobic n-octanesulphonate. The studies on the in-
fluence of n-octane sulphonate clearly indicate that the
hydrophobic character of U-HIBA is much higher than
those of Th-HIBA and Pu-HIBA. The sorption of the IIR
molecules onto the stationary phase is also occurring
based on the hydrophobic interaction. U-HIBA complex
shows a pronounced fall in retention time with the in-
creasing concentration of IIR, owing to its highest hy-
drophobic character.
3.4. Effect of Composition of MeOH on the
Retention of Th, U and Pu
0.000 0.005 0.010 0.015 0.020
0
5
10
15
20
25
Retention time (min)
Conc . (M) of n-OSA in mobile phase
U
Pu
Th
Figure 4. Effect of n-octane sulphonate on the retention of
Th, U and Pu. Chromatographic conditions: Concentration
of HIBA, 0.1 M and pH 4.3, Column: C18 RP (100 mm × 4.6
mm, Chromolith).
0510 15 20
0
5
10
15
20
25
Retention ti me ( min s )
Composition of MeOH in mobile phase (%)
U
Pu
Th
Figure 5. Effect of composition of MeOH in mobile phase on
ith change in percentage of MeOH in the mobile phase.
3.5. Separation and Determination of Th, U and
The
the retention of Th, U and Pu. Chromatographic conditions:
same as Figure 4.
w
The retention of U decreases drastically compared to that
of Th and Pu which indicates relatively more hydropho-
bic nature of U-HIBA complex. The presence of MeOH
also resulted in improving the peak shape and shortening
the retention time. Since Th and Pu separation was get-
ting affected at higher percentage of MeOH, it was pro-
posed to use MeOH as a gradient for the separation of Th,
U and Pu from the actual dissolver sample.
Pu from Irradiated (T h, Pu)O 2 by RP-HPLC
above optimized chromatographic conditions were
Figure 5 shows the retention behavior of Th, U and Pu
Copyright © 2013 SciRes. IJAMSC
P. KUMAR ET AL.
78
Table 2. Gradient condition for separation of Th, U and Pu.
Time HIBA (pH = 6.5) HIBA (pH=2.0) % MeOH
(mins) (M) (M) (v/v)
0.00 0.125 0.005 7
10.00 0.125 0.05 7
20.00 0.125 0.05 30
30.00 0.125 0.05 30
sed for the sequential elution of Pu, Th and U. In order
3.6. Validation of HPLC Method
ass spectrometric
u
to improve the resolution between Th and Pu, gradient
condition, as given in Table 2 was employed. To improve
the resolution as well as Th holding capacity, a larger
stationary phase of dimension 250 mm × 4.6 mm was
used. Aliquots of irradiated sample were evaporated to
near dryness and were taken in the mobile phases con-
taining pH 6.5 of 0.13 Mα-HIBA, and were injected
through 100 µL injection port. As shown in Figure 6,
lanthanides and other trivalent species are eluted at the
solvent front. Th, U and Pu are retained on the column
because of the formation of hydrophobic species using
α-HIBA as an eluent. Under the optimized conditions,
the elution pattern was Pu (IV) followed by Th and U.
This is due to the fact that at higher pH for Th and
Pu(IV), M(HIBA)4 type of species are most dominating
whereas for U, [UO2(IBA)3] is the major species. How-
ever, the lower retention time of Pu and Th compared to
U can be explained on the basis of strong hydrolysis na-
ture of Th and Pu (IV) in the chromatographic conditions
resulting in the formation of [M(IBA)4(OH)2]2. The
concentrations of Pu, Th and U were determined by
standard addition method and were found to be 27 ± 1
µg/g, 1.10 ± 0.02 mg/g, and 5.3 ± 0.3 µg/g, respectively,
in the dissolver fuel solution.
Isotope dilution-thermal ionization m
(ID-TIMS) methodology was employed for the concen-
tration determination of U, Pu and Nd in the dissolver
fuel samples. Chemical separation of U, Pu and Nd frac-
tions in the dissolver solution was carried out to elimi-
nate the potential isobaric interferences during the mass
spectrometric analysis as well as to get good ion yield in
TIMS. Nd, U and Pu fractions obtained from unspiked
and spiked aliquots were used to determine isotopic
composition and concentration by ID-TIMS, respectively.
Concentrations of U, Pu and Nd in the sample were
found to be 5.3 ± 0.3 % g/g, 26.8 ± 0.2% g/g and 1.8 ±
0.2% g/g, respectively. Concentration of Th in the dis-
solver solution, determined biampero metrically using
EDTA as a titrant, was found to be 1.03 ± 0.2% mg/g
[30]. The concentrations of Nd, Th, U and Pu obtained
were in good agreement with the concentrations deter-
mined by HPLC.
Figure 6. Direct injection of dissolver solution of irradiated
4. Conclusion
employing α-HIBA was developed for
5. Acknowledgements
. Ramakumar, Director,
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