As an integral part of chemical quality control of nuclear materials a method for determination of uranium and

zirconium, in a mixture is presented. A simple, cheap, selective and quantitative Flow Injection Analysis (FIA)

system was developed. Zirconium and uranium were determinate in presence of each other and no prior

separation was needed. Arsenazo III was used as a colorimetric reagent and parameters such as acidity and

reagents concentration were studied and optimized. An analytical throughput of 30 sample determination per

hour was obtained

Domingues, Maria de L. F.

Jesus, Camila S.

Rocha, Valeska P. de Araújo

Sousa, Alfaro Serafim F. de

Carpe dIEN

2013 International Nuclear Atlantic Conference - INAC 2013 
Recife, PE, Brazil, November 24-29, 2013 
ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN 
ISBN: 978-85-99141-05-2 
 
DETERMINATION OF URANIUM AND ZIRCONIUM BY 
FLOW INJECTION ANALYSIS 
 
Alvaro S. F. de Sousa1, Maria de L. F. Domingues1, Valeska P. de Araujo Rocha1 and 
Camila S. de Jesus1,2 
 
1
 Instituto de Engenharia Nuclear (IEN / CNEN) – Divisão de Engenharia Nuclear 
Serviço de Química nuclear e Rejeitos – Rua Hélio de Almeida, 75 
Cidade Universitária - Ilha do Fundão –Rio de Janeiro – RJ – Brasil - CEP 21941 906 
alvaro@ien.gov.br 
valeska@ien.gov.br 
luma@ien.gov.br 
 
 
2
 Industrias Nucleares do Brasil  (INB/CNEN) –  Diretoria de Recursos Minerais - Av. João Cabral de Mello 
Neto, n° 400 sala 101 a 304 - Barra da Tijuca - Rio de Janeiro – RJ – CEP 22775-057 
camilasaj@gmail.com 
 
 
 
 
ABSTRACT 
 
As an integral part of chemical quality control of nuclear materials a method for determination of uranium and 
zirconium, in a mixture is presented. A simple, cheap, selective and quantitative Flow Injection Analysis (FIA) 
system was developed. Zirconium and uranium were determinate in presence of each other and no prior 
separation was needed. Arsenazo III was used as a colorimetric reagent and parameters such as acidity and 
reagents concentration were studied and optimized. An analytical throughput of 30 sample determination per 
hour was obtained. 
 
 
1. INTRODUCTION 
 
 
Spectrophotometry is the cheapest and simplest instrumental technique used for the 
determination of uranium and zirconium. However, the application of this technique is almost 
difficult to the simultaneous determination of uranium and zirconium, because the absorption 
spectra of the chromophores created by these elements, generally, overlap in bright region 
and the superimposed curves are not suitable for quantitative evaluation [1]. The use of FIA 
with spectrophotometric detection in order to determine simultaneously elements which 
present superimposed curves has been demonstrated to be a feasible and promising 
alternative for analytical purposes [2]. 
 
Similarly, uranium and thorium present the same difficult and can be easily detected and 
quantified in presence, one each other in a FIA system with spectrophotometric detection [2] 
despite of the interference of the superimposed curves that are produced by the crhomophore 
used. Basically the technique consist in measure the signal produced by Th(IV) and U(VI) 
together, and then again by reduced the U(VI) to U(IV), in presence of Arsenazo III in strong 
INAC 2013, Recife, PE, Brazil. 
 
acid media . The first measurement correspond only to the Th(IV) signal and the second 
measure to the Th(IV) and the U(IV) signal. The difference between the second and the first 
measure gives the signal correspondent to the uranium. This is possible because U(VI) has no 
notable signal in the conditions used, and only U(IV) is detected. 
 
The goal of this work was to develop and optimize an on line system that determine uranium 
and zirconium in presence one each other. Several physic-chemical parameters were 
evaluated and optimum conditions for the determination of uranium and zirconium were 
established. The uranium concentration in the samples was determined by spectrophotometry 
with Arsenazo III using a FIA system. 
 
 
2. EXPERIMENTAL 
 
 
2.1.  Reagents and Solutions 
 
 
All solutions were prepared from analytical-reagent grade by adequate dilution in tri-distilled 
water. Uranium and zirconium stock solutions (500 mg L-1) were prepared by dissolving the 
appropriated amount of UO2(NO3)2.6H2O (Merck) and ZrCl4 (Aldrich) in HCl 3.6 mol L-1. 
The carrier stream was HCl 3.6 mol L-1 and Arsenazo III (Fluka) 1.0·10-4 mol L-1 in HCl 3.6 
mol L-1 was used as the reagent solution. Lead powder (0.1 - 0.3 mm particle size, Merck) 
was used for uranium reduction onto the mini column. Pitchblende (IAEA) sample (0.075 
mm particle size), were dissolved by HCl and HNO3 (Merck) and later analyzed by ICP-MS 
showing the following results in U3O8: P3 = 0.036 ± 0.001 %.  
 
 
2.2.  Instrumentation and Apparatus 
 
 
The absorption spectra (400 nm to 800 nm) were obtained using glass cells with 10 mm 
optical path using a spectrophotometer UV / Visible double beam model GBC UV / VIS 918. 
 
The FIA set-up system for uranium and zirconium determination (Figure 1) consist of: a 
Gilson Miniplus 2 HP-8 (France) peristaltic pump, two Rheodyne 5041 (Cotati, CA, USA) 
six-port valves, one 250 µL loop sampler. Polypropylene connection (inverted Y shape), one 
glass/polypropylene column (2 ID x 300 mm length) filled with lead powder, one stitched 
mixer in PTFE tube (0.8 ID x 300 mm length), a GBC UV/VIS 911A (Australia) UV-vis 
spectrophotometer set at 665 nm with a Hellma (Jamaica, NY, USA) standard glass flow cell 
of 80 µL internal volume and 10 mm optical path and a computer for data collection. 
 
 
INAC 2013, Recife, PE, Brazil. 
 
R1
RG
M
V
R
BP
R2
D
VC
 
 
Figure 1.  FIA set-up system for uranium and zirconium determination: (BP) peristaltic 
pump, (V) six-port injection valve with 250 µL loop sampler , (VC) six-port injection 
valve with a glass/polypropylene reduction column, (M) stitched mixer, (R1) carrier 
solution HCl 3.6 mol L-1, (R2) reagent solution Arsenazo III 1.0·10-4 mol L-1 in HCl 3.6 
mol L-1 media, (R) waste, (D) GBC UV/VIS 911A UV-vis spectrophotometer, (RG) 
computer. 
 
 
2.3.  General Procedure: 
 
 
2.3.1.  Flow injection system for uranium and zirconium determination 
 
 
The FIA system for uranium and zirconium determination, depicted in Figure 1 is started with 
the valve (V) in the load position. The loop is filled with sample or standard solutions, while 
the HCl 3.6 mol L-1 carrier stream (R1), bypass through the reduction column in (VC), and 
then is mixed with the reagent stream Arsenazo III 1.0·10-4 mol L-1 in HCl 3.6 mol L-1 media 
(R2), yielding a final stream that allows the establishment of the signal (for zirconium). In the 
second step the loop is filled again with sample or standard solutions, while the HCl 3.6 mol 
L-1 carrier stream (R1), pass though the reduction column in (VC), and then is mixed with the 
reagent stream Arsenazo III 1.0 · 10-4 mol L-1 (R2), yielding a final stream that allows the 
establishment of the signal (for zirconium plus uranium). 
 
 
2.3.2. Uranium and zirconium signals 
 
 
The following equation was used to calculate the uranium signal in the FIA system. 
 
SU = S(Zr4+U4)-S(Zr4+U6) (1) 
 
Where S(Zr4+U4)-and S(Zr4+U6) are respectively the signals of zirconium and uranium when the 
sample or standard solutions passed through the reduction column and bypassed though the 
reduction column. SU is the uranium signal used in the uranium analytical curve to calculate 
the uranium concentration and the S(Zr4+U6) is also the signal correspondent to zirconium 
INAC 2013, Recife, PE, Brazil. 
 
signal, which is used in the zirconium analytical curve to calculate the zirconium 
concentration. 
 
 
3. RESULTS AND DISCUSSION 
 
 
3.1.  Absorption spectra 
 
 
The profiles obtained for the complexes of Zr(IV)-Arsenazo III; U(VI)-Arsenazo III and 
U(IV)-Arsenazo III between 620 and 680 nm (Figure 2) indicates a difference between 
maximum absorption for both (U (VI ) of 653 nm and the U (IV) at 664 nm) and the 
superimposed curves of the uranium and zirconium Arsenazo III complexes. 
 
400 500 600 700 800
-0,20
-0,15
-0,10
-0,05
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
Zr(IV)
U(VI)
U(IV)
Arsenazo III
A
bs
o
rb
a
n
ce
nm
 
Figure 2.  Absorption spectra (400 nm to 800 nm) of Arsenazo III; U(IV)-Arsenazo III; 
U(VI)-Arsenazo III; Zr(IV)-Arsenazo III; in HCl 3.6 mol L-1 media. GBC UV / VIS 918 
Spectrophotometry, cell with optical path length of 10 mm. 
 
 
3.2.  The Effect of the Acidity in the Intensity of the Absorbance Signal of Uranium 
 
 
Arsenazo III is a non-specific reagent for uranium [3], however, a high selectivity can be 
achieved for the U(IV) in strongly acidic medium (Figure 3) where only the thorium and 
zirconium react with the Arsenazo III. According to literature the optimal HCl concentration 
is 4 molL-1 [4] as demonstrated in Figure 3, but the application of such concentration can 
become complicated its use in the system of flow injection analysis proposed, because of the 
hydrogen gas release. In concentrations higher than 3.7 molL-1 the acid become to attack the 
lead used into the reduction column, releasing hydrogen gas. The gas, once formed, will be 
INAC 2013, Recife, PE, Brazil. 
 
entrained into the flow cell making a oscillating signal and impairment measurements. 
Therefore, we chose to work with a concentration of 3.6 molL-1. 
 
2,0 2,5 3,0 3,5 4,0 4,5 5,0
0,000
0,072
0,076
0,080
0,084
0,088
0,092
0,096
0,100
A
bs
o
rb
a
n
ce
HCl (molL-1)
 
Figure 3.  The effect of the acidity in the intensity of the absorbance signal of U(IV)-
Arsenazo III complex. Uranium concentration 0.5 mgL-1 and Arsenazo III 2.0 x 10-4 
molL-1, in HCl media. The measurements were carried out on a GBC UV / VIS 918 
spectrophotometry, at 665 nm with a cell optical path length of 10 mm. 
 
 
3.3.  Analytical Characteristics 
 
 
3.3.1.  Uranium determination 
 
 
For uranium concentration ranging between 0.05 and 2.0 mg L-1, the signal was found to be 
proportional to the uranium concentration and a straight line was obtained with a correlation 
coefficient (r) of 0.999 for the follow curve calibration: 
 
SU = (0.177[U]  ± 0.001) – (0.003 ± 0.001) (2)
 
Where SU is the absorbance signal measured, and [U] the unknown uranium concentration in 
mg L-1. Detection limit (DL: 3 σ criterion) and quantification limit (QL: 10 σ criterion) 
derived from 5 measurements of blank solution were 0.02 and 0.06 mg L-1, respectively. A 
Relative Standard Deviation (RSD) of 2.83 % at 0.10 mg L-1 was also derived from 5 
measurements of the solution. A sampling frequency of 30 h-1 was calculated, taking into 
consideration a time passed between two consecutive injections.  
INAC 2013, Recife, PE, Brazil. 
 
3.3.2.  Zirconium determination 
 
 
For zirconium concentration ranging between 0.2 and 1.0 mg L-1, the signal was found to be 
proportional to the zirconium concentration and a straight line was obtained with a 
correlation coefficient (r) of 0.995 for the follow curve calibration: 
 
S(Zr4+U6) = (0.220 )[Zr] ± 0.012 – (0.031 ± 0.008) (3)
 
Where S(Zr4+U6) is the absorbance signal measured when the sample or standard solutions 
passed though the reduction column, and [Zr] the unknown zirconium concentration in mgL-
1
. Detection limit (DL: 3 σ criterion) and quantification limit (QL: 10 σ criterion) derived 
from 5 measurements of blank solution were 0.052 and 0.102 mg L-1, respectively. A Relative 
Standard Deviation (RSD) of 1.98 % at 0.20 mg L-1 was also derived from 5 measurements of 
the solution. A sampling frequency of 30 h-1 was calculated, taking into consideration a time 
passed between two consecutive injections. 
 
 
3.4.  Application 
 
 
Table 1 and Table 2 show uranium and zirconium values for four samples (S1, S2, S3 and 
S4). S1, S2 and S3 are mix of standard solution with different proportions of uranium and 
zirconium. S4 are a pitchblende sample with an addition of uranium and zirconium standard 
solutions. The determinations were done by FIA-UVvis technique proposed. All were derived 
from 5 measurements. Analyzing the correlation between the values by the paired t-test, no 
sensible changing between the expected value and the observed value were noticed. The null 
hypothesis was retained the method proposed do not give significantly different values for 
means of uranium and zirconium concentrations. 
 
 
Table 1:  Uranium and zirconium determinations by the proposed method. 
 
 Expected Observed 
Sample U (mgL-1) Zr (mgL-1) U (mgL-1) Zr (mgL-1) 
S1 0.230 0.262 0.227±0.004 (1.8%) 0.253±0.004 (1.6%) 
S2 0.521 1.113 0.491±0.004 (0.8%) 1.121±0.023 (2.1%) 
S3 0.812 0.430 0.793±0.016 (2.0%) 0.431±0.008 (1.9%) 
S4 0.230 0.262 0.226±0.003 (1.3%) 0.251±0.006 (2.4%) 
Results are expressed as mean ± standard deviation (n = 5). Coefficient of variation is 
between parentheses. 
 
 
 
 
 
 
INAC 2013, Recife, PE, Brazil. 
 
Table 2:  Percentage difference between the concentrations of the observed and the 
expected values of uranium and zirconium obtained with the proposed method. 
 
 U (mgL-1) Dif. Zr (mgL-1) Dif. 
Sample Expected Observed % Expected Observed % 
S1 0.230 0.227 1.3 0.262 0.253 3.4 
S2 0.521 0.491 5.8 1.113 1.121 -0.7 
S3 0.812 0.793 2.3 0.430 0.431 -0.2 
S4 0.230 0.226 1.7 0.262 0.251 4.2 
 
 
4. CONCLUSIONS 
 
 
The proposed methodology developed, proved to be successful for uranium and zirconium 
determination in presence one of each other and no prior separation was needed. Comparison 
between the concentrations of the observed and the expected values for uranium and 
zirconium obtained with the proposed method demonstrated that there is no sensible 
changing. The proposed method can be used with minerals like pitchblende, since thorium is 
not present in its composition. The main advantages of the developed methodology are: the 
minimum sample treatment required, use of diluted acid, high sampling frequency (30 
samples h-1), lower sample amounts and possibility of automation of all analytical process. 
 
 
REFERENCES 
 
 
1. H. Perkampus, UV–Vis Spectroscopy and its Applications, Springer-Verlag, Berlin, 
Germany (1992) 
2. J. L P. Pavón, B. M. Cordero, J. H. Méndez, R. M. I. Agudo, “Application of Nested-Loop 
system for simultaneous determination of thorium and uranium by flow injection 
analysis,” Analytical Chemistry, 61, pp.1789-1791 (1989). 
3. P. N. Palei, Analytical Chemistry of Uranium, Ann Arbor-Humphrey Science Publishers, 
Inc., London, England (1970). 
4. S.B. Savvin, “Analytical use of arsenazo III – Determination of thorium, zirconium, 
uranium and rare earth elements,” Talanta, 8, pp.673-685 (1961). 


Determination of uranium and zirconium by flow injection analysis

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Determination of uranium and zirconium by flow injection analysis

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