Analytical Methods in Environmental Chemistry Journal Vol 1(2018) 5-10
Research Article, Issue 1
Analytical Methods in Environmental Chemistry Journal
Journal home page:
Solid phase extraction and determination of indium using
multi-walled carbon nanotubes modified with magnetic
Ehsan Zolfonoun a,*
a Material and Nuclear Fuel Research school, Nuclear Science and Technology Research Institute, Tehran, Iran
A R T I C L E I N F O:
Received 18 Aug 2018
In this work MWCNTs-Fe3O4 nanocomposite was used as an adsor-
bent for extraction and preconcentration of indium from aqueous so-
Revised form 20 Oct 2018
lutions. The magnetic MWCNTs with adsorbed analytes were easily
Accepted 28 Nov 2018
separated from the aqueous solution by applying an external magnetic
Available online 31 Dec 2018
field. After elution of the adsorbed analytes, the concentration of indi-
um was determined using inductively coupled plasma optical emission
spectrometry determination. The effects of pH, sorbent amount, eluent
type, chelating reagent concentration, sample volume, and time on the
recovery of the In(III) were investigated. Moreover, under the opti-
mum conditions, the detection limit for In(III) was 0.28 µg L−1. The
precision of the method, evaluated as the relative standard deviation
obtained by analyzing a series of ten replicates, was 3.1 %. Ultimately,
Carbon nanotubes
the method was successfully applied for the determination of In(III) in
Fe3O4 nanoparticles
.environmental water samples
1. Introduction
and biological samples. The quantification of metal
Indium is an important element in the semiconductor
ions in various matrices has been performed by
industry, in the nuclear studies and in the production
different techniques, including spectrophotometry,
of high purity materials
[1]. Indium and its
atomic absorption spectrometry
(AAS), and
compounds have numerous industrial applications
inductively coupled plasma optical emission
including the manufacture of liquid crystal displays
spectrometry (ICP-OES) [3]. In addition, using the
(LCD), semiconductors, low-temperature solders,
mentioned methods directly for determining indium
and infrared photodetectors
[2]. Also, indium
at very low concentrations is difficult because of
compounds damage the heart, kidney, and liver.
insufficient sensitivity of this technique, as well
Thus, there is a need for specific and precise
as the matrix interferences which occur in real
determination of indium traces in environmental
samples, and an initial sample pretreatment, such
as preconcentration of the analyses (or analytes)
*Corresponding author: Email:
and matrix separation, is often necessary [4]. Solid
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
phase extraction
(SPE) is a routine extraction
were used as supplied. HNO3, ammonia solution,
method for preconcentration of organic and
FeCl3·6H2O, and FeCl2·4H2O, were purchased
inorganic analytes. This technique reduces solvent
from Merck (Germany). MWCNTs (purity> 95%)
usage and exposure, disposal costs, and extraction
were obtained from Sigma-Aldrich. Standard stock
time. In addition, based on the references,
solution (1000 μg mL-1) of In(III) was prepared
and [6], various adsorbents have been used for
by dissolving appropriate amounts of In(NO3)3 in
adsorption of analytes in SPE methods.
water. A solution of 1.0×10−3 mol L−1 quinalizarine
Magnetic nanoparticles, mainly including Fe3O4
(Merck) was prepared by dissolving appropriate
nanoparticles, received increasing attention in the
amounts of this reagent in 0.01 mol L−1 NaOH
recent years due to its unique properties and high
potential applications in various fields such as cell
separation, magnetically assisted drug delivery,
2.2. Instrumentation
enzyme immobilization, and protein separation
All the measurements were carried out using a
[7, 8].. Recently, using magnetic nanoparticles for
Perkin Elmer
(Optima 7300 DV) simultaneous
extraction of analytes in SPE methods is gaining
ICP-OES coupled to a concentric nebulizer and
research interest [9, 10]. In addition, multi-walled
equipped with a charge coupled device (CCD)
carbon nanotubes
(MWCNTs) have received
detector. Moreover, Metrohm model 744 digital
great attention due to their exceptional electronic,
pH meter, equipped with a combined glass-
mechanical, thermal, chemical properties, and
calomel electrode, was employed for the pH
significant potential applications in many fields
[11]. Owing to their large surface area and high
reactivity, MWCNTs based adsorbents have been
2.3. Preparation of MWCNTs-Fe3O4 nanocomposite
used for solid phase extraction and preconcentration
MWCNTs-Fe3O4 nanocomposite was synthesized
of organic compounds and metal ions [12,13]. The
according to the previously reported methods,
decoration of MWCNTs with various compounds
which were mentioned in the references,
can modify their physicochemical properties. Also,
[15]. First, MWCNTs were dispersed in
this character makes them more suitable for chemical
concentrated nitric acid for 4 hours with ultrasonic
and biological applications. Functionalizing
treatment. Then purified MWCNTs were separated
MWCNTs with magnetic nanoparticles can
by filtering. Afterwards, they washed repeatedly
combine the features of magnetic nanoparticles
with distilled water followed by ethanol and dried
and MWCNTs, which may result in materials with
°C. The MWCNTs-Fe3O4 nanocomposite
potential applications in biological labelling, drug
was prepared by chemical coprecipitation method.
delivery, and magnetic storage media [14, 15]. In
First, FeCl3·6H2O (1.18 g) and FeCl2·4H2O (0.43
this paper, a magnetic solid phase extraction method
g) were dissolved in
200 mL deionized water
based on Multi-walled carbon nanotubes decorated
under nitrogen gas with vigorous stirring at 60
with Fe3O4 nanoparticles is developed for the
C. Then 1.0 gram of MWCNTs was added in the
extraction and preconcentration of trace amounts of
solution with ultrasonic treatment for about
indium, prior to their determination by ICP-OES.
min. Finally, NH4OH solution was added dropwise
into the solution until its pH was adjusted to 11.
2. Experimental Procedure
After stirring for 30 min at 50 °C, the obtained
2.1. Reagents
MWCNTs-Fe3O4 nanocomposite was separated
All reagents used were of analytical grade and
from the reaction medium by magnetic field, and
Solid phase extraction of indium; Ehsan Zolfonoun
washed with 200 mL deionized water four times.
The obtained results showed that by increasing the
sorbent amounts from 2 up to 5 mg due to increasing
2.4. Magnetic solid-phase extraction procedure
accessible sites, extraction recovery increased, and
A 100-mililiter sample or standard solution
then it remained constant. A 5-miligram of the
containing In(III)
6), and QA
MWCNTs-Fe3O4 nanocomposite was selected for
mol L−1), was transferred in a glassware beaker.
subsequent experiments.
Then 5 mg MWCNTs-Fe3O4 nanocomposite was
added into the sample solution. Afterwards, the
3.3. Effect of eluent type
mixture was stirred for 3 min. Subsequently, the
In order to find the best eluent, different eluting
sorbent particles were isolated by placing a strong
solutions such as HCl, H2SO4, HNO3 and acetic
magnet, and the supernatant was poured away. The
acid, were tested. The results revealed that a
preconcentrated target analyte was eluted using 1.0
1.0-mililiter of 1.0 M concentration of all acids
mL of a 1 mol L−1 solution of HNO3. Finally, the
could afford the quantitative elution of In3+ from
concentration of In(III) in acidic aqueous phase
the sorbent. Finally, subsequent elutions of In3+
was determined by ICP-OES.
were carried out with 1 M HNO3 solution
3. Results and discussion
3.4. Effect of chelating reagent concentration
3.1. Effect of pH
The effect of QA concentration on the extraction
The effect of pH on the extraction of indium was
of indium was studied, and the results are shown
studied in the range of 2.0-8.0 using nitric acid or
in Fig. 3. Also, QA concentration in the range of 0
sodium hydroxide. The resulting percent recovery-
to 5.0×10−5 mol L−1 was investigated by us. Then,
pH plots are shown in Fig. 1. These plots indicate
maximum recovery was obtained at a concentration
that sorption is maximum and quantitative in the
of 1.0×10−5 mol L−1 of the ligand and at higher
pH range of 6.0-7.0. Consequently, a solution pH
concentrations, the extraction recovery remained
of 6.0 was used in further experiments.
3.2. Effect of the sorbent amount
3.5. Effect of solution volume
In order to study the effect of the sorbent, 2 to
The effect of solution volume was examined by
10 mg of MWCNTs-Fe3O4 nanocomposite was
added to 100 mL of the sample solution (Fig. 2).
Fig. 2. Effect of the MWCNTs-Fe3O4
amount on the
Fig. 1. Effect of pH on the recovery of In(III) ion.
recovery of In(III) ion.
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
In(III) was studied in the range of 1-15 min. The
experimental results indicated that there was no
significant effect on the extraction efficiency when
the extraction time increased from 3 to 10 min.
Based on the above considerations, the extraction
time that is equal to 3 min was selected for further
3.7. Effect of diverse ions on the recovery
In order to assess the possible analytical applications
of the recommended procedure, the effect of
Fig. 3. Effect of chelating reagent concentration on the
common coexisting ions in natural water samples
recovery of In(III) ion.
on the preconcentration and determination of
indium ion was studied. In these experiments, 100
preconcentrating different volumes (20-250 mL)
mL solutions containing 50 μg L−1 of indium and
of aqueous solutions spiked with a constant mass
various amounts of interfering ions were treated
of 10.0 μg of In(III), and the results are depicted
according to the recommended procedure. In
in Fig. 4. The obtained results showed that when
addition, tolerable limit was defined as the highest
aqueous solution volume was up to
100 mL,
amount of foreign ions that produced an error not
recoveries above 95% were obtained. Thus, 100
exceeding ±5% in the determination of investigated
mL was considered to be the maximal enrichment
analyte ion. The results are summarized in Table
volume for water samples. Consequently, since the
1. As seen, a large number of ions used have no
final solution volume to be measured by ICP-OES
considerable effect on the determination of indium.
was 1.0 mL, the preconcentration factor for In(III)
was evaluated as 100.
3.8. Analytical figures of merit
In Table
2, the analytical characteristics of the
3.6. Effect of extraction time
proposed method, including linear range, limit
The effect of extraction time on the extraction of
of detection, reproducibility, and enrichment
factor have been summarized. In the optimum
conditions, a calibration graph was constructed by
preconcentrating a series of the solutions according
to the recommended procedure. There is an
important tip, that the calibration curve for In(III)
was linear form 1.0 to 500 µg L−1 with a regression
Table 1. Tolerance limits of some cations and anions on
the sorption and determination of indium.
Tolerance limit (µg mL−1)
Li+, Na+, K+, Cl-, NO3-
Ca2+, Mg2+, Ba2+, Sr2+
Ag+, Hg2+, SO4-
Cu2+, Fe3+, Pb2+, Ni2+, Co2+,
Fig. 4. Effect of sample volume on the recovery of
Cr3+, Mn2+, Cd2+, Zn2+
In(III) ion.
Solid phase extraction of indium; Ehsan Zolfonoun
Table 2. Analytical parameters of the proposed method.
Table 3. Recovery of indium from water samples.
Analytical feature
Linear range (µg L−1)
(µg L−1)
(µg L−1)
Tap water
LOD (µg L−1)
9.7 (1.8)a
R.S.D. % (n = 10)
Mineral water
Enrichment factor
River water
coefficient of 0.995. The limit of detection (LOD)
of the proposed method for the determination of
a Values in parentheses are R.S.D.s based on three
indium was studied under the optimal experimental
replicate analyses.
conditions. The LOD, defined three times by
paying attention to the standard deviation of 10
5. References
measurements of the blank solution divided by the
[1] M. Souad, C. Louage, J. Yves Doisy, L. Meunier,
A. Benderrag, B. Ouddane, S. Bellayer, N. Nuns,
slope of the calibration curve, was 0.28 µg L−1. The
M. Traisnel, U. Maschke, Extraction of indium-tin
reproducibility of the proposed method for extraction
oxide from end-of-life LCD panels using ultrasound
and determination of 50 µg L−1 indium (n= 10) was
assisted acid leaching, Ultrason. Sonochem., 40
also studied. Finally, the relative standard deviations
(2018) 929-936.
(R.S.D.) of these determinations were 3.1 %.
[2] J. Uhrovčík, J. Lesný, Determination of indium in
liquid crystal displays by flame atomic absorption
3.9. Application
spectrometry, J. Ind. Eng. Chem., 21 (2015) 163-
The accuracy of the proposed method was tested
[3] J.R. Dean, Practical inductively coupled plasma
by separation and determination of In(III) in tap
spectroscopy, Wiley., UK, 2005.
water, mineral water, and well water samples. The
[4] B. Çelik, E. Akkaya, S. Bakirdere, F. Aydin,
obtained results are given in Table 3. The relative
Determination of indium using vortex assisted solid
recoveries for the spiked samples were in the range
phase microextraction based on oleic acid coated
of 94-109 %. The results demonstrated that the
magnetic nanoparticles combined with slotted
proposed method was suitable for the determination
quartz tube-flame atomic absorption spectrometry,
Microchem. J., 141 (2018) 7-11.
of In(III) in real samples.
[5] M. Eftekhari, M. Gheibi, M. Akrami, F. Iranzad,
Solid-phase extraction of ultra-trace levels of
4. Conclusions
lead using tannic acid-coated graphene oxide as
In this study, a fast and simple method based was
an efficient adsorbent followed by electrothermal
developed for the separation and preconcentration
atomic absorption spectrometry; response surface
of indium, prior to ICP-OES determination. The use
methodology - central composite design, New J.
of NPs endued the SPE method with high extraction
Chem., 42 (2018) 1159-1168.
[6] J.B. Ghasemi and E. Zolfonoun, Simultaneous
capacity and preconcentration factors. The magnetic
spectrophotometric determination of trace amounts
separation greatly improved the separation rate while
of uranium, thorium, and zirconium using the partial
avoided the time-consuming column passing or
least squares method after their preconcentration by
filtration operation. The proposed preconcentration
α-benzoin oxime modified Amberlite XAD-2000
and determination method gives a low limit of
resin, Talanta, 80 (2010) 1191-1197.
detection and good R.S.D. values. Finally, the
[7] Y. Li, Y.C. Liu, and J. Tang, Fe3O4-Al2O3
method can be successfully applied to the separation
magnetic core-shell microspheres for rapid and
highly specific capture of phosphopeptides with
and determination of indium in real samples.
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
mass spectrometry analysis, J. Chromatogr. A,
applications,Science, 297 (2002) 787-792.
1172 (2007) 57-71.
[12] C. Herrero-Latorre, J. Barciela-García S. García-
[8] D. Horak, B. Rittich, J.A. Safar, A. Spanova, J.
Martín R. M. Peña-Crecente, Graphene and carbon
Lenfeld, and M.J. Benes, Properties of RNase A
nanotubes as solid phase extraction sorbents for
immobilized on magnetic poly(2-hydroxyethyl
the speciation of chromium: A review, Anal. Chim.
methacrylate) microspheres. Biotechnol. Prog., 17
Acta, 1002 (2018) 1-17.
(2001) 447-452.
[13] Z. Dehghani, Firouzabadi, S. Dadfarnia, A.M. Haji
[9] J.B. Ghasemi and E. Zolfonoun, Simultaneous
Shabani, M.H. Ehrampoush, E.N. Tafti, Magnetic
spectrophotometric determination of trace amount
dispersive solid phase extraction using modified
of polycyclic aromatic hydrocarbons in water
magnetic multi-walled carbon nanotubes combined
samples after magnetic solid-phase extraction
with electrothermal atomic absorption spectrometry
by using projection pursuit regression, Environ.
for the determination of selenium, Int. J. Environ.
Monit. Assess., 185 (2013) 2297-2305.
Anal. Chem., 98 (2018) 555-569.
[10] A. Mehdinia, M. Ramezani, A. Jabbari,
[14] A. Pistone, D. Iannazzo, and M. Fazio, Synthesis
Preconcentration and determination of lead ions
and magnetic properties of multiwalled carbon
in fish and mollusk tissues by nanocomposite of
nanotubes decorated with magnetite nanoparticles,
Fe3O4@graphene oxide@polyimide as a solid
Physica B, 435. (2014) 88-91.
phase extraction sorbent, Food Chem., 237 (2017)
[15] A. Masotti and A. Caporali, Preparation of Magnetic
Carbon Nanotubes (Mag-CNTs) for Biomedical
[11] R.H. Baughman, A.A. Zakhidov, and W.A.
and Biotechnological Applications, Int. J Mol. Sci.,
deHeer, Carbon nanotubes-the route toward
14 (2013) 24619-24642.