Electrochemical detection of atrazine in wastewater samples by copper oxide (CuO) nanoparticles ionic liquid modified electrode

Article abstract of DOI:10.1016/j.molliq.2017.10.085

In the present report, a new voltammetric sensor based on copper oxide nanoparticles involved in 2-(3-acetoxy-4-methoxybenzylidenamino)-thiophenol (AMT) ionic liquid (CuO NPs/ILs) was developed for atrazine (ATR) analysis. Firstly, the CuO NPs/ILs modifie

Full text of DOI:10.1016/j.molliq.2017.10.085

Accepted Manuscript
Electrochemical detection of atrazine in wastewater samples by
copper oxide (CuO) nanoparticles ionic liquid modified electrode
Faruk Kardaş, Murat Beytur, Onur Akyıldırım, Haydar Yüksek,
Mehmet Lütfi Yola, Necip Atar
PII:
S0167-7322(17)34189-2
doi:10.1016/j.molliq.2017.10.085
MOLLIQ 8047
DOI:
Reference:
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
11 September 2017
12 October 2017
18 October 2017
Please cite this article as: Faruk Kardaş, Murat Beytur, Onur Akyıldırım, Haydar Yüksek,
Mehmet Lütfi Yola, Necip Atar , Electrochemical detection of atrazine in wastewater
samples by copper oxide (CuO) nanoparticles ionic liquid modified electrode. The address
for the corresponding author was captured as affiliation for all authors. Please check if
appropriate. Molliq(2017), doi:10.1016/j.molliq.2017.10.085
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ACCEPTED MANUSCRIPT
Electrochemical Detection of Atrazine in Wastewater Samples by Copper Oxide (CuO)
Nanoparticles Ionic Liquid Modified Electrode
a
b
c
b
d*
e,
Faruk Kardaş , Murat Beytur , Onur Akyıldırım , Haydar Yüksek , Mehmet Lütfi Yola , Necip Atar *
a
Erzincan University, Faculty of Education, Department of Science Education, Erzincan, Turkey
b
Department of Chemistry, Faculty of Science and Letters, Kafkas University, Kars, Turkey
c
Department of Chemical Engineering, Faculty of Engineering and Architecture, Kafkas University, Kars,
Turkey
d
Iskenderun Technical University, Faculty of Engineering and Natural Sciences, Department of Biomedical
Engineering, Hatay, Turkey
e
Pamukkale University, Faculty of Engineering, Department of Chemical Engineering, Denizli, Turkey
∗Corresponding authors:
E-mail: necipatar@gmail.com (N. ATAR)
mehmetyola@gmail.com (M.L.YOLA)
0

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ABSTRACT
In the present report, a new voltammetric sensor based on copper oxide nanoparticles
involved in 2-(3-acetoxy-4-methoxybenzylidenamino)-thiophenol (AMT) ionic liquid (CuO
NPs/ILs) was developed for atrazine (ATR) analysis. Firstly, the CuO NPs/ILs modified
surface was investigated by using transmission electron microscopy (TEM), x-ray diffraction
(XRD), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and energy
dispersive x-ray analysis (EDX). The linearity range and the detection limit (LOD) of the
-11
-9
-12
prepared sensor were calculated as 1.0×10 – 2.0×10 and 2.0×10 M, respectively.
Voltammetric sensor was also applied to wastewater samples with high recovery.
Keywords: Atrazine; CuO nanoparticles; Ionic liquid; Square wave voltammetry
1

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1
. Introduction
The insects and some pests can be controlled by using the carcinogenic and cytotoxic
drugs. Nonetheless, many debris can come into the life chain such as water and food. Due to
these factors, the significant health and ecosystem problems emerge worldwide [1, 2]. ATR,
1
-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine, has triazine groups. It is one of the
most common pesticides [3, 4]. However, ATR as drug can be unconsciously used by
farmers. This situation causes the contamination of many water sources. Hence, the
environment and food chain adversely are affected [5]. Because of these reasons, early
analysis of ATR is needed in natural samples in terms of ecosystem and people. In the
literature, the methods such as gas chromatography–mass spectrometry [6], thin-layer
chromatography, high-performance liquid chromatography [7] and gas micellar electro kinetic
chromatography [8] were presented for this analysis. Nevertheless, when we want to
investigate these methods in terms of material consumption and expensiveness, there are
many negative situations. Due to these reasons, more sensitive, low-cost, simple and selective
sensors based on nanoparticles and nanomaterials are needed [9-12]. There are several reports
dealing with determination of ATR. The quartz crystal microbalance (QCM) technique was
developed based on ATR imprinted polymer [13]. However, the film decompositions on gold
chip frequently occur in comparison with carbon paste electrode. In addition, the expensive
electrodes such as gold were used for determination of ATR [14].
Ionic liquids have high conductivity. Because of this situation, they are promising
mediator in sensor applications [15, 16]. In addition, owing to high ionic conductivity, fast ion
mobility and ionic liquids can be used as electrolyte in the development of voltammetric
sensor [17-19].
The electrochemical detection of ATR has been not performed by CuO NPs/ILs up to
now. The novel electrochemical method based on CuO NPs/ILs was developed for selective
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and sensitive analysis. Firstly, CuO NPs/ILs nanomaterial was prepared. After that, CuO
NPs/ILs modified electrodes were developed. Finally, the electrodes were applied to
wastewater samples for ATR analysis.
2
. Experimental
2
.1. Materials
ATR was obtained from Sigma–Aldrich. The stock solutions of ATR (1.0 mM) were
prepared with 0.1 M phosphate buffer solution (PBS) (pH 7.0). Copper sulfate heptahydrate
CuSO .7H O], acetonitrile (MeCN), ethanol (EtOH), isopropyl alcohol (IPA), sodium
[
4
2
hydroxide (NaOH), liquid paraffin and graphite powder were purchased from Sigma–Aldrich
USA).
.2. Instrumentation
Electrochemical experiments were employed by IviumStat (U.S) equipped with C3
(
2
cell stand. JEOL 2100 HRTEM (JEOL Ltd., Tokyo, Japan) was utilized for the
characterization of nanocomposites. A Rigaku Miniflex X-ray diffractometer (Japan) using
monochromatic CuKα radiation was utilized for XRD.
2
.3. Synthesis of CuO nanoparticles
.5 M CuSO .7H O and 0.5 M NaOH were prepared in distilled water. The 0.5 M
0
4
2
o
NaOH solution put into the beaker. After that, it was heated to 60 C. The 0.5 M CuSO .7H O
4
2
solution was slowly added into the hot NaOH solution. After the precipitation, the mixture
o
was washed with distilled water and dried at 100 C for 10 h.
2
.4. Synthesis of AMT
-Hydroxy-4-methoxybenzaldehyde 1 (0.01 mol) was refluxed with acetic anhydride
20 mL) for 0.5 h. After pure EtOH (100 mL), the mixture was refluxed for 0.5 h. After
3
(
evaporation of the resulting solution at 40-45 °C, several recrystallizations of the residue from
EtOH gave pure compound 2 (3-acetoxy-4-methoxybenzaldehyde) [20]. 2-aminothiophenol
3

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(0.01 mol) was dissolved in acetic acid (20 mL) and treated with compound 2 (0.01 mol). The
mixture was refluxed for 2 h and then evaporated at 50-55 °C. After recrystallization, the
compound 4 (AMT) was obtained.
O
OH
OCCH3
O
C
O
C
H
OCH3
+
(CH CO) O
H
OCH3
3
2
-
CH COOH
3
1
2
O
SH
OCCH3
NH2
O
+
H
C
OCH3
3
2
AcOH -H O
2
O
OCCH3
SH
N=CH
OCH3
4
Scheme 1. Synthesis route of compound 4 (AMT)
.5. Electrode preparation
The used electrode in this study such as CuO NPs/ILs modified carbon paste electrode
CuO NPs/ILs/CPE) was developed according to the report [16].
.6. Sample preparation
The sample was prepared according to our previous protocol [21].
2
(
2
4

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3
. Results and discussion
3
.1. Characterization of nanostructures
The presence of CuO NPs on a lighter structure is seen clearly (Fig. 1A). The average
diameters of spherical CuO NPs as dark dots are 15-20 nm. Thus, this situation indicated that
CuO NPs was successfully prepared. In addition, the analysis of EDX confirms the formation
of CuO NPs. The Cu and O elements were observed in Fig. 1B.
Figure 1. (A) TEM image of CuO NPs and (B) EDX image of CuO NPs
Fig. 2 shows the XRD spectra of CuO NPs. the peaks indicated to the monoclinic
crystal system CuO NPs. The sharp structural peaks and crystallite size less than 50 nm shows
the nanocrystalline nature of CuO NPs.
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Figure 2. XRD spectra of CuO NPs
3
.2. Electrochemical studies
3
-
1
.0 mM [Fe(CN) ] was used for the characterizations of developed electrodes such as
6
bare CPE, CuO NPs/CPE, ILs/CPE and CuO NPs/ILs/CPE. The obvious reversible peaks of
3
-/4-
1
.0 mM [Fe(CN)6]
with 200 mV of peak potential difference (ΔEp) is seen at bare CPE
(curve a of Fig. 3A). After modification of CuO NPs on bare CPE, ΔEp decreased to 130 mV
with a small increase in the peak current (curve b of Fig. 3A). The more catalytic increase was
shown when ILs/CPE was used as working electrode (ΔEp = 80 mV on curve c of Fig. 3A).
Finally, when CuO NPs/ILs/CPE was used for working electrode, the more catalytic ability
and the less peak potential difference were obtained against redox probe (ΔEp = 40 mV on
curve d of Fig. 3A). The obtained results were confirmed by using EIS experiments. Fig. 3B
shows the impedance plot of (a) bare CPE (curve a), (b) CuO NPs/CPE (curve b), (c) ILs/CPE
(curve c) and (d) CuO NPs/ILs/CPE (curve d) surfaces. The obtained charge transfer
resistance (R ) values of the prepared electrodes are 135.0 ohm, 98.0 ohm, 73.0 and 48.0
ct
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ohm, respectively. According to Fig. 3A and Fig. 3B, R values are consistent with CV
ct
results.
Figure 3. (A) Cyclic voltammograms at (a) bare CPE, (b) CuO NPs/CPE, (c) ILs/CPE, (d)
CuO NPs/ILs/CPE; (B) EIS response at (a) bare CPE, (b) CuO NPs/CPE, (c) ILs/CPE, (d)
3
-
CuO NPs/ILs/CPE. Redox probe: 1.0 mM [Fe(CN) ] solution containing 0.1 M KCl, Scan
6
-1
rate: 100 mV s
3
.3. pH effect
The pH effect on ATR response was investigated in range of 3.0-9.0. The low and
high pH conditions caused the low current signal of ATR on modified electrode. The
protonation of ATR at the low pH and the ionic form of ATR at the high pH affected
negatively the extraction efficiency [21]. Thus, we selected 7.0 as optimum pH.
3
.4. Linearity range of proposed sensor
The square wave voltammograms (SWVs) of various concentrations of template
molecule (Fig. 4) indicate that the current increases linearly with ATR concentration. The five
measurements were performed for calibration graph. The regression equation (inset of Fig. 4)
is y (µA) = 5.6061x (nM) + 0.2121. Limit of quantification (LOQ) and LOD were obtained as
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1
.0×10 M and 2.0×10 M, respectively.
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Figure 4. SWVs of the CuO NPs/ILs/CPE (from blank solution without ATR to 2.0 nM ATR
in pH 7.0 of PBS) Inset: The calibration curves of ATR
3
.5. Recovery and Selectivity
The recovery was examined in wastewater samples (Table 1). As seen in the obtained
values, they are very close to 100.00%. According to the results, we can say that the CuO
NPs/ILs/CPE sensor in this report has high selectivity. In addition, to verify the high
selectivity, the standard addition technique was applied to the wastewater samples. The
obtained equation is y (µA) = 5.6098x (nM) + 7.937. Hence, the effect of interference from
wastewater sample was not importantly seen.
Table 1. Recovery of ATR in wastewater samples (n=6)
Sample
Added ATR
Found ATR
Recovery
(nM)
(nM)
(%)
Wastewater
-
1.73±(0.04)
-
0
.10
.20
.30
1.84(± 0.01)
1.91(± 0.02)
2.04(± 0.08)
100.55 ± 0.7
98.96 ± 0.3
100.49 ± 1.3
0
0
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3
.6. Reproducibility and stability of the CuO NPs/ILs/CPE
The six different electrodes were prepared with same procedure. For the obtained
current signals, the value of relative standard deviation is 0.37%. This situation shows the
fabrication reliability.
The stability of one electrode (CuO NPs/ILs/CPE) was examined. During 30 days, the
signal was frequently measured. The mean value is 99.17% of the first signal. The mean value
indicates that CuO NPs/ILs/CPE is utilized in long-term.
4
. Conclusions
In this report, a new electrochemical sensor was developed and applied for the
determination of atrazine in wastewater samples. According to the obtained data, the prepared
CuO NPs/ILs/CPE was well characterized by using TEM, EDX, EIS, CV and XRD. The
sensor shows high selectivity and sensitivity towards atrazine detection in wastewater matrix.
Because of these reasons, we can say that the electrochemical sensor was utilized for the
routine analysis without interference.
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Research Highlights
>
>
>
>
We developed a new electrochemical sensor for determination of atrazine
CuO nanoparticles ionic liquid nanocomposite was characterized
The voltammetric sensor was applied to wastewater samples
The developed nanosensor sensor might be preferred to the other analytical methods
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