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Journal of Smart Sensor and Materials, 2019, 1-26
Journal of Smart Sensor and Materials E-ISSN xxxx-xxxx
www.ukm.my/sensor
Issue: 1 Year: 2019
A Novel Electrochemical Detection Of Ochratoxin A In Cow Milk
Using Nickel
Nanoparticle Modified Electrode
by Suleiman Salihu, Nor Azah Yusof, and Jaafar Abdullah
A Low-Cost Tracking System for Running Race Applications Based
on Bluetooth
Low Energy Technology
by David Perez-Diaz-de-Cerio, Ángela Hernández-Solana, Antonio
Valdovinos and
Jose Luis Valenzuela
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Journal of Smart Sensor and Materials, 2019, 1-26
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EDITORIAL BOARD Journal of Smart Sensor and Materials Chief
Editor : Prof .Dr. Lee Yook Heng (Universiti Kebangsaan Malaysia)
Editor (Physical Sensor) : Assoc. Prof Dr. Mohd Kamarulzaki Mustafa
(Universiti Tun Hussein Onn Malaysia) Dr. Ruslinda A. Rahim
(Universiti Malaysia Perlis) Editor (Chemical Sensor/Biosensor) :
Prof. Dr. Nor Azah Yusof (Universiti Putra Malaysia) Assoc. Prof .
Dr. Siti Aishah Hasbullah (Universiti Kebangsaan Malaysia) Dr.
Jaafar Abdullah (Universiti Putra Malaysia) Dr. Tan Ling Ling
(Universiti Kebangsaan Malaysia) Dr. Faridah Salam (Institut
Penyelidikan dan Kemajuan Pertanian Malaysia) Dr. Sharina Abu
Hanifah (Universiti Kebangsaan Malaysia) Dr. Jahwarhar Izuan Abdul
Rashid (Universiti Pertahanan Nasional Malaysia) Editor (Sensing
Materials): Dr. Zainiharyati Mohd Zain (Universiti Teknologi MARA)
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Onn Malaysia) Managing Editor : Dr. Tan Ling Ling (Universiti
Kebangsaan Malaysia)
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Committee 2018/2019 Malaysian Society for Sensor Technology
Development
President : Assoc. Prof. Dr. Jaafar Abdullah Vice President :
Prof. Dr. Nor Azah Yusof Secretary : Dr. Jahwarhar Izuan Abdul
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Fairulnizal Md Noh Committee Assoc. Prof. Dr. Mohd Kamarulzaki
Mustafa Assoc. Prof. Dr. Zainiharyati Mohd Zain Assoc. Prof. Dr
Siti Aishah Hasbullah Dr. Sharina Abu Hanifah Dr. Nur Azura Mohd
Said Dr. Nurul Huda Abd Karim
The Malaysian Society for Sensor Technology Development serves
as a platform for all members and scientists to share their latest
findings in sensor research and also to strengthen and promote
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Society for Sensor Technology Development
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Journal of Smart Sensor and Materials, 2019, 1-26
Copyright: Malaysian Society for Sensor Technology Development,
2019
Journal of Smart Sensor and Materials
Issue 1 CONTENTS
1-26 Contoh: A NOVEL ELECTROCHEMICAL DETECTION OF
OCHRATOXIN A IN COW MILK USING NICKEL NANOPARTICLE
MODIFIED ELECTRODE
by Suleiman Salihu, Nor Azah Yusof, and Jaafar Abdullah
27-45 Contoh: A Low-Cost Tracking System for Running Race
Applications Based on Bluetooth Low Energy Technology
by David Perez-Diaz-de-Cerio, Ángela Hernández-Solana,
Antonio
Valdovinos and Jose Luis Valenzuela
-
Journal of Smart Sensor and Materials, 2019, 1-26
Objectives Journal of Smart Sensor and Materials provides a
forum for people working in the multidisciplinary fields of sensing
technology, and publishes contributions describing original work in
the experimental and theoretical fields, aimed at understanding
sensing technology, related materials, design development,
application of all sensors/biosensors, associated phenomena and
applied systems. Scope The scope of Journal of Smart Sensor and
Materials encompasses, but is not restricted to, the following
areas:- •Sensing principles and mechanisms •Materials for Sensor
Technology •Nanostructured materials •Synthetic organic chemistry
•Synthetic inorganic chemistry •Polymer composites •New sensing
transducers •Sensor fabrication technology •Actuators •Optical
sensors •Electrochemical sensors •Chemical sensors •Biosensors
•Physical sensors •Mass-sensitive devices •Gas sensors •Humidity
sensors •Lab-on-a-chip •Sensor-array •Optoelectronic sensors
•Mechanical sensors •Thermal sensors •Magnetic sensors •µTAS -
Micro Total Analysis Systems •Remote Sensing •Pressure Sensing
•Nuclear Sensing •Acoustic Sensing
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Journal of Smart Sensor and Materials, 2019, 1-26
A NOVEL ELECTROCHEMICAL DETECTION OF OCHRATOXIN A IN COW
MILK
USING NICKEL NANOPARTICLE MODIFIED ELECTRODE
Suleiman Salihu1, Nor Azah Yusof
1,2, and Jaafar Abdullah
1,2
1,1,2Department of Chemistry, Faculty of Science, Universiti
Putra Malaysia, 43400
Selangor, Malaysia.
**Corresponding author: email address: [email protected]
Abstract
A novel electrochemical sensor was fabricated for detection of
ochratoxin A in food samples by
synthesized nickel nanoparticle using
3-aminopropyltriethoxysilane as a cross linker. The
fabricated nanocomposite was homogenized in dimethylformamide
and drop casted on screen
printed electrode. The amine groups in APTES were used as growth
point for the NiNP synthesis
through electrostatic attraction between the amine group (NH4+)
and Ni(II) chloride
- while
sodium hydroxide acts as a reducing agent. Nickel nanoparticle
has good properties of
conductivity and catalytic particles that is intensively
exploited for electrode modification. The
Field emission scanning electron microscopy reveal that the
formed nanoparticle are dominantly
spherical in shape and evenly distributed. Field emission
scanning electron microscopy, energy
dispersive X-Ray, X-Ray diffraction and cyclic voltammetry were
used to characterize the
synthesized nanoparticle. The results show that the synthesized
nanoparticle induced a
remarkable synergetic effect for the oxidation of ochratoxin A.
Effects of some parameters, such
as pH, buffer, scan rate, accumulation potential, accumulation
time and amount of casted
nanoparticle, on the sensitivity of fabricated sensor were
optimized. Under the optimum
conditions, there is a linear calibration ranges from 0.1–0.5 µM
with equation of Ipa (µA) =
6.232 C (µM) + 0.9987, R2 = 0.998. The limit of detection and
limit of quantitation were
calculated as 0.00041 µM and 0.00135 µM respectively. The
fabricated electrochemical sensor
was successfully applied for determination of Ochratoxin A in
cow milk samples and all results
compared with high performance liquid chromatography (HPLC)
standard method.
mailto:[email protected]
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Journal of Smart Sensor and Materials, 2019, 1-26
Keywords: aminopropyltriethoxysilane; electrochemical sensor;
Ochratoxin A; nickel (II)
chloride, Nickel nanoparticle
Introduction
The most conventional methods used for detecting toxins in
foodstuffs are gas chromatography
with mass spectrometry (GC-MS) (Zhu et al., 2009, Mondello
2008), tandem mass spectrometry
(GC-MS/MS) (Mondello 2008), liquid chromatography with mass
spectrometry (LC-MS) or
tandem mass spectrometry (LC-MS/MS) (Bruins et al., 1987). These
analytical techniques have
the ability to detect target compounds down to the nanogram and
microgram per liter. Traditional
methods for detecting antibiotics include microbiological
inhibition tests, immunoassays, and
chemical physical methods such as gas/liquid chromatographic
(GC/LC) (Mondello 2008, Bruins
et al., 1987) analysis and capillary electrophoresis (CE) (Tong
et al., 2013). Ochratoxins belongs
to a group of mycotoxins produced as secondary metabolites by
several fungi of the Aspergillus
or Penicillium families and are weak organic acids consisting of
a derivative of an isocoumarin.
The family of ochratoxins consists of three members, A, B, and C
which are slightly different
from each other in chemical structures. These differences,
however, have marked effects on their
respective toxic potentials. Ochratoxin A (Fig.1) is the most
abundant and hence the most
commonly detected member but is also the most toxic of the three
(Van et al., 1965, Van der et
al., 1965). It is a potent toxin affecting mainly the kidney. As
in other mycotoxins, ochratoxin A
can contaminate a wide variety of foods due to fungal infection
in crops, in the field during
growth, at harvest time, in storage and in shipment under
favourable environmental conditions
especially when they are not properly dried. Ochratoxin A may be
present in a foodstuff even
when the visible mould is not seen.
Figure 1: Ochratoxin A
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Journal of Smart Sensor and Materials, 2019, 1-26
Ochratoxin A is found mainly in cereal and cereal products. This
group of commodities has been
reported to be the main contributors to ochratoxin A exposure in
exposure assessments carried
out by the European Commission (Jørgensen, 1997, Miraglia and
Brera, 2002, ), accounting for
50% of total dietary exposure of ochratoxin A in European
countries (SCOOP task 3.2.7, 2002).
Besides cereals and cereal products, ochratoxin A is also found
in a range of other food
commodities, including coffee, cocoa, wine, beer, pulses,
spices, dried fruits, grape juice, pig
kidney and other meat and meat products of non-ruminant animals
exposed to feedstuffs
contaminated with this mycotoxin. Ruminant animals such as cows
and sheep are generally
resistant to the effects of ochratoxin A due to hydrolysis to
the non-toxic metabolites by protozoa
in the stomachs before absorption into the blood (Kiessling
et.al., 1984). In ruminant animals like
cow, effective hydrolysis of ochratoxin A to the non-toxic
ochratoxin alpha takes place in the
four stomachs in the presence of the ruminant protozoa
(Kiessling et al., 1984) thus rendering the
species resistant to the effects of the toxin. Transfer to the
milk has been demonstrated in rats,
rabbits and humans. In contrast, little ochratoxin A is
transferred to the milk of ruminants, again
due to metabolism of this mycotoxin by the rumen microflora. The
main target site of ochratoxin A
toxicity is the renal proximal tubule, where it exerts cytotoxic
and carcinogenic effects. Ochratoxin A
has been reported to be an immune suppressor and affects the
immune system in a number of
mammalian species. It was able to cause inhibition of protein
biosynthesis and inhibition of
macrophage migration (Creppy et al., 1984). The European
Commission’s Scientific Committee
for Food (SCF), after reviewing its opinion on Ochratoxin A,
made its conclusion in 1998 that it
would be wise to reduce exposure to Ochratoxin A as much as
possible, ensuring that exposures
are towards the lower end of the range of tolerable daily
intakes which has been estimated by
other bodies, at a level below 5 ng/kg/day (De et al., 2016).
Studies on levels of Ochratoxin A in
food, so far, have been conducted mainly in the Western part of
the world. Consequentially,
international data accumulated at present are confined
principally to the Western diet. Little is
known about levels of Ochratoxin A with regards to the
rice-based Eastern diet pertaining to the
weather conditions in countries in the East.
Here we have reported a novel procedure for fabrication of
NiNP/SPE for electrochemical sensor
by electrode deposition process using polyvinypyrollidone as a
cross linker for detecting
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Journal of Smart Sensor and Materials, 2019, 1-26
Ochratoxin A in food. To the best of our knowledge, there is
little documented information on
the detection of ochratoxin A in food samples using NiNP//SPE
sensor.
Materials and Methods
All electrochemical measurements were carried out using a
portable potentiostat (DropSens,
mStat 8000, Spain) electrochemical system. The surface of the
working electrode, i.e. the screen-
printed carbon electrode (SPE, DropSens, Spain), was modified
with NiNP/aptes and connected
to the potentiostat using a USB connection. All characterization
studies on the morphology and
composition were investigated by field emission scanning
electron microscopy-energy dispersive
spectroscopy (FESEM-EDS, JEOL, USA) A pH meter (Fisher
Scientific, USA) was used to set
the pH values before each analysis.
3-aminopropyltriethoxysilane, and Nickel(II) chloride
hydrate (99.5%) were obtained from Aldrich (USA). All other
chemicals utilized in the research
were of analytical grade and used as received.
A 0.05 M acetate buffer (pH 5.1) was prepared by dissolving the
required amount of sodium
acetate in distilled and deionized water and the pH of the
solutions was adjusted by addition of
drops of acetic acid. Stock solutions of Ochratoxin A 1 x
10-3
M were prepared in distilled and
deionized water daily. The working solutions for the
voltammetric investigations were prepared
by dilution of the stock solution with aqueous buffer solutions.
All stock solutions were kept in
the dark and were used within several hours to avoid
decomposition.
All cyclic voltammetry (CV) measurements were performed in 1.00
mM K3Fe(CN)6 with 50 mM
KCl, while the differential pulse voltammetry (DPV) measurements
were carried out in 0.01M
phosphate buffered saline (PBS) with pH 7.4. The prepared 0.5M
of sulphuric acid (Sigma, St.
Louis, MO, USA) was used to activate the SPGE before
modification.
Electrochemical measurement
All electrochemical experiments were performed with a
three-electrode system at 25 °C. All
potentials were measured relative to the Ag/AgCl reference
electrode. Cyclic voltammetric scans
were performed at the potential range from -0.6 to +0.6 V at
scan rate of 0.1 V/s. The differential
pulse voltammetry measurements were performed at 0.6 V.
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Journal of Smart Sensor and Materials, 2019, 1-26
Results and Discussion
For the modified electrode, nickel nanoparticle was
electrochemically deposited on the screen
printed carbon electrode surface by cyclic voltammetry. The
nickel nanoparticle on modified
electrode were investigated using Zeta nanosizer, X-ray
diffraction and FESEM analysis. The
DLS analysis using the zeta potential of the sample was
determined with a Zetasizer Nano S90
(Malvern Instrument Ltd.) shows that the particle sizes in
aqueous solutions are in nanosize
range. The pure nickel nanoparticle in solution give an average
size value of approximately 15.1
nm. The DLS results places particles in nanorange while in
solution, and nanopowders were
dried for X-ray diffraction as shown in Fig.2. The broad
diffraction peaks are due to nanosize of
nanoparticle. Maximum intensity peaks (111) was used to estimate
the crystalline size and it is
found to be 15 nm using Scherrer equation. The surface
morphology of the unmodified and
modified screen printed carbon and the electrodeposited nickel
nanoparticle on SPCE surface are
shown in Figure 3. The result in the FESEM image, Fig.3
indicated that nickel nanoparticle were
electrodeposited on the screen printed carbon electrode surface
and were well distributed on the
surface with diameters in the range of 3 – 15 nm as confirmed by
X-ray diffraction in Fig.2. The
shape of Ni particle is spherical and are linked together to
form chains. X-ray diffraction analysis
was used to identify the phase and crystallinity of NP. The
synthesized NiNP showed diffraction
peak at 2θ angles of 44.5o, 51.8
o and 76.4
o, corresponding to crystal planes of 111, 200 and 222,
indicating face-centered cubical structure (Sudhasree et al.,
2014). FTIR spectroscopy is used to
study the interaction between different species and changes in
chemical composition of the
mixture. The IR spectra of NiNP synthesized is recorded in the
range of 400 - 4000 cm -1
. The IR
spectrum of NiNP synthesized shows the peaks at 3212.72,
1623.67, 1402.27, 1076.94, and 463
cm -1
correspond to O-H stretching which is the characteristic of
Ni(OH)2, the bond in CHC
suggests cross-linking of C-C formation, CH bending, CO stretch,
and NiO stretching,
respectively (Chanda et al., 2007, Sudhasree et al., 2014). The
calculated size values for NiNP
by Scherrer formula (Coates, G. W. 2000)) at 2θ of 44.5º is a
general approximate to those of
FESEM observation (Fig.3).
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Journal of Smart Sensor and Materials, 2019, 1-26
Figure 2: X-ray diffraction of Ni nanoparticle
Figure 3: The FESEM and EDX of NiNP.
Electrochemical behavior of the NiNP//SPCE
To study the electrochemical behavior, cyclic voltammograms of
ochratoxin A using
NiNP/SPCE were observed. The Fig.4 shows cyclic voltammograms of
the bare SPCE in 0.1 M
phosphate containing 10 µM ochratoxin A in the potential window
ranging from 0.0 to 1.0 V
with scan rate of 0.1 V/s. As shown in Fig.4, a pair of redox
peaks can be observed. with peak
currents of 0.5 mA and 10 mA because the effect of nickel
nanoparticle on the SPCE exhibits
high electrocatalytic activity towards ochratoxin A
detection.
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Journal of Smart Sensor and Materials, 2019, 1-26
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6-30
-20
-10
0
10
20
30
Cur
rent
(uA
)
Potential (V)
a
b
a = BareSPCE
b = NiNP/SPCE/
Figure 4: Cyclic voltammograms of the NiNP/SPCE in the absence
and presence of 10 µM
ochratoxin A in 0.1 M phosphate, at scan rate of 0.1 V/s
Fig.4 shows the cyclic voltammetry of modified and unmodified
SPEs in 0.1 mM K3Fe(CN)6 and
0.1 M HCl, with redox peaks in the potential range of -0.6 to
+0.6 V. The results shows lower
peak current for bare SPE (a) which is due to slow electron
transfer property of the electrode.
The peak current increases from 0.15 µA to 10 µA as NiNP was
used to modify the electrode (b),
which could be due to the effect of NiNP that enhanced
properties of electrode.
It was observed that peak current of 10 µA obtained with each
electrode increases with increase
in scan rate which is proportional to square of respective scan
rates, and this suggest diffusion-
control process (Zhang et al., 2013a). Active surface area of
bare and modified electrodes was
calculated according to Randles-Sevcik formula (Syrrokostas, et
al., 2012b, Chethana, and Naik
2012, Du et al., 2014)
𝑖𝑝 = (2.69 × 105)𝑛3/2𝐴𝐷1/2𝐶𝑣1/2
Where n is number of electrons participating in the redox
reaction, A is the surface area of
electrode (cm2), D is diffusion coefficient of molecules in
solution (7.6 x10
-6 cm
2 s
-1 ), C is the
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Journal of Smart Sensor and Materials, 2019, 1-26
concentration of K3Fe(CN)6 (M) and v is scan rate (Vs-1
). From slope of plot of Ipc vs v1/2
, the
surface area of electrodes can be calculated from using the
relation;
Aeff = 𝑆𝑙𝑜𝑝𝑒
2.69 𝑥 105 𝑛3/2 𝐷1/2 𝐶
As shown in Fig.4, the anodic current increases from bareSPE to
modified NiNP on the surface
which suggest that the modifying materials was successfully
deposited on the surface of the
SPCelectrode. The balanced redox reaction of K3[Fe(CN)6] in
(Tris-HCl and PBS) at the surface
of the electrode is given below:
K3[Fe(CN)6] + 3HCl 3K+ + [Fe(CN)6]
3- + 3H
+ + 3Cl
-
3KCl + 3H+ + [Fe(CN)6]
3- + e
- [Fe(CN)6]
4- + 3H
+
The deposition of nickel nanoparticle on the NiNP/SPE surface
induced a large reduction peak
current compared with bare SPE. There is migration of electron
to the electrode and accepted,
which led to the reduction of the oxidation number from +3 to
+2.
For bare SPE, the active surface area was calculated to be 0.034
cm2. While modification with
NiNP/SPE modified electrode has an increase in active surface
area of 0.084 cm2
(Figures not
shown). This suggests that nanoparticles have brought about an
increase in electro-active surface
area of SPE substrate.
To the electrochemical preparation of active and stable nickel
nanoparticle on the electrode
surface were conditioned by potential cycling from 0.0 to 0.6 V
at a scan rate of 0.1 V/s for 10
cycles.
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Journal of Smart Sensor and Materials, 2019, 1-26
The effect of supporting electrolytes
The supporting electrolyte plays vital role in electrochemical
detection of Ochratoxin A. In this
study as in Fig.5, four different buffers such as, phosphate
buffer, a mixture of monosodium
dihydrogen phosphate and disodium hydrogen phosphate, acetate
buffer, a mixture of sodium
acetate and acetic acid, citrate buffer a mixture of sodium
citrate and citric acid, and Britton
Robinson buffer a mixture of acetic, boric and phosphoric acid
of equal strength (0.1 M, pH 5)
were investigated and Fig.5 show results of influence of each
buffer solution towards
voltammetric oxidation of 10 µM Ochratoxin A. It was observed
that best results with respect to
shape and sensitivity are obtained in phosphate buffer solution
with peak current of 5.2 µA,
suggesting that it provided most favorable medium for
voltammetric oxidation of Ochratoxin A.
(a) (b)
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-40
-20
0
20
40
60
Cu
rre
nt (u
A)
Potential (V)
B
C
A
D
D
AcB
Figure 5: (a) CV and (b) Effect of supporting electrolytes on
voltammetric oxidation of Ochratoxin A of
10 µM in 0.1 M pH 4.0 (A) Acetate buffer (B) Britton Robinson
buffer (C) Citrate buffer (D) phosphate
buffer
0
1
2
3
4
5
6
A B C D
Cu
rre
nt
(µA
)
Supporting electrolytes
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Journal of Smart Sensor and Materials, 2019, 1-26
The effect of pH of supporting electrolytes were investigated.
Both peak potential and peak
current directly depends on pH of buffer solution. Results of
voltammetric response of 10 µM
Ochratoxin A at different pH range are presented in Fig.6. It
was found that oxidation of
Ochratoxin A in all pH ranges displayed voltammetric signals.
From results obtained, it shows
that as pH increases, peak current improved due to deprotonation
or loss of electron (Bagheri et
al., 2014). So, the protonated Ochratoxin A cannot properly
interact with working electrode
because of carboxylic groups that was attached to the surface of
the NiNP, consequently a lower
oxidation current is observed at lower pH (Rezaei and Damiri,
2010). Thus, best results with
respect to sensitivity and shape of voltammogram is obtained at
pH 6.0 with peak of 14.2 µA.
Therefore, 0.1 M phosphate buffer of pH 6.0 were chosen as
optimum medium for voltammetric
oxidation of Ochratoxin A at NiNP/SPE.
2 4 6 8 10
4
6
8
10
12
14
16
Cu
rre
nt
(uA
)
pH
Figure 6: Effect of pH on voltammetric oxidation of Ochratoxin A
at NiNP/SPE
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Journal of Smart Sensor and Materials, 2019, 1-26
The effect of accumulation potential on ochratoxin A
The detection potential is important for selectivity and
sensitivity of ochratoxin A
electrochemical sensor. Results of study of effect of Eacc on
voltammetric oxidation of ochratoxin
A shows that by varying Eacc from -0.6 to 0.4 V, in Fig.7 for
Ochratoxin A detections, peak
current of 14.8 µA increased steadily by varying the potential
between 0.2 to -0.4 V for Ochratoxin
A, due to reaction of their molecules which have more
adsorptivity on surface of modified
electrode within these range of values, conversely at negative
potentials lower than −0.4 V for
Ochratoxin A, peak current decreased, because at this potential,
layer of nanocomposite on surface
of SPE is unstable and therefore, hydrogen bubbles are produced
at the electrode which have
tendency to decrease sensitivity of electrode. Thus, the
potential of -0.4 V was chosen as the
detection potential in this work.
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0
0
5
10
15
20
25
30
35
40
Cu
rre
nt
(uA
)
Potential (V)
Figure 7: Effect of potential accumulation of Ochratoxin A on
electrode surface
The oxidation response of Ochratoxin A in connection with
accumulation time in Fig.8 was
investigated using cyclic voltammetry. Results of the influence
of accumulation time shows that
peak current increased with increase in accumulation time from
30 to 180 s as seen in Fig.8 for
Ochratoxin A, perhaps due to rapid adsorption of Ochratoxin A on
surface of electrode.
However, as oxidation peak current reaches 14.8 µA, it become
almost leveled off with further
increase in accumulation time beyond 180 s for Ochratoxin A.
This is could be due to saturation
of Ochratoxin A on surface of NiNP electrode (Pumera, 2010).
Thus, accumulation time of 180 s
was chosen as optimum value for the analysis.
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Journal of Smart Sensor and Materials, 2019, 1-26
Figure 8: Effect of accumulation time of Ochratoxin A on
electrode surface
The Fig.9 below shows CV of 10 µM Ochratoxin A on electrode
surface at different scan rate. It
was observed that as scan rate increases, oxidation peak current
of Ochratoxin A also increases
linearly and peak potentials shifted to more positive
potentials. A good linear relationship was
observed between oxidation peak current and scan rate (Fig. 10a)
under equations of Ipa =
76.527v + 1.032; 𝑅2 = 0.9856. The linear correlation, 𝑅2 =
0.9856 suggest that
electrochemical oxidation of Ochratoxin A at NiNP is under
adsorption control process. A plot
of log Ipavs log v, (Fig. 10b) also gives linear relationships
that are expressed as log (Ipa)(µA) =
3.318 log v(mV/s) - 0.7568; 𝑅2 = 0.9986. is typical of
adsorption control process also
confirmed that electrochemical oxidation of Ochratoxin A at NiNP
is under adsorption control.
Thus, it is concluded that voltammetric Oxidation of Ochratoxin
A at NiNP is under adsorption
control process.
0
2
4
6
8
10
12
14
16
0 50 100 150 200 250 300 350
Cu
rre
nt
(µA
)
taccumulation (s)
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Journal of Smart Sensor and Materials, 2019, 1-26
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-20
-10
0
10
20
Cu
rren
t (u
A)
Potential (V)
100 mV/s
10 mV/s
Figure 9: Cyclic voltammograms for the oxidation of 10 µM
Ochratoxin A on the surface of
NiNP in phosphate buffer (pH 6.0), accumulation potential -0.6 V
and accumulation time
180 s.
0
1
2
3
4
5
6
7
8
0.01 0.03 0.05 0.07 0.09 0.11
Ipa
(µA
)
Scan rate (V/s)
(a) y = 76.527x + 1.032
R2 = 0.9856
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Journal of Smart Sensor and Materials, 2019, 1-26
Figure 10: (a) Relationship between anodic peak current and scan
rate and (b) relationship
between log of peak current and log of scan rate on the
voltammetric oxidation of 10 µM
Ochratoxin A
To achieve higher sensitivity and lower background current, 100
mV/s is chosen as optimum
scan rate and used in further analyses.
To achieve higher sensitivity and lower background current, 100
mV/s is chosen as optimum
scan rate and used in further analyses.
The number of electrons involve in electrochemical oxidation of
Ochratoxin A at NiNP was
determined using equation below:
𝐼𝑝𝑎=𝑛𝐹𝑄𝑉
4𝑅𝑇
Where n is number of electrons transferred, F (C·mol−1
) is Faraday’s constant, Q (C) is quantity
of charge and v (V·s−1
) is scan rate. The value of n was estimated to be 0.798, which
suggested
that one electron is involved in electro-oxidation reaction.
Thus, it can also be concluded that
voltammetric reduction of Ochratoxin A, phosphate buffer (pH
6.0) at NiNP is accompanied by
loss of one electron.
0
0.5
1
1.5
2
2.5
3
0.1 0.15 0.2 0.25 0.3 0.35
Log
Ipa
Log v
(b) y = 3.318x + 2.031
R2 = 0.9986
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Journal of Smart Sensor and Materials, 2019, 1-26
It was also observed in scan rate studies that, as peak
potential keeps shifting to more positive
values with every increase in scan rate, a plot of Ep vs log v
yields a straight line with a slope that
can be expressed as 2.3 𝑅𝑇
(1−𝛼)𝑛𝐹 for oxidation peak current (Xu et al., 2018, Lawal,
2016), the
electron transfer coefficient (α) of electrochemical oxidation
of Ochratoxin A at electrode
surface was estimated to be 0.621 which suggests high electron
promotion process between
electrode surface and modifier towards oxidation of Ochratoxin A
(Xu et al., 2018).
The sensitivity of NiNP towards detection of Ochratoxin A was
investigated by differential pulse
voltammetry (DPV) under optimized experimental conditions for
different concentration of
Ochratoxin A in Fig.11. A linear relationship do exist between
peak current (Ipa) and Ochratoxin
A shows that peak height increases linearly with increase in
concentration of Ochratoxin A.
Figure 11: Differential pulse voltammetry for detection of
Ochratoxin A on the surface of
NiNP/SPE in phosphate buffer (pH 6.0), accumulation potential
-0.6 V, accumulation time
180s.
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Journal of Smart Sensor and Materials, 2019, 1-26
Figure 12: Calibration curve of the peak current versus
concentration of Ochratoxin A
under optimized experimental conditions.
Differential Pulse voltammograms of Ochratoxin A, Fig.11 clearly
show that plot of peak current
versus concentration is linear for 0.01 – 0.5 µM of Ochratoxin
A, the regression equation being
Ip(μA) = 6.232C + 0.9987 Ochratoxin A R2 = 0.9982), where C is
µM concentration of
Ochratoxin A and Ip is peak current. The limit of detection was
determined at 0.01 - 0.5 µM of
Ochratoxin A according to definition of YLOD = YB + 3σ (Gupta
and Kumar 1999), and found
to be 0.00041 µM while LOQ is 0.00135 µM.
The limit of detection (LOD) of developed electrochemical
sensors are calculated from a well
known equation (3σ/S) 10σ/S found in literature (Salih et al.,
2017, Janati et al., 2012, Sun et al.,
2012, Lavudu et al., 2013a), where σ is standard deviation of
measurements (n=5) and S is the
slope of linear regression equation of the plot of current
versus log[Ochratoxin A]. The linear
regression equation of the plots Fig.12 represent y = mx + C (x
is the concentration of
Ochratoxin A, y is the DPV peak current with nanoparticle.
Reproducibility of proposed sensor for Ochratoxin A detection
was evaluated by determining
Ochratoxin A (10 µM) with seven different electrodes freshly
prepared. They were used to
determined oxidation of anodic peak current, Ipa of 10 µM
Ochratoxin A contained in 0.1M
PBS, with the aid of cyclic voltammetry. Results in for
reproducibility show response with
0
2
4
6
8
10
12
14
0 0.5 1 1.5 2 2.5
Cu
rre
nt
(µA
)
Concentration (µM)
y = 6.232x + 0.9987
R2 = 0.9982
a
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Journal of Smart Sensor and Materials, 2019, 1-26
relative standard deviations of 1.92% using CV technique. The
result indicates a satisfactorily
regeneration of the modification procedure in the preparation of
NiNP/SPE with better
reproducibility and stability retaining 85% of its initial
signal suggesting good stability at room
temperature for the period of 28 days and therefore can be used
to determine Ochratoxin A. The
results obtained for interference (Table 1) under optimized
conditions indicate that interference
species have less than 5% peak currents in each analysis.
Table 1: The effect of some co-existing compounds on the
determination
of (10 µM) Ochratoxin A
Compounds Tolerancea
(mM)
Current change
%
Amoxicillin 50 +4.6
Penicillin G 50 +4.4
Thiamphenicol 50 +4.4
Sulfadiazine 100 +3.2
K+ 200 +4.4
Ca2+
200 -4.2
Na+ 200 +4.7
Mg(II) 200 -4.4
Zn(II) 200 -4.0
Mn(II) 200 -4.8
Fe(II) 200 -4.2
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Journal of Smart Sensor and Materials, 2019, 1-26
* aThe maximum mol ratio of each species that cause ≤5% change
in the determination of
Ochratoxin A.
The recovery study of Ochratoxin A were measured by spiking
Ochratoxin A free milk with
known amount of Ochratoxin A. The result shows drastic drop of
Ochratoxin A recovery which
could be due to high adsorption of the Ochratoxin A at the
surface of the electrode. The recovery
of the Ochratoxin A lies 72 to 99.2 %.
Detection of Ochratoxin A from real sample has been a crucial
challenge in the development of
electrochemical sensor technique. Extraction was carried out
according to (Tukiran et al., 2016,
Muhammad et al., 2018) method with little modification.
The applicability of the proposed sensor was evaluated by
analyzing Ochratoxin A in fresh milk
samples supplied. There was no peak current observed in Fig 11
(a) with milk sample indicating
that there is no traces of Ochratoxin A in the milk sample
supplied. The spiked sample of the
fresh milk with Ochratoxin A in Fig. 11 (b), shows current of
4.5 µA, 6.5 µA and 7.6 µA with
0.01 V, 0.02 V and 0.025 V while spiked sample with Ochratoxin A
in Fig.11 (c) shows current
of 1.48 µA, 2.7 µA and 6.9 µA with potentials of -0.02 V, 0.023
V and 0.01 respectively,
confirming the presence of Ochratoxin A in the spiked sample as
can be seen in Fig.11 (b) and
(c).
Conclusion
Applicability of the proposed NiNP electrochemical sensor for
detection of ochratoxin A in food
samples was determined. The results obtained with the developed
method were compared with
high performance liquid chromatographic (HPLC) technique. The
electrodeposited nickel
nanoparticle on the SPCE were simple, rapid, cost effective and
efficient. The proposed sensor
showed high sensitivity, low detection limit (LOD = 0.00041 μM,
LOQ = 0.00135 µM S/N=7)
and wide concentration range (0.01 to 2.0 µM). The linearity and
range are also similar as well
as their limit of detection and quantitation. These results
suggest that the developed sensor can
serve as alternative means of detecting ochratoxin A in food
samples
Acknowledgements
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Journal of Smart Sensor and Materials, 2019, 1-26
The authors acknowledge the Research grant No. 9443101 under
Prof. Dr. Nor Azah Yusof,
Department of Chemistry, Faculty of Science, Universiti Putra
Malaysia and also thank the
Faculty of Science.
References
Bagheri, H., Afkhami, A., Panahi, Y., Khoshsafar, H., &
Shirzadmehr, A. (2014). Facile
stripping voltammetric determination of haloperidol using a high
performance magnetite/
carbon nanotube paste electrode in pharmaceutical and biological
samples. Materials Science
and Engineering: C, 37, 264-270.
Bruins, A. P., Covey, T. R., & Henion, J. D. (1987). Ion
spray interface for combined
liquid chromatography/atmospheric pressure ionization mass
spectrometry. Analytical
Chemistry, 59(22), 2642- 2646.
Chanda, S. C., Manna, A., Vijayan, V., Nayak, P. K., Ashok, M.,
& Acharya, H. N. (2007).
PIXE & XRD analysis of nanocrystals of Fe, Ni and Fe2O3.
Materials letters, 61(28),
5059-5062.
Chethana, B. K., & Naik, Y. A. (2012). Electrochemical
oxidation and determination of
ascorbic acid present in natural fruit juices using a methionine
modified carbon paste
electrode. Analytical Methods, 4(11), 3754-3759.
Coates, G. W. (2000). Precise control of polyolefin
stereochemistry using single- site metal
catalysts. Chemical Reviews, 100(4), 1223-1252.
Creppy, E. E., Röschenthaler, R., & Dirheimer, G. (1984).
Inhibition of protein synthesis in
mice by ochratoxin A and its prevention by phenylalanine. Food
and chemical
toxicology, 22(11), 883-886.
De Nijs, M., Mengelers, M. J. B., Boon, P. E., Heyndrickx, E.,
Hoogenboom, L. A. P., Lopez,
P., & Mol, H. G. J. (2016). Strategies for estimating human
exposure to mycotoxins via
food. World Mycotoxin Journal, 9(5), 831-845.
Du, J., Yue, R., Ren, F., Yao, Z., Jiang, F., Yang, P., &
Du, Y. (2014). Novel graphene
flowers modified carbon fibers for simultaneous determination of
ascorbic acid, dopamine and
uric acid. Biosensors and bioelectronics, 53, 220-224.
Gupta, P., & Kumar, P. R. (1999). Critical power for
asymptotic connectivity in wireless
networks. In Stochastic analysis, control, optimization and
applications (pp. 547-566).
Birkhäuser, Boston, MA.
Janati, S. S. F., Beheshti, H. R., Asadi, M., Mihanparast, S.,
& Feizy, J. (2012). Preliminary
survey of aflatoxins and ochratoxin A in dried fruits from Iran.
Bulletin of environmental
contamination and toxicology, 88(3), 391-395.
Jørgensen, K. (1997). Assessment of dietary intake of ochratoxin
A by the population of EU
member States: SCOOP task 3.2. 2
Kiessling, K. H., Pettersson, H., Sandholm, K., & Olsen, M.
(1984). Metabolism of aflatoxin,
ochratoxin, zearalenone, and three trichothecenes by intact
rumen fluid, rumen fluid, rumen
protozoa, and rumen bacteria. Applied and Environmental
Microbiology.
Lavudu, P., Rani, A. P., & Sekaran, C. B. (2013).
Development and validation of HPLC method
for the determination of almotriptan malate in bulk and tablet
dosage forms. Int J Pharm
Tech Res, 5, 459-466.
-
Journal of Smart Sensor and Materials, 2019, 1-26
Lawal, A. T. (2016). Synthesis and utilization of carbon
nanotubes for fabrication of
electrochemical biosensors. Materials Research Bulletin, 73,
308-350.
Li, S., Marquardt, R.R, Frohlich, A.A., Vitti, T.G., and Crow,
G. (1997). Pharmacokinetics of
ochratoxin A and its metabolites in rats. Toxicology and Applied
Pharmacology 145:82.
Miraglia, M., & Brera, C. (2002). Assessment of dietary
intake of ochratoxin A by the
population of EU member states. Reports on tasks for scientific
cooperation. Reports of
experts participating in SCOOP Task, 3(7).
Mondello, L., Tranchida, P. Q., Dugo, P., & Dugo, G. (2008).
Comprehensive two‐dimensional gas chromatography‐mass spectrometry:
A review. Mass spectrometry reviews, 27(2), 101-124.
Muhammad, A., Hajian, R., Yusof, N. A., Shams, N., Abdullah, J.,
Woi, P. M., & Garmestani,
H. (2018). A screen printed carbon electrode modified with
carbon nanotubes and gold
nanoparticles as a sensitive electrochemical sensor for
determination of thiamphenicol residue
in milk. RSC Advances, 8(5), 2714-2722.
Pumera, M. (2010). Electrochemically powered self-propelled
electrophoretic
nanosubmarines. Nanoscale, 2(9), 1643-1649.
Rezaei, B., & Damiri, S. (2010). Fabrication of a
nanostructure thin film on the gold electrode
using continuous pulsed-potential technique and its application
for the electrocatalytic
determination of metronidazole. Electrochimica Acta, 55(5),
1801-1808.
Salih, F. E., Ouarzane, A., & El Rhazi, M. (2017).
Electrochemical detection of lead (II) at
bismuth/poly (1, 8-diaminonaphthalene) modified carbon paste
electrode. Arabian Journal of
Chemistry, 10(5), 596-603.
Sudhasree, S., Shakila Banu, A., Brindha, P., & Kurian, G.
A. (2014). Synthesis of nickel
nanoparticles by chemical and green route and their comparison
in respect to biological effect
and toxicity. Toxicological & Environmental Chemistry,
96(5), 743-754.
Sun, Y., Wang, M., Lin, G., Sun, S., Li, X., Qi, J., & Li,
J. (2012). Serum microRNA-155 as a
potential biomarker to track disease in breast cancer. PloS one,
7(10), e47003.
Syrrokostas, G., Siokou, A., Leftheriotis, G., & Yianoulis,
P. (2012b). Degradation
mechanisms of Pt counter electrodes for dye sensitized solar
cells. Solar Energy Materials and
Solar Cells, 103, 119- 127.
Tong, Y., Yin, X., Wang, Z., Zhan, F., Zhang, Y., Ye, J., ...
& Jiang, Y. (2013). A tailed primers
protocol to identify the association of eNOS gene variable
number of tandem repeats
polymorphism with ischemic stroke in Chinese Han population by
capillary
electrophoresis. Gene, 517(2), 218-223.
Tukiran, N. A., Ismail, A., Mustafa, S., & Hamid, M. (2016).
Determination of porcine gelatin
in edible bird's nest by competitive indirect ELISA based on
anti-peptide polyclonal
antibody. Food Control, 59, 561-566.
Van der Merwe, K.J., Steyn, P.S., and Fourie, L., Mycotoxins.
Part II (1965). The constitution of
ochratoxin A, B, C, metabolites of Aspergillus ochraceus Wilh.
Journal of the Chemical
Society 7038.
-
Journal of Smart Sensor and Materials, 2019, 1-26
Van der Merwe, K.J., Steyn, P.S., and Fourie, L., Scott, D.B.,
and Theron, J.J. (1965).
Ochratoxin A , a toxic metabolite produced by Aspergillus
ochraceus Wilh. Nature 205
(4976): 1112
Xu, J., Cao, Z., Zhang, Y., Yuan, Z., Lou, Z., Xu, X., &
Wang, X. (2018). A review of
functionalized carbon nanotubes and graphene for heavy metal
adsorption from water:
Preparation, application, and mechanism. Chemosphere, 195,
351-364.
Zhang, H., Xiao, R., Jin, B., Shen, D., Chen, R., & Xiao, G.
(2013a). Catalytic fast pyrolysis
of straw biomass in an internally interconnected fluidized bed
to produce aromatics and
olefins: effect of different catalysts. Bioresource technology,
137, 82-87.
Zhu, X., Wang, S., Liu, Q., Xu, Q., Xu, S., & Chen, H.
(2009). Determination of residues of
cyromazine and its metabolite, melamine, in animal-derived food
by gas chromatography−
mass spectrometry with derivatization. Journal of agricultural
and food chemistry, 57(23),
11075-11080.
The effect of supporting electrolytesThe effect of accumulation
potential on ochratoxin A