- Email: [email protected]
Impedimetric and stripping voltammetric determination of methamphetamine at gold nanoparticles-multiwalled carbon nanotubes modified screen printed electrode
Accepted Manuscript Title: Impedimetric and Stripping Voltammetric Determination of Methamphetamine at Gold Nanoparticles-Multiwalled Carbon Nanotubes Modified Screen Printed Electrode Author: Banafsheh Rafiee Ali Reza Fakhari Mohammad Ghaffarzadeh PII: DOI: Reference:
S0925-4005(15)00410-4 http://dx.doi.org/doi:10.1016/j.snb.2015.03.077 SNB 18271
To appear in:
Sensors and Actuators B
Received date: Revised date: Accepted date:
30-12-2014 26-3-2015 30-3-2015
Please cite this article as: B. Rafiee, A.R. Fakhari, M. Ghaffarzadeh, Impedimetric and Stripping Voltammetric Determination of Methamphetamine at Gold NanoparticlesMultiwalled Carbon Nanotubes Modified Screen Printed Electrode, Sensors and Actuators B: Chemical (2015), http://dx.doi.org/10.1016/j.snb.2015.03.077 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Highlights 1. SPE/MWCNTs-Nf/GNPs was used as a novel electrochemical sensor for quantitative detection of MA in alkaline solutions. 2. The MA oxidation has been investigated by SWASV and EIS owning high sensitivity.
ip t
3. The synergistic effect of MWCNTs and GNPs could greatly improve the electrode performance.
Ac ce
pt
ed
M
an
us
cr
4. Wide linear dynamic range, good reproducibility, high stability and fast response were the main advantages of the proposed impedimetric sensor.
1
Page 1 of 42
Impedimetric and Stripping Voltammetric Determination of Methamphetamine at Gold Nanoparticles-Multiwalled Carbon
*
cr
Banafsheh Rafiee and Ali Reza Fakhari
ip t
Nanotubes Modified Screen Printed Electrode
Department of Chemistry, Faculty of Sciences, Shahid Beheshti University, G. C., PO Box 19396-4716,
Ac ce
pt
ed
M
an
us
Tehran, Iran
*
Corresponding author, Tel.: +98 21 22431661; fax: +98 21 22431683. E-mail address: [email protected] (A.R. Fakhari).
2
Page 2 of 42
Abstract
ip t
A high performance electrochemical sensor for the detection of methamphetamine (MA) at the gold nanoparticle (GNP)/multiwalled carbon nanotube (MWCNT)-Nafion (Nf) modified screen
cr
printed electrode (SPE) is reported. Gold nanoparticles were electrodeposited on the substrate using a constant potential. Energy dispersive X-ray (EDX) spectrum and mapping and also
us
scanning electron microscopy (SEM) results showed that GNPs were deposited and dispersed
an
uniformly on the SPE/MWCNTs-Nf-Nf, respectively. The electrochemical behavior of MA was studied by cyclic voltammetry (CV), and modified electrode was used for the determination of
M
sub-nanomolar amounts of MA in samples using square wave stripping voltammetry (SWSV) and electrochemical impedance spectroscopy (EIS). Under the optimized experimental
ed
conditions, the modified SPE revealed broad linear ranges of 0.02–0.1 and 3.0–50 µM (LOD = 6 nM) for SWSV and 1.15–26.9 nM (LOD = 0.3 nM) for EIS. Finally, the SPE/MWCNTs-
pt
Nf/GNPs showed stable electrochemical cyclic voltammetry responses. The high performances of the novel MA impedimetric sensor are mainly attributed to high surface area-to-volume ratio,
Ac ce
excellent conducting capability and interface-dominated properties of GNPs which in combination with special properties of MWCNTs provide an effective modifier for MA oxidation. Moreover, using sensitive methods like impedimetric and stripping results in excellent responses.
Keywords: Methamphetamine; Impedimetric sensor; Anodic stripping voltammetry; Gold Nanoparticles; Screen Printed Electrode; MWCNTs 3
Page 3 of 42
1. Introduction Methamphetamine (MA) (Scheme 1) is a powerful central nervous system stimulant [1] that
ip t
brings about wakefulness and anorexia [2] and is abused in many countries [3]. It produces a rapid pleasurable feeling, which is followed by feelings of depression and irritability when the
us
cr
drug wears off.
an
Scheme 1. Structural formula of methamphetamine.
The drug is available as water soluble white crystalline form. Pure methamphetamine, the
M
smokable form of the drug, is called “glass”, “ice”, “crystal” or “quartz” because of its clear, chunky crystals which resemble frozen water. Despite warnings of irreversible damage to the
ed
central nervous system due to its consumption (even strokes and death), enhancement the abuse
pt
of this drug (especially among the young generation) is causing an increase in cost and crime and finally serious social problems in many countries [4, 5]. One reason might be the ease of
Ac ce
synthesis from readily available raw materials, which brings lots of money for sellers and smugglers [6]. Therefore, there is a great interest for the quantitative analysis of such drugs by an inexpensive and powerful method in forensic as well as clinical laboratories. Several methods have been introduced for this purpose like gas chromatography (GC) [7], GC–mass spectrometry (GC–MS) [8], high-performance liquid chromatography (HPLC) [6], HPLC–tandem mass spectrometry (LC/MS/MS) [9], electrochemiluminescence (ECL) [10], immunoassay [11], Ion mobility spectrometry (IMS) [12] and capillary electrophoresis (CE) [13]. Although these methods are accurate but they suffer from problems of time-consuming, laborious operations and 4
Page 4 of 42
expensive apparatuses. Furthermore, they need several preparation steps before main procedure. Therefore, a simple, fast and accurate method is necessary for routine analysis and detecting MA in samples. Electrochemical detection is a simple and inexpensive method and also is attractive
ip t
as it can provide sensitivity and reduces analysis time to enable continuous real-time measurements compared to the above methodologies. To our knowledge, electrochemical
cr
method has scarcely been applied to determine MA. Our findings show that there is just one
us
report for electrochemical study of MA which the authors have investigated the electrochemical behavior of MA at a glassy carbon electrode [14].
an
In electrochemical analysis, the key component is electrode modification, which requires the selection of suitable material to improve the determination performance [15]. In principle, the
M
electroanalytical detection limit at a nanoelectrode can be much lower than that at an analogous macrosized electrode because the ratio between the faradic and capacitive currents is higher [16].
ed
Carbon nanotubes (CNTs) have attracted much attention due to their special properties [17-19].
pt
As electrode modifiers, CNTs show negligible surface fouling [20], decreased overpotential and increased voltammetric currents. Indeed, CNT electrode is driving the electron transfer reaction
Ac ce
faster than many other carbon electrodes surfaces observed, with very small apparent activation barrier at the electrode surface [21]. Nanosized particles of noble metals, especially gold nanoparticles (GNPs), have received great interests due to their high surface area-to-volume ratio, excellent conducting capability, excellent biocompatibility and their interface-dominated properties. Anodic stripping voltammetry (ASV) has been recognized as a powerful technique for electrochemical measurements of trace analytes in which a preconcentration step is combined with a stripping step, thereby enhancing the sensitivity [22]. When square-wave voltammetry 5
Page 5 of 42
(SWV) is employed for anodic stripping, the resulting method of square wave anodic stripping voltammetry (SWASV) offers many advantages over the more popular methods like differentialpulse ASV (DPASV) [23-25].
ip t
Electrochemical impedance spectroscopy (EIS) is a rapidly developing technique for the study of sensing events at the surface of an electrode [26] and is widely used in different fields’ studies
cr
[27-33]. Faradic impedimetric systems are based on measuring the charge transfer resistance of a
us
redox probe at an electrode interface. Impedance detection has been found to be sensitive, rapid and can detect at very low concentration reaching a limit of detection of 10−18 M in some cases
an
[34]. Moreover, the measurement does not have any specific prerequisites (e.g., labels or electroactive moieties in the molecule) [35]. carbon
electrodes
(SPEs)
represent
a
widely
accessible,
disposable
M
Screen-printed
electrochemical sensor, simple, inexpensive and non-toxic [36]. Replacement of conventional
ed
electrochemical cells by SPEs connected to miniaturized potentiostats is a main trend in the shift of lab electrochemical equipments to hand-held field analyzers [37]. They are also suitable for
pt
working with microvolumes and for decentralized assays (point of care tests), etc.
Ac ce
The main goal of this work is to investigate the electrochemical response of MA on the surface of SPE/MWCNTs-Nf-Nf/GNPs and develop a novel electrochemical sensor for quantitative detection of MA in forensic or clinical samples. For this purpose, MA was determined by SWASV. We have also reported the impedimetric detection to have comprehensive investigation of MA oxidation at this modified electrode. To the best of the author’s knowledge, this study presents the first ever electrochemical detection of MA with this type of nano-modified electrodes.
6
Page 6 of 42
2. Experimental 2.1. Chemicals and materials
ip t
Multiwalled carbon nanotubes with purity 95% (20‒40 nm diameter and 1‒10 µm length) were obtained from Research Institute of Petroleum Industry (Tehran, Iran). MA, as the hydrochloride
cr
salt, was purchased from Dr Ghaffarzadeh (Institute of Chemistry and Chemical Engineering).
us
Nafion 5% solution was purchased from Sigma. All other solvents and reagents were purchased from Aldrich or Merck and were used without further purification. A stock solution of MA (0.10
an
M) was prepared by dissolving MA in deionized water. MA solutions were prepared by diluting aliquots of the MA stock solutions with a carrier solution and were freshly prepared just prior to
M
use. All other solutions were prepared with doubly distilled water. All experiments were carried
pt
2.2. Instruments
ed
out at room temperature.
Ac ce
All electrochemical experiments were performed using Autolab potentiostat/galvanostat type 30 (2) (Eco Chemie, Netherlands), equipped with FRA and GPES 4.9 software. Screen-printed carbon electrode (SPE) (3.0 mm in diameter) from Dropsens (Spain) was used as a planar three electrode based on a graphite working electrode, a carbon counter electrode and a silver pseudoreference electrode. The electrode was rinsed in deionized water and preconditioned in 0.10 M HCl solution by potential scanning in –0.3 to +1.3 V at a scan rate of 100 mV s-1. The following parameters were employed for CV and SWASV, respectively: CV: scan rate 50 mV s-1 and MA solution of 5.0 mM; SWASV: pulse amplitude 10 mV, pulse width 10 ms and MA solution of 7
Page 7 of 42
0.1 mM. EIS experiments carried out with a dc-offset potential of 280 mV and in the frequency range of 100000 to 0.01 Hz. Scanning electron microscopy (SEM) images, were obtained using KYKY-EM3200 SEM and energy dispersive X-ray (EDX) spectrum and EDX mapping were
ip t
obtained using Philips XL-30 ESEM.
cr
2.3. Preparation of modified electrode
us
MWCNTs were stirred in concentrated HNO3 for 6h and then refluxed in the mixture of concentrated H2SO4:HNO3 (3:1) for 24 h to obtain the carboxylated multi-walled carbon
an
nanotubes [36]. The MWCNTs were washed with doubly distilled water and dried in vacuum at 80 ºC. Carboxylated MWCNTs (10.0 mg) and 5.0 µl of 5% nafion solution were dispersed in 5.0
M
ml water with ultrasonication for 1 h to get a homogenous suspension. The SPE/MWCNTs-Nf was prepared by casting 10.0 µl of the suspension onto the surface of screen printed electrode
ed
and let to evaporate to dryness at room temperature. The electrodeposition of gold nanoparticles on SPE/MWCNTs-Nf was conducted using a constant potential. The characteristic of gold
pt
deposition on the electrode surface is strongly influenced by several parameters: the two most
Ac ce
important being the HAuClO4 concentration and the deposition time [38]. Both factors have been optimized and the constant potential of −400 mV versus Ag was applied on these electrodes for a period of 30 seconds in 0.10 M HCl solution containing 10.0 mM HAuCl4 [39].
3. Results and discussion 3.1. Structures characterization
8
Page 8 of 42
The surface morphology and nanostructure of the screen printed electrode/carboxylated multiwalled carbon nanotube/gold nanoparticles (SPE/MWCNTs-Nf/GNPs) was characterized
ip t
by SEM and EDX techniques.
cr
3.1.1. SEM results
us
Fig. 1 shows the SEM images of the SPE surface modified with MWCNTs-Nf (A) and MWCNTs-Nf/GNPs (B). As shown in this figure, a network-like structure of MWCNTs without
an
aggregation was observed on the SPE surface which suggested that the MWCNTs were immobilized on the SPE surface. The diameter of the MWCNTs was about 14 – 40 nm. This
M
figure also shows gold nanoparticles electrodeposited onto the SPE/MWCNTs-Nf. White spots in the SEM images present gold nanoparticles which are distributed uniform and dense on the
ed
SPE/MWCNTs-Nf. The particle dimensions are in the range of 17 – 40 nm. A volume array of MWCNTs ensures a uniform spatial distribution and storage of gold nanoparticles, while
pt
remaining highly permeable for a flow of liquid or gas (not presenting large hydrodynamic
Ac ce
resistance in contrast to compacted powders) [40], providing an increased sensing area and effective mass transportation pathway [41].
3.1.2. EDX spectrum
Fig. 1C shows the EDX spectrum of the composites. The element of C in the EDX spectrum is basically from the MWCNTs-Nf. The presence of gold signals in the spectrum suggested the
9
Page 9 of 42
nanocomposite contained gold particles. Consequently, the presence of gold nanoparticles on the SPE/MWCNTs-Nf which was shown by SEM images was confirmed by EDX technique.
ip t
Figure 1 3.1.3. EDX mapping
cr
EDX mapping provides, in addition to the conventional SEM image, a meaningful picture of the
us
element distribution of a surface. Fig. 2 shows the SEM image and EDX mapping of SPE/MWCNTs-Nf/GNPs surface. The color represents the type of element, and the darkness
an
reflects the element's concentration. As shown in this figure, the distribution of carbon is quite concentrated, which indicates that the majority of the modified layer was MWCNTs. Moreover,
M
the EDX mapping (c), clearly shows that gold nanoparticles are distributed highly uniform on the
ed
modified electrode surface.
Ac ce
pt
Figure 2
3.2. Cyclic voltammetric response of the MWCNTs/GNPs modified SPE in MA solution As an initial test for the performance of modified electrode in MA oxidation, cyclic voltammograms of three electrodes in 0.01 M NaOH solution containing 0.01 M MA with a scan rate of 100 mV s–1 were compared and the results are exhibited in Fig. 3. The MA oxidation potential peak was seen at about Ep = 0.45 V. The appearance of a peak at this Ep value resulting from the oxidation of aliphatic secondary amines has also been described in the literature for
10
Page 10 of 42
other aliphatic amines [42,43] and as mentioned in previous work, MA is oxidized in aqueous electrolytes through a one electron transfer followed by a chemical reaction (EC mechanism). The chemical reaction is fast enough for the reduction of the cation radical not to occur in the
cr
reverse scan, indicating an irreversible reaction for MA oxidation.
ip t
time scale of voltammetry [44]. The cyclic voltammogram shows no reduction peak in the
us
Figure 3 Furthermore, cyclic voltammograms of SPE/MWCNTs-Nf/GNPs in solutions of different pH
an
values containing 5.0 mM MA in the potential range of 0 – 1200 mV versus Ag and with a scan rate of 50 mVs−1 were taken. Over the entire pH range examined (2 – 12), a single anodic peak
M
was observed. The highest current peak was observed at pH 12, therefore 0.01 M NaOH solution was used in other experiments as electrolyte solution. In spite of most of the electrochemical
ed
studies with gold nano particles which have done in acidic medias [45, 46], for the proposed electrode peak current of MA oxidation in NaOH solution was much higher than in acidic one. It
pt
can be explained by this fact that the MA secondary amine group is more easily oxidized in basic solution than in acidic solution, and this data correlates well with the pKa = 10.1 of the amine
Ac ce
function of MA [14].
3.3. The effect of scan rate on the electrochemical behavior Cyclic voltammograms in Fig. 4A are shown for different scan rates from 1 – 200 mV s−1 in 0.01 M NaOH solution in the presence of 5.0 mM MA. The experiment result shows that the MA oxidation peak current increases linearly with the sweep rates in the range of 1 – 200 mV s-1 (y =
11
Page 11 of 42
1.0667x + 9.1664) and with a correlation coefficient of 0.997 (Fig. 4B). This means that the electrocatalytic reaction of MA is an adsorption-controlled process at the modified electrode. Moreover, the oxidation potential shifts positively from 409 to 482 mV. It is known that for the
ip t
reversible electrode reaction, the oxidation peak potential is independent of scan rate [47]. Therefore existence of oxidation potential shift represents a kinetic limitation in the reaction
us
cr
between the active sites and MA.
an
Figure 4 Plotting the Epa vs. logν produces a straight line with a slope of 0.2796 which is shown in Fig. 4C.
M
According to Laviron’s equation [48], the slop is equal to b/2 and b = 2.303RT/(1 − α) nαF.
ed
Laviron derived general expressions for the linear potential sweep voltammetric response of electroactive species at small concentrations [48]. The expressions for peak-to-peak potential
Ac ce
pt
separations of ΔEp > 200/n mV, where n is the number of exchanged electrons, are as follows:
(1) (2)
where X = RT / (1-αs) nF, Y = RT / αnF, m = (RT/F) (ks/nν), Epa is the anodic peak potential and αs, ks, and ν are the electron-transfer coefficient, apparent charge-transfer rate constant, and potential scan rate, respectively. From these expressions, as can be determined by measuring the
12
Page 12 of 42
variation of the peak potential with respect to the potential scan rate, and ks can be determined for electron transfer between the electrode and the surface-deposited layer by measuring the ΔEp values. According to Fig. 4C, it could be observed that for potential scan rates of 100 to 400 mV
ip t
s-1, Ep and logv present a good linear relationship. The values of Ep are proportional to the logarithm of the potential sweep rate showed by Laviron. Use of the plot and Eqs. (1) and (2),
cr
the value of αs,a (anodic electron-transfer coefficient) was determined to be 0.78. Moreover, the
us
mean value of ks was determined to be 0.44 s-1.
The Tafel plot derived from the rising part of a voltammogram recorded for MA oxidation at a
an
scan rate of 1 mV s–1 and the plot is exhibited in Fig. 4D. The Tafel equation for anodic reactions
log I = log I0 + (1–
nF/2.303 RTE
M
is:
(3)
ed
This plot gives a Tafel slope of 4.64 V. Assuming a “one electron transfer” to be rate limiting step, a value of 0.73 was obtained for the charge transfer coefficient of the catalytic reaction, αn
Ac ce
pt
= 0.73.
3.4. Study of electrochemical behavior of MA at SPE/MWCNTs-Nf/GNPs by SWASV Since CV was not sensitive for the determination of low contents of compounds, SWV studies were performed. The SWASVs were recorded at different modified screen printed electrodes. Fig. 5 shows the results obtained by SWASV at the bare SPE (a), SPE/MWCNTs-Nf (b), SPE/MWCNTs-Nf/GNPs (c) and SPE/MWCNTs-Nf/GNPs after using –200 mV for 200 s as stripping step (d) in 0.01 M NaOH solution containing 0.1 mM MA.
Figure 13 5
Page 13 of 42
ip t
It can be seen that the currents at the bare screen printed carbon electrode and SPE modified with MWCNTs-Nf are negligible. In the presence of gold nanoparticles at the modifier layer, the
cr
oxidation current increases significantly so that a well-defined oxidation peak can be observed at a potential about 280 mV (curve c). The coverage of the GNPs on the carbon nanotubes is such
us
that the nanotubes themselves can simply be considered as a high area support and the
an
electroactivity arises solely from the GNPs [49].
At curve (d) the modifier layer is the same as the modifier layer at curve (c), the only difference
M
is the potential used (–200 mV for 200 s) before MA oxidation as stripping step which accumulate the analyte prior to the oxidation. As can be seen, this electrode exhibited the
ed
sharpest and the highest signal compared to the others for 0.1 mM MA solution. Because the MWCNTs-Nf/GNPs nanocomposites were employed by taking advantage of its specific affinity
pt
of the nitrogen to gold nanoparticles and fast electron transfer rate of MWCNTs, on the other
Ac ce
hand, owing to the special physicochemical properties of nanomaterials, they can obviously improve the sensitivity and selectivity of stripping voltammetry techniques [50]. Therefore, using MWCNTs and gold nanoparticles as modifier layer and –200 mV potential for anodic stripping voltammetry are the best conditions for MA detection at the SPE in the 0.01 M NaOH solution by SWASV.
3.4.1. Optimization of conditions for the SWASV
14
Page 14 of 42
The observed stripping peak of MA at MWCNTs-Nf/GNPs modified SPE is strongly affected by parameters such as Edep, and tdep.
ip t
3.4.1.1. Effect of deposition potential (Edep) The effect of electrodeposition potential was investigated for a fixed period of time, in the
cr
presence of 0.1 mM MA at different applied potentials (+100, 0, −100, −200, −300, −400 mV).
us
Fig. 6 shows the stripping currents. The results indicated that the optimum deposition potential
an
was −200 mV under this condition.
3.4.1.2. Effect of deposition time (tdep)
M
Figure 6
ed
The effect of the deposition time on the peak current of 0.1 mM MA has been also studied in the range from 0 to 350 s and the results are exhibited in Fig. 7. The results indicated that the peak
pt
current increased from 0 up to 200 s. This is because more and more MA accumulated on the
Ac ce
surface of the SPE/MWCNTs-Nf/GNPs with increasing deposition time. However, when the deposition time was beyond 200 s, the SW stripping signal does not change significantly, indicating that the accumulation of MA has almost been completed and the amount of MA on the electrode surface achieves saturation. In the light of these experiences a deposition time of 200 s was selected.
Figure 7
3.4.2. Calibration data
15
Page 15 of 42
Under the experimental conditions selected on the optimization studies (–200 mV for 200 s), SWASV
experiments
in
solutions containing different MA concentrations,
at the
SPE/MWCNTs-Nf/GNPs were performed and the results are shown in Fig. 8. As can be seen in
ip t
the insets, the plot of stripping current versus MA concentration is linear over the wide concentration range from 0.02 to 0.1 µM by Ip = 13.49x + 0.1036, R2 = 0.9916 and from 3.0 to
cr
50 µM by Ip = 0.1202x + 2.8132, R2 = 0.998. Detection limit of 6 nM was obtained at signal to
an
Figure 8
us
noise ratio of 3.
M
3.4.3. Selectivity
Under optimum experimental condition, the influence of various foreign species on the
ed
determination of MA was investigated. The tolerance limit was taken as the maximum concentration of the foreign agents, which caused an approximately ±5% relative error in the
pt
determination of analyte. The influence of various foreign species on the determination of 5.0
Ac ce
M MA was investigated. Table 1 shows the obtained results for possible interferences. Table 1
3.5. Impedimetric detection
Impedimetric measurements become popular among the affinity sensors and biosensors. EIS uses a small-amplitude perturbation signal, which makes it an excellent tool for indicating a change in the electric properties of the receptor layer and obtaining the information about the ion transport mechanism and reaction characteristic of electrode interface [51-54].
16
Page 16 of 42
In order to design an impedimetric sensor, it is necessary to set an appropriate relationship between electrical responses of the electrode surface and electrolyte in the absence and presence of the species of interest [55]. In this work, the relationship between charge transfer resistance,
Rct = RT/n2F2Akct[S]
ip t
Rct and bulk concentration of MA can be obtained by the following equation [51-54]. (4)
cr
where, kct is the potential dependent charge transfer rate constant, [S] is the concentration of the
us
redox species (here MA) and the other symbols have their usual meanings.
The EIS behavior of SPE/MWCNTs-Nf/GNPs modified electrode, as MA sensor, was
an
investigated. It can be safely considered that MA oxidation reaction is fast, so that the extent of surface MA is controlled by the bulk MA concentration. Thus, in Eq. (4) one may replace [S]
(5)
pt
1/Rct = k [MA]
ed
the form of Eq. (5) is simply obtained as:
M
with k1[MA], where k1 is a constant. If all other parameters are constant, a linear relationship in
Ac ce
where k includes all constants of Eq. (4). According to this equation, the value of the charge transfer resistance is expected to decrease with increasing MA concentration. The sensitivity of 1/Rct as a function of MA concentration depends on the magnitude of the applied DC potential. Thus, the offset potential was set at 280 mV versus Ag electrode to ensure the MA oxidation being in the kinetic regime. Fig. 9A shows the Nyquist plots obtained on the SPE/MWCNTsNf/GNPs modified electrode in 0.01 M NaOH solutions containing different MA concentrations at 280 mV. The EIS results could be modeled by the Randles’ equivalent circuit. In order to obtain a satisfactory fitting of Nyquist diagrams, it was necessary to replace the double layer
17
Page 17 of 42
capacitance with a constant phase element in the equivalent circuit. The equivalent circuit R1(R2CPE1), consisting of a constant phase element in parallel with a resistance, was found to give the best fit to the experimental data. In this equivalent circuit, R1 corresponds to the
ip t
resistance of the solution, R2 is the charge transfer resistance between the MA and the immobilized GNPs on the electrode surface and the constant phase element corresponds to the
cr
double layer capacitance. The charge-transfer resistance of the electrode reaction is the only
us
circuit element that has a simple physical meaning describing how fast the rate of charge transfer during electrocatalytic oxidation changes with the electrode potential or bulk concentration of
M
Figure 9
an
drug in solution [56].
3.5.1. Calibration data
ed
In evaluating the analytical performance of the electrodes in the quantitative determination of MA, it was necessary to characterize the electrodes with respect to calibration, sensitivity and
pt
detection limits. Calibration was performed by EIS, using solutions containing different MA
Ac ce
concentrations and the results are exhibited Fig. 9B. The calibration plot over the concentration range of 1.15 – 26.9 nM is linear and has a correlation coefficient of 0.9996. The limit of detection for MA was 0.3 nM based on a signal-to-noise ratio equal to 3 (S/N = 3). As there is no data or plot of calibration for MA by any modified electrode, we have compared the results of this modified electrode with some other methods used for MA detection and the results are listed in Table 2. In brief, the novel SPE/MWCNTs-Nf/GNPs for the sensing of MA exhibits high performance.
Table 2 18
Page 18 of 42
3.6. Stability of modified electrode
ip t
The stability of the MWCNTs-Nf/GNPs film modified SPE was tested by means of a repetitive measurement CV response. Only 5% decrease was observed in the current response of 5.0 mM
cr
MA over 10 days testing. The result suggested that the modified electrode has a good stability
us
[1].
an
3.7. The reproducibility of the electrode
To characterize the reproducibility of the electrode, five parallel-made sensors were used to
M
detect 0.1 mM MA by SWASV. The results of five SPE/MWCNTs-Nf/GNPs prepared independently under the same conditions showed a relative standard deviation (RSD%) of 5.1%,
ed
showing the good reproducibility of the electrochemical MA sensor. Moreover, a series of 10
pt
measurements of samples containing 0.1 mM of MA were carried out obtaining a RSD% value
Ac ce
of 4.2.
4. Conclusion
In this work, we have demonstrated a sensitive electrochemical sensor for the detection of MA by MWCNTs-Nf/GNPs modified SPE in alkaline media. The electrode showed electrocatalytic oxidation for MA. The synergistic effect of MWCNTs and gold nanoparticles could greatly improve the electrode performance in 0.01 M NaOH electrolyte. The cyclic voltammetric response of the proposed electrode is about 34 and 2.9 fold that of the bare SPE and MWCNTsNf/SPE, respectively. The sensor has been used for quantitative detection of MA with the 19
Page 19 of 42
SWASV and EIS owning high sensitivity. A wide linear dynamic range, good reproducibility, high stability and fast response were obtained for the determination of MA concentration. Moreover, simple preparation and low cost are some advantages of this disposable modified
ip t
electrode. From the resulting data the information on electron-transfer coefficient, rate constant of electron transfer and reversibility of the current response can be extracted. The results of the
cr
present work indicated that the proposed sensor was suitable for the detection of MA
us
concentration.
an
Acknowledgments
Financial support from the Research Affairs of Shahid Beheshti University is gratefully
ed pt
References
M
appreciated.
Ac ce
[1] C. Yi, Y. Tao, B. Wang, X. Chen, Anal. Chim. Acta 541 (2005) 75-83. [2] N. Kuroda, R. Nomura, O. Al-Dirbashi, S. Akiyama, K. Nakashima, J. Chromatogr. A 798 (1998) 325-334.
[3] M. Nishida, M. Yashiki, A. Namera, K. Kimura, J. Chromatogr. B 842 (2006) 106-110. [4] H. Kalant, Canadian Medical Association 165 (2001) 917-928. [5] C. He, C. Deng, L. Shi, Y. Fu, H. Cao, J. Cheng, Synth. Met. 161 (2011) 293-297. [6] Y. He, A. Vargas, Y.J. Kang, Anal. Chim. Acta 589 (2007) 225-230. 20
Page 20 of 42
[7] D. Djozan, M.A. Farajzadeh, S.M. Sorouraddin, T. Baheri, J. Chromatogr. A 1248 (2012) 2431.
ip t
[8] M. Yonamine, N. Tawil, R.L.M. Moreau, O.A. Silva, J. Chromatogr. B 789 (2003) 73-78. [9] H.P. Hendrickson, A. Milesi-Hallé, E.M. Laurenzana, S.M. Owens, J. Chromatogr. B 806
cr
(2004) 81-87.
us
[10] H. Dai, Y. Wang, X. Wu, L. Zhang, G. Chen, Biosens. Bioelectron. 24 (2009) 1230-1234.
an
[11] K. Yagiuda, A. Hemmi, S. Ito, Y. Asano, Biosens. Bioelectron. 11 (1996) 703-707. [12] A. Miki, T. Keller, P. Regenscheit, R. Dirnhofer, M. Tatsuno, M. Katagi, M. ishikawa, H.
M
Tsuchihashi, J. Chromatogr. B 692 (1997) 319-328.
B 749 (2000) 111-118.
ed
[13] Chinaka, S., Tanaka, S., Takayama, N., Komai, K., Ohshima, T., Ueda, K., J. Chromatogr.
pt
[14] E.M.P.J. Garrido, J.M.P.J. Garrido, N. Milhazes, F. Borges, A.M. Oliveira-Brett,
Ac ce
Bioelectrochemistry 79 (2010) 77-83.
[15] H. Yin, X. Meng, H. Su, M. Xu, S. Ai, Food Chem. 134 (2012) 1225-1230. [16] R.M. Penner, C.R. Martin, Anal. Chem. 59 (1987) 2625-2630. [17] A.R. Fakhari, B. Rafiee, H. Ahmar, A. Bagheri, Anal. Methods 4 (2012) 3314-3319. [18] S. Iijima, Nature 354 (1991) 56-58. [19] Y. Guo, S. Guo, Y. Fang, S. Dong, Electrochim. Acta 55 (2010) 3927-3931. [20] M. Pumera, Chem.—Eur. J. 15 (2009) 4970-4978. 21
Page 21 of 42
[21] N.X. Viet, Y. Ukita, M. Chikae, Y. Ohno, K. Maehashi, K. Matsumoto, P.H. Viet, B. Wang, J. Zhang, G. Cheng, S. Dong, Anal. Chim. Acta 407 (2000) 111-118.
ip t
[22] A.A. Ensafi, , A.R. Allafchian, M. Saraji, B. Farajmand, Talanta 99 (2012) 335-341.
cr
[23] M. Wojciechowski, J. Balcerzak, Anal. Chim. Acta 249 (1991) 433-445. [24] S.A. Borman, Anal. Chem. 54 (1982) 698A-705A.
us
[25] T.M. Florence, Analyst 111 (1986) 489-505.
an
[26] C. Berggren, P. Stalhandske, J. Brundell, G. Johansson, Electroanalysis 11 (1999) 156-160.
M
[27] T.K. Rout, Corrosion Science 49 (2007) 794-817.
[28] K.M. Millan, A. Saraullo, S.R. Mikkelsen, Anal. Chem. 66 (1994) 2943-2948.
ed
[29] A.G.E. Saum, R.H. Cumming, F.J. Rowell, Biosens. Bioelectron. 13 (1998) 511-518.
pt
[30] A. Nogueira, X.R. Novoa, C. Perez, Prog. Org. Coat. 59 (2007) 186-191.
Ac ce
[31] S.K. Roy, M.E. Orazem, J. Power Sources 184 (2008) 212-219. [32] J.S. Daniels, N. Pourmand, Electroanalysis 19 (2007) 1239-1257. [33] P. Sistat, A. Kozmai, N. Pismenskaya, C. Larchet, G. Pourcelly, V. Nikonenko, Electrochim. Acta 53 (2008) 6380-6390. [34] M. Bart, E.C.A. Stigter, H.R. Stapert, G.J. De Jong, W.P. van Bennekom, Biosens. Bioelectron. 21 (2005) 49-59. [35] A. Bonanni, A.H. Loo, M. Pumera, Trends Anal. Chem. 37 (2012) 12-21. 22
Page 22 of 42
[36] B. Rafiee, A.R. Fakhari, Biosens. Bioelectron. 46 (2013) 130-135. [37] K.C. Honeychurch, J.P. Hart, Trends Anal. Chem. 22 (2003) 456-469.
ip t
[38] O.D. Renedo, M.J.A. Martinez, Analy. Chim. Acta 589 (2007) 255-260.
cr
[39] P.V. Dudin, P.R. Unwin, J.V. Macpherson, J. Phys. Chem. C 114 (2010) 13241-13248.
[40] Yu.I. Golovin, D.Yu. Golovin, A.V. Shuklinov, R.A. Stolyarov, V.M. Vasyukov, Tech.
us
Phys. Lett. 37 (2011) 253-255.
an
[41] X. Chen, j. Zhu, Q. Xi, W. Yang, Sens. Actuators B 161 (2012) 648-654.
M
[42] M. Masui, H. Sayo, Y. Tsuda, Journal of Chemical Society B 9 (1968) 973-976. [43] A. Adenier, , M.M. Chehimi, I. Gallardo, J. Pinson, N. Vila, Langmuir 20 (2004) 8243-
ed
8253.
(1993) 1379-1384.
pt
[44] J.A. Squella, B.K. Cassels, M. Arata, M.P. Bavestrello, L.J. Nunez-Vergara, Talanta 40
Ac ce
[45] G. Martinez-Paredes, M.B. Gonzalez-Garcia, A. Costa-Garcia, Electrochim. Acta 54 (2009) 4801-4808.
[46] T. Hezard, K. Fajerwerg, D. Evrard, V. Colliere, P. Behra, P. Gros, Electrochim. Acta 73 (2012) 15-22.
[47] D. Yue, Y. Jia, Y. Yao, J. Sun, Y. Jing, Electrochim. Acta 65 (2012) 30-36. [48] E. Laviron, J. Electroanal. Chem. 101 (1979) 19-28. [49] L. Xiao, G.G. Wildgoose, R.G. Compton, Anal. Chim. acta 620 (2008) 44-49. 23
Page 23 of 42
[50] Q. Zhao, Y. Chai, R. Yuan, J. Luo, Sens. Actuators B 178 (2013) 379-384. [51] M.D. Levi, D. Aurbach, J. Electrochem. Soc. 149 (2000) E215.
ip t
[52] M. Shamsipur, S.H. Kazemi, M.F. Mousavi, Biosens. Bioelectron. 24 (2008) 104-110. [53] C.C.M. Martinez, E.F. Treo, R.E. Madrid, C.C. Felice, Biosens. Bioelectron. 26 (2010)
cr
1239-1244.
us
[54] M. Shamsipur, M. Asgari, M.F. Mousavi, R. Davarkhah, Electroanalysis 24 (2012) 357-367.
an
[55] D. Bethell, M. Brust, D.J. Schiffrin, C. Kiely, J. Electroanal. Chem. 409 (1996) 137-143.
Anal. Biochem. 373 (2008) 337-348.
M
[56] M. Hajjizadeh, A. Jabbari, H. Heli, A.A. Moosavi-Movahedi, A. Shafiee, K. Karimian,
ed
[57] C.C. Chou, M.R. Lee, Analy. Chim. Acta 538 (2005) 49–56. [58] Y. He, Y.J. Kang, J. Chromatogr. A 1133 (2006) 35–40.
pt
[59] O. Al-Dirbashi, N. Kuroda, S. Akiyama, K. Nakashima, J. Chromatogr. B 695 (1997) 251–
Ac ce
258.
[60] I. Koide, O. Noguchi, K. Okada, A. Yokoyama, H. Oda , S. Yamamoto, H. Kataoka, J. Chromatogr. B 707 (1998) 99–104. [61] G. Sakai, S. Nakata, T. Uda, N. Miura, N. Yamazoe, Electrochim. Acta 44 (1999) 3849– 3854.
Figure captions 24
Page 24 of 42
Fig. 1. (A) SEM images of the SPE surface modified with MWCNTs-Nf and (B) MWCNTs-
ip t
Nf/GNPs; (C) EDX spectrum of SPE/MWCNTs-Nf/GNPs surface.
Fig. 2. SEM photo and EDX mapping of SPE/MWCNTs-Nf/GNPs surface. SEM photo (a), EDX (b) and EDX mapping of gold
(c).
us
cr
mapping of carbon
Fig. 3. Cyclic voltammograms for bare SPE (a), SPE/MWCNTs-Nf (b) and SPE/MWCNTs-
M
an
Nf/GNPs (c) in 0.01 M NaOH solution containing 0.01 M MA, scan rate: 100 mVs–1.
Fig. 4. (A) Cyclic voltammograms of SPE/MWCNTs-Nf/GNPs in 0.01 M NaOH containing 5.0
ed
mM MA at different scan rates (1, 5, 10, 25, 50, 100, 125, 150 and 200 mV s–1); (B) Variation of peak current versus scan rate; (C) Dependence of the peak potential, Ep, to the logν; (D) Tafel
Ac ce
pt
Plot for modified electrode, scan rate: 1 mV s–1.
Fig. 5. SW voltammograms at the bare SPE (a), SPE/MWCNTs-Nf (b), SPE/MWCNTsNf/GNPs (c) and SPE/MWCNTs-Nf/GNPs after using –200 mV for 200 s as stripping step (d) in 0.01 M NaOH solution containing 0.1 mM MA.
25
Page 25 of 42
Fig. 6. (A) Anodic stripping determination of 0.1 mM MA in 0.01 M NaOH solution at SPE/MWCNTs-Nf/GNPs using different electrodeposition potentials (+100, 0, −100, −200,
ip t
−300, −400 mV), tdep = 200 s; (B) Chart spot of voltammograms showed in (A).
cr
Fig. 7. (A) Anodic stripping determination of 0.1 mM MA in 0.01 M NaOH solution at
an
mV; (B) Chart spot of voltammograms showed in (A).
us
SPE/MWCNTs-Nf/GNPs using different electrodeposition times from 0 to 350 s, Edep = –200
Fig. 8. Calibration curve for different MA concentration (0.02, 0.05, 0.07, 0.09, 0.1, 3, 5, 9, 15,
M
25, 35 and 50 µM) measured by SWASV after using –200 mV for 200 s in 0.01 M NaOH
ed
solution at SPE/MWCNTs-Nf/GNPs; Deposition potential: –200 mV; deposition time: 200 s; pulse amplitude: 10 mV; and pulse width: 10 ms. The insets show the relationship between Ip
Ac ce
pt
and different concentrations of MA.
Fig. 9. (A) Nyquist plots obtained at SPE/MWCNTs-Nf/GNPs for different concentration of MA in 0.01 M NaOH solution in the absence (a) and in the presence of 1.15 (b), 4.1 (c), 8.3 (d), 11.6 (e), 14.7 (f), 19 nM (g) MA. Conditions: EDC = 280 mV, frequency range of 100000 to 0.01 Hz. Symbols are the experimental data and lines show the approximated results. (B) Calibration graph of 1/Rct as a function of MA concentration.
26
Page 26 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Table 1 The effect of various foreign species on the determination of 5.0 M MA. Foreign species Tolerance limit Recovery% Uric acid 1000 99.8 ± 1.5 L-tryptophan 100 101.2 ± 3.5 Acetaminophen 100 98.8 ± 1.5 Ascorbic Acid 50 97.4 ± 1.1 Epinephrine 5 98.2 ± 3.5 Isoprenaline 1 97.3 ± 3.2
28
Page 27 of 42
ip t cr us an M ed
Table 2 Analytical parameters for detection of MA by different methods Sample
Conductivity-based immunosensor
LOD
RSD (%)
Ref.
Human urine
1–10 mg/L
0.5 mg/L
5
[11]
Serum
0.5– 200µg/L
0.04 µg/L
< 8.0
[57]
ECLg/Ru(bpy)32+
–
0.13–180 mg/L
37 µg/L
1.1
[1]
ECL/Ru(bpy)32+
Human urine
0.015– 14.8 mg/L
1.48 µg/L
3.1
[10]
Human urine
1.0–1500µg/L
0.3 µg/L
< 5.0
[6]
Human urine
10–1500 µg/L
2 µg/L
5.1
[7]
b
Ac ce
SPME–LC/ESI–MS/MS
a
LDR
pt
Method
HS–LPME /HPLC–UV
a
MISPE–DLLME–GC–FID LC/MS/MS
Rat serum
0.3–1000 µg/L
0.3 µg/L
< 5.0
[9]
LLLME c/HPLC–UV
Human urine
1.0–1500 µg/L
0.5 µg/L
< 5.0
[58]
CE–UV
Human urine
0.2–500 mg/L
0.1 mg/L
1.4
[13]
Hair
0.5–120 µg/g hair
0.5 mg/L
5.2
[12]
HPLC/Fluorescence
Human urine
4.6–1800 µg/L
1 µg/L
2.6
[59]
HS–SPME/GC–NPDf
Hair
4–160 µg/g hair
0.4 µg/g hair
< 10
[60]
Hair
250–0.63 µg /g hair
0.25 µg/g hair
–
[3]
Saliva
5–100 µg/L
0.5 µg/L
–
[8]
Human urine
0.1–1000 µg/L
100 µg/L
–
[61]
–
0.21– 0.5 µg/L
56 ng/L
–
This work
e
IMS
SPME/GC–MS
h
SPME/GC–MS i
SPR -based immunosensor SPE/MWCNTs-
EIS
Nf/GNPs j
29
Page 28 of 42
Nf/GNPs j
3.7–18 µg/L and
SWASV
1.1 µg/L
4.2
0.55–9.2 mg/L a
Solid-phase microextraction/Liquid chromatography/Electrospray ionization/Tandem mass spectrometry Headspace liquid-phase microextraction c Single drop liquid–liquid–liquid microextraction d Capillary electrophoresis e Ion mobility spectrometry f Nitrogen–phosphorus detector g Electrochemiluminescence
i
Surface-plasmon-resonance
j
Gold nanoparticles-Multiwalled carbon nanotubes-Nafion modified Screen-printed carbon electrode
cr
With one-pot derivatization
Ac ce
pt
ed
M
an
us
h
ip t
b
Scheme 1
30
Page 29 of 42
ip t cr us an M ed pt Ac ce Fig. 1
31
Page 30 of 42
B
1 µm
C
Ac ce
pt
ed
M
an
us
cr
1 µm
ip t
A
Fig. 2 32
Page 31 of 42
c
Ac ce
pt
ed
M
an
us
cr
ip t
a
Fig. 3 33
Page 32 of 42
cr
ip t
c
a
Ac ce
pt
ed
M
an
us
b
Fig. 4
34
Page 33 of 42
35
Page 34 of 42
ed
pt
Ac ce us
an
M
cr
ip t
ed
pt
Ac ce us
an
M
cr
ip t
C
36
Page 35 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Fig. 5
37
Page 36 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Fig. 6
38
Page 37 of 42
Fig. 7
Ac ce
pt
B
ed
M
an
us
cr
ip t
A
39
Page 38 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Fig. 8
40
Page 39 of 42
Fig. 9
ed
M
an
us
cr
ip t
A
Ac ce
pt
B
41
Page 40 of 42
Authers Biography Ali Reza Fakhari received his B.S. degree at Tarbiat Moalem University in 1988, M.S. degree at Shiraz University in 1991 and Ph.D. in Analytical Chemistry at Tarbiat Modarres University,
ip t
Tehran, Iran in 1997. His Ph.D. supervisor was Professor Mojtaba Shamsipur. He has got associate professor since 2003 and professorship since 2008. He has been supervisor of 38 M.S.
cr
and 6 Ph.D. students. His current research activities include chemical and biochemical sensors,
us
electro-organic synthesis, capillary electrophoresis and other separation methods.
an
Banafsheh Rafiee received her B.S. degree in Applied Chemistry in 2005, M.S. degree in Analytical Chemistry at K.N. Toosi University of Technology in 2008 and Ph.D. degree in
M
Department of Chemistry at Shahid Beheshti University (Tehran, Iran) in 2013. Her research
different applications.
ed
interest mainly focuses on the use of nanomaterials based sensors (chemical and biochemical) for
pt
Mohammad Ghaffarzadeh obtained his B.S. in pure chemistry in 1993 from Tabriz University.
Ac ce
He completed his M.S. in Organic Chemistry in Sharif University of Technology in 1996. After completing his Ph.D. in the same university in 2001, he joined the Chemistry and Chemical Engineering Research Center of Iran (CCERCI), Tehran, as an assistant professor. His research interests focus on organic syntheses methodology, new drug design & synthesis and scale-up of organic reactions.
42
Page 41 of 42
Ac
ce
pt
ed
M
an
us
cr
i
Graphical Abstract (for review)
Page 42 of 42
S0925-4005(15)00410-4 http://dx.doi.org/doi:10.1016/j.snb.2015.03.077 SNB 18271
To appear in:
Sensors and Actuators B
Received date: Revised date: Accepted date:
30-12-2014 26-3-2015 30-3-2015
Please cite this article as: B. Rafiee, A.R. Fakhari, M. Ghaffarzadeh, Impedimetric and Stripping Voltammetric Determination of Methamphetamine at Gold NanoparticlesMultiwalled Carbon Nanotubes Modified Screen Printed Electrode, Sensors and Actuators B: Chemical (2015), http://dx.doi.org/10.1016/j.snb.2015.03.077 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Highlights 1. SPE/MWCNTs-Nf/GNPs was used as a novel electrochemical sensor for quantitative detection of MA in alkaline solutions. 2. The MA oxidation has been investigated by SWASV and EIS owning high sensitivity.
ip t
3. The synergistic effect of MWCNTs and GNPs could greatly improve the electrode performance.
Ac ce
pt
ed
M
an
us
cr
4. Wide linear dynamic range, good reproducibility, high stability and fast response were the main advantages of the proposed impedimetric sensor.
1
Page 1 of 42
Impedimetric and Stripping Voltammetric Determination of Methamphetamine at Gold Nanoparticles-Multiwalled Carbon
*
cr
Banafsheh Rafiee and Ali Reza Fakhari
ip t
Nanotubes Modified Screen Printed Electrode
Department of Chemistry, Faculty of Sciences, Shahid Beheshti University, G. C., PO Box 19396-4716,
Ac ce
pt
ed
M
an
us
Tehran, Iran
*
Corresponding author, Tel.: +98 21 22431661; fax: +98 21 22431683. E-mail address: [email protected] (A.R. Fakhari).
2
Page 2 of 42
Abstract
ip t
A high performance electrochemical sensor for the detection of methamphetamine (MA) at the gold nanoparticle (GNP)/multiwalled carbon nanotube (MWCNT)-Nafion (Nf) modified screen
cr
printed electrode (SPE) is reported. Gold nanoparticles were electrodeposited on the substrate using a constant potential. Energy dispersive X-ray (EDX) spectrum and mapping and also
us
scanning electron microscopy (SEM) results showed that GNPs were deposited and dispersed
an
uniformly on the SPE/MWCNTs-Nf-Nf, respectively. The electrochemical behavior of MA was studied by cyclic voltammetry (CV), and modified electrode was used for the determination of
M
sub-nanomolar amounts of MA in samples using square wave stripping voltammetry (SWSV) and electrochemical impedance spectroscopy (EIS). Under the optimized experimental
ed
conditions, the modified SPE revealed broad linear ranges of 0.02–0.1 and 3.0–50 µM (LOD = 6 nM) for SWSV and 1.15–26.9 nM (LOD = 0.3 nM) for EIS. Finally, the SPE/MWCNTs-
pt
Nf/GNPs showed stable electrochemical cyclic voltammetry responses. The high performances of the novel MA impedimetric sensor are mainly attributed to high surface area-to-volume ratio,
Ac ce
excellent conducting capability and interface-dominated properties of GNPs which in combination with special properties of MWCNTs provide an effective modifier for MA oxidation. Moreover, using sensitive methods like impedimetric and stripping results in excellent responses.
Keywords: Methamphetamine; Impedimetric sensor; Anodic stripping voltammetry; Gold Nanoparticles; Screen Printed Electrode; MWCNTs 3
Page 3 of 42
1. Introduction Methamphetamine (MA) (Scheme 1) is a powerful central nervous system stimulant [1] that
ip t
brings about wakefulness and anorexia [2] and is abused in many countries [3]. It produces a rapid pleasurable feeling, which is followed by feelings of depression and irritability when the
us
cr
drug wears off.
an
Scheme 1. Structural formula of methamphetamine.
The drug is available as water soluble white crystalline form. Pure methamphetamine, the
M
smokable form of the drug, is called “glass”, “ice”, “crystal” or “quartz” because of its clear, chunky crystals which resemble frozen water. Despite warnings of irreversible damage to the
ed
central nervous system due to its consumption (even strokes and death), enhancement the abuse
pt
of this drug (especially among the young generation) is causing an increase in cost and crime and finally serious social problems in many countries [4, 5]. One reason might be the ease of
Ac ce
synthesis from readily available raw materials, which brings lots of money for sellers and smugglers [6]. Therefore, there is a great interest for the quantitative analysis of such drugs by an inexpensive and powerful method in forensic as well as clinical laboratories. Several methods have been introduced for this purpose like gas chromatography (GC) [7], GC–mass spectrometry (GC–MS) [8], high-performance liquid chromatography (HPLC) [6], HPLC–tandem mass spectrometry (LC/MS/MS) [9], electrochemiluminescence (ECL) [10], immunoassay [11], Ion mobility spectrometry (IMS) [12] and capillary electrophoresis (CE) [13]. Although these methods are accurate but they suffer from problems of time-consuming, laborious operations and 4
Page 4 of 42
expensive apparatuses. Furthermore, they need several preparation steps before main procedure. Therefore, a simple, fast and accurate method is necessary for routine analysis and detecting MA in samples. Electrochemical detection is a simple and inexpensive method and also is attractive
ip t
as it can provide sensitivity and reduces analysis time to enable continuous real-time measurements compared to the above methodologies. To our knowledge, electrochemical
cr
method has scarcely been applied to determine MA. Our findings show that there is just one
us
report for electrochemical study of MA which the authors have investigated the electrochemical behavior of MA at a glassy carbon electrode [14].
an
In electrochemical analysis, the key component is electrode modification, which requires the selection of suitable material to improve the determination performance [15]. In principle, the
M
electroanalytical detection limit at a nanoelectrode can be much lower than that at an analogous macrosized electrode because the ratio between the faradic and capacitive currents is higher [16].
ed
Carbon nanotubes (CNTs) have attracted much attention due to their special properties [17-19].
pt
As electrode modifiers, CNTs show negligible surface fouling [20], decreased overpotential and increased voltammetric currents. Indeed, CNT electrode is driving the electron transfer reaction
Ac ce
faster than many other carbon electrodes surfaces observed, with very small apparent activation barrier at the electrode surface [21]. Nanosized particles of noble metals, especially gold nanoparticles (GNPs), have received great interests due to their high surface area-to-volume ratio, excellent conducting capability, excellent biocompatibility and their interface-dominated properties. Anodic stripping voltammetry (ASV) has been recognized as a powerful technique for electrochemical measurements of trace analytes in which a preconcentration step is combined with a stripping step, thereby enhancing the sensitivity [22]. When square-wave voltammetry 5
Page 5 of 42
(SWV) is employed for anodic stripping, the resulting method of square wave anodic stripping voltammetry (SWASV) offers many advantages over the more popular methods like differentialpulse ASV (DPASV) [23-25].
ip t
Electrochemical impedance spectroscopy (EIS) is a rapidly developing technique for the study of sensing events at the surface of an electrode [26] and is widely used in different fields’ studies
cr
[27-33]. Faradic impedimetric systems are based on measuring the charge transfer resistance of a
us
redox probe at an electrode interface. Impedance detection has been found to be sensitive, rapid and can detect at very low concentration reaching a limit of detection of 10−18 M in some cases
an
[34]. Moreover, the measurement does not have any specific prerequisites (e.g., labels or electroactive moieties in the molecule) [35]. carbon
electrodes
(SPEs)
represent
a
widely
accessible,
disposable
M
Screen-printed
electrochemical sensor, simple, inexpensive and non-toxic [36]. Replacement of conventional
ed
electrochemical cells by SPEs connected to miniaturized potentiostats is a main trend in the shift of lab electrochemical equipments to hand-held field analyzers [37]. They are also suitable for
pt
working with microvolumes and for decentralized assays (point of care tests), etc.
Ac ce
The main goal of this work is to investigate the electrochemical response of MA on the surface of SPE/MWCNTs-Nf-Nf/GNPs and develop a novel electrochemical sensor for quantitative detection of MA in forensic or clinical samples. For this purpose, MA was determined by SWASV. We have also reported the impedimetric detection to have comprehensive investigation of MA oxidation at this modified electrode. To the best of the author’s knowledge, this study presents the first ever electrochemical detection of MA with this type of nano-modified electrodes.
6
Page 6 of 42
2. Experimental 2.1. Chemicals and materials
ip t
Multiwalled carbon nanotubes with purity 95% (20‒40 nm diameter and 1‒10 µm length) were obtained from Research Institute of Petroleum Industry (Tehran, Iran). MA, as the hydrochloride
cr
salt, was purchased from Dr Ghaffarzadeh (Institute of Chemistry and Chemical Engineering).
us
Nafion 5% solution was purchased from Sigma. All other solvents and reagents were purchased from Aldrich or Merck and were used without further purification. A stock solution of MA (0.10
an
M) was prepared by dissolving MA in deionized water. MA solutions were prepared by diluting aliquots of the MA stock solutions with a carrier solution and were freshly prepared just prior to
M
use. All other solutions were prepared with doubly distilled water. All experiments were carried
pt
2.2. Instruments
ed
out at room temperature.
Ac ce
All electrochemical experiments were performed using Autolab potentiostat/galvanostat type 30 (2) (Eco Chemie, Netherlands), equipped with FRA and GPES 4.9 software. Screen-printed carbon electrode (SPE) (3.0 mm in diameter) from Dropsens (Spain) was used as a planar three electrode based on a graphite working electrode, a carbon counter electrode and a silver pseudoreference electrode. The electrode was rinsed in deionized water and preconditioned in 0.10 M HCl solution by potential scanning in –0.3 to +1.3 V at a scan rate of 100 mV s-1. The following parameters were employed for CV and SWASV, respectively: CV: scan rate 50 mV s-1 and MA solution of 5.0 mM; SWASV: pulse amplitude 10 mV, pulse width 10 ms and MA solution of 7
Page 7 of 42
0.1 mM. EIS experiments carried out with a dc-offset potential of 280 mV and in the frequency range of 100000 to 0.01 Hz. Scanning electron microscopy (SEM) images, were obtained using KYKY-EM3200 SEM and energy dispersive X-ray (EDX) spectrum and EDX mapping were
ip t
obtained using Philips XL-30 ESEM.
cr
2.3. Preparation of modified electrode
us
MWCNTs were stirred in concentrated HNO3 for 6h and then refluxed in the mixture of concentrated H2SO4:HNO3 (3:1) for 24 h to obtain the carboxylated multi-walled carbon
an
nanotubes [36]. The MWCNTs were washed with doubly distilled water and dried in vacuum at 80 ºC. Carboxylated MWCNTs (10.0 mg) and 5.0 µl of 5% nafion solution were dispersed in 5.0
M
ml water with ultrasonication for 1 h to get a homogenous suspension. The SPE/MWCNTs-Nf was prepared by casting 10.0 µl of the suspension onto the surface of screen printed electrode
ed
and let to evaporate to dryness at room temperature. The electrodeposition of gold nanoparticles on SPE/MWCNTs-Nf was conducted using a constant potential. The characteristic of gold
pt
deposition on the electrode surface is strongly influenced by several parameters: the two most
Ac ce
important being the HAuClO4 concentration and the deposition time [38]. Both factors have been optimized and the constant potential of −400 mV versus Ag was applied on these electrodes for a period of 30 seconds in 0.10 M HCl solution containing 10.0 mM HAuCl4 [39].
3. Results and discussion 3.1. Structures characterization
8
Page 8 of 42
The surface morphology and nanostructure of the screen printed electrode/carboxylated multiwalled carbon nanotube/gold nanoparticles (SPE/MWCNTs-Nf/GNPs) was characterized
ip t
by SEM and EDX techniques.
cr
3.1.1. SEM results
us
Fig. 1 shows the SEM images of the SPE surface modified with MWCNTs-Nf (A) and MWCNTs-Nf/GNPs (B). As shown in this figure, a network-like structure of MWCNTs without
an
aggregation was observed on the SPE surface which suggested that the MWCNTs were immobilized on the SPE surface. The diameter of the MWCNTs was about 14 – 40 nm. This
M
figure also shows gold nanoparticles electrodeposited onto the SPE/MWCNTs-Nf. White spots in the SEM images present gold nanoparticles which are distributed uniform and dense on the
ed
SPE/MWCNTs-Nf. The particle dimensions are in the range of 17 – 40 nm. A volume array of MWCNTs ensures a uniform spatial distribution and storage of gold nanoparticles, while
pt
remaining highly permeable for a flow of liquid or gas (not presenting large hydrodynamic
Ac ce
resistance in contrast to compacted powders) [40], providing an increased sensing area and effective mass transportation pathway [41].
3.1.2. EDX spectrum
Fig. 1C shows the EDX spectrum of the composites. The element of C in the EDX spectrum is basically from the MWCNTs-Nf. The presence of gold signals in the spectrum suggested the
9
Page 9 of 42
nanocomposite contained gold particles. Consequently, the presence of gold nanoparticles on the SPE/MWCNTs-Nf which was shown by SEM images was confirmed by EDX technique.
ip t
Figure 1 3.1.3. EDX mapping
cr
EDX mapping provides, in addition to the conventional SEM image, a meaningful picture of the
us
element distribution of a surface. Fig. 2 shows the SEM image and EDX mapping of SPE/MWCNTs-Nf/GNPs surface. The color represents the type of element, and the darkness
an
reflects the element's concentration. As shown in this figure, the distribution of carbon is quite concentrated, which indicates that the majority of the modified layer was MWCNTs. Moreover,
M
the EDX mapping (c), clearly shows that gold nanoparticles are distributed highly uniform on the
ed
modified electrode surface.
Ac ce
pt
Figure 2
3.2. Cyclic voltammetric response of the MWCNTs/GNPs modified SPE in MA solution As an initial test for the performance of modified electrode in MA oxidation, cyclic voltammograms of three electrodes in 0.01 M NaOH solution containing 0.01 M MA with a scan rate of 100 mV s–1 were compared and the results are exhibited in Fig. 3. The MA oxidation potential peak was seen at about Ep = 0.45 V. The appearance of a peak at this Ep value resulting from the oxidation of aliphatic secondary amines has also been described in the literature for
10
Page 10 of 42
other aliphatic amines [42,43] and as mentioned in previous work, MA is oxidized in aqueous electrolytes through a one electron transfer followed by a chemical reaction (EC mechanism). The chemical reaction is fast enough for the reduction of the cation radical not to occur in the
cr
reverse scan, indicating an irreversible reaction for MA oxidation.
ip t
time scale of voltammetry [44]. The cyclic voltammogram shows no reduction peak in the
us
Figure 3 Furthermore, cyclic voltammograms of SPE/MWCNTs-Nf/GNPs in solutions of different pH
an
values containing 5.0 mM MA in the potential range of 0 – 1200 mV versus Ag and with a scan rate of 50 mVs−1 were taken. Over the entire pH range examined (2 – 12), a single anodic peak
M
was observed. The highest current peak was observed at pH 12, therefore 0.01 M NaOH solution was used in other experiments as electrolyte solution. In spite of most of the electrochemical
ed
studies with gold nano particles which have done in acidic medias [45, 46], for the proposed electrode peak current of MA oxidation in NaOH solution was much higher than in acidic one. It
pt
can be explained by this fact that the MA secondary amine group is more easily oxidized in basic solution than in acidic solution, and this data correlates well with the pKa = 10.1 of the amine
Ac ce
function of MA [14].
3.3. The effect of scan rate on the electrochemical behavior Cyclic voltammograms in Fig. 4A are shown for different scan rates from 1 – 200 mV s−1 in 0.01 M NaOH solution in the presence of 5.0 mM MA. The experiment result shows that the MA oxidation peak current increases linearly with the sweep rates in the range of 1 – 200 mV s-1 (y =
11
Page 11 of 42
1.0667x + 9.1664) and with a correlation coefficient of 0.997 (Fig. 4B). This means that the electrocatalytic reaction of MA is an adsorption-controlled process at the modified electrode. Moreover, the oxidation potential shifts positively from 409 to 482 mV. It is known that for the
ip t
reversible electrode reaction, the oxidation peak potential is independent of scan rate [47]. Therefore existence of oxidation potential shift represents a kinetic limitation in the reaction
us
cr
between the active sites and MA.
an
Figure 4 Plotting the Epa vs. logν produces a straight line with a slope of 0.2796 which is shown in Fig. 4C.
M
According to Laviron’s equation [48], the slop is equal to b/2 and b = 2.303RT/(1 − α) nαF.
ed
Laviron derived general expressions for the linear potential sweep voltammetric response of electroactive species at small concentrations [48]. The expressions for peak-to-peak potential
Ac ce
pt
separations of ΔEp > 200/n mV, where n is the number of exchanged electrons, are as follows:
(1) (2)
where X = RT / (1-αs) nF, Y = RT / αnF, m = (RT/F) (ks/nν), Epa is the anodic peak potential and αs, ks, and ν are the electron-transfer coefficient, apparent charge-transfer rate constant, and potential scan rate, respectively. From these expressions, as can be determined by measuring the
12
Page 12 of 42
variation of the peak potential with respect to the potential scan rate, and ks can be determined for electron transfer between the electrode and the surface-deposited layer by measuring the ΔEp values. According to Fig. 4C, it could be observed that for potential scan rates of 100 to 400 mV
ip t
s-1, Ep and logv present a good linear relationship. The values of Ep are proportional to the logarithm of the potential sweep rate showed by Laviron. Use of the plot and Eqs. (1) and (2),
cr
the value of αs,a (anodic electron-transfer coefficient) was determined to be 0.78. Moreover, the
us
mean value of ks was determined to be 0.44 s-1.
The Tafel plot derived from the rising part of a voltammogram recorded for MA oxidation at a
an
scan rate of 1 mV s–1 and the plot is exhibited in Fig. 4D. The Tafel equation for anodic reactions
log I = log I0 + (1–
nF/2.303 RTE
M
is:
(3)
ed
This plot gives a Tafel slope of 4.64 V. Assuming a “one electron transfer” to be rate limiting step, a value of 0.73 was obtained for the charge transfer coefficient of the catalytic reaction, αn
Ac ce
pt
= 0.73.
3.4. Study of electrochemical behavior of MA at SPE/MWCNTs-Nf/GNPs by SWASV Since CV was not sensitive for the determination of low contents of compounds, SWV studies were performed. The SWASVs were recorded at different modified screen printed electrodes. Fig. 5 shows the results obtained by SWASV at the bare SPE (a), SPE/MWCNTs-Nf (b), SPE/MWCNTs-Nf/GNPs (c) and SPE/MWCNTs-Nf/GNPs after using –200 mV for 200 s as stripping step (d) in 0.01 M NaOH solution containing 0.1 mM MA.
Figure 13 5
Page 13 of 42
ip t
It can be seen that the currents at the bare screen printed carbon electrode and SPE modified with MWCNTs-Nf are negligible. In the presence of gold nanoparticles at the modifier layer, the
cr
oxidation current increases significantly so that a well-defined oxidation peak can be observed at a potential about 280 mV (curve c). The coverage of the GNPs on the carbon nanotubes is such
us
that the nanotubes themselves can simply be considered as a high area support and the
an
electroactivity arises solely from the GNPs [49].
At curve (d) the modifier layer is the same as the modifier layer at curve (c), the only difference
M
is the potential used (–200 mV for 200 s) before MA oxidation as stripping step which accumulate the analyte prior to the oxidation. As can be seen, this electrode exhibited the
ed
sharpest and the highest signal compared to the others for 0.1 mM MA solution. Because the MWCNTs-Nf/GNPs nanocomposites were employed by taking advantage of its specific affinity
pt
of the nitrogen to gold nanoparticles and fast electron transfer rate of MWCNTs, on the other
Ac ce
hand, owing to the special physicochemical properties of nanomaterials, they can obviously improve the sensitivity and selectivity of stripping voltammetry techniques [50]. Therefore, using MWCNTs and gold nanoparticles as modifier layer and –200 mV potential for anodic stripping voltammetry are the best conditions for MA detection at the SPE in the 0.01 M NaOH solution by SWASV.
3.4.1. Optimization of conditions for the SWASV
14
Page 14 of 42
The observed stripping peak of MA at MWCNTs-Nf/GNPs modified SPE is strongly affected by parameters such as Edep, and tdep.
ip t
3.4.1.1. Effect of deposition potential (Edep) The effect of electrodeposition potential was investigated for a fixed period of time, in the
cr
presence of 0.1 mM MA at different applied potentials (+100, 0, −100, −200, −300, −400 mV).
us
Fig. 6 shows the stripping currents. The results indicated that the optimum deposition potential
an
was −200 mV under this condition.
3.4.1.2. Effect of deposition time (tdep)
M
Figure 6
ed
The effect of the deposition time on the peak current of 0.1 mM MA has been also studied in the range from 0 to 350 s and the results are exhibited in Fig. 7. The results indicated that the peak
pt
current increased from 0 up to 200 s. This is because more and more MA accumulated on the
Ac ce
surface of the SPE/MWCNTs-Nf/GNPs with increasing deposition time. However, when the deposition time was beyond 200 s, the SW stripping signal does not change significantly, indicating that the accumulation of MA has almost been completed and the amount of MA on the electrode surface achieves saturation. In the light of these experiences a deposition time of 200 s was selected.
Figure 7
3.4.2. Calibration data
15
Page 15 of 42
Under the experimental conditions selected on the optimization studies (–200 mV for 200 s), SWASV
experiments
in
solutions containing different MA concentrations,
at the
SPE/MWCNTs-Nf/GNPs were performed and the results are shown in Fig. 8. As can be seen in
ip t
the insets, the plot of stripping current versus MA concentration is linear over the wide concentration range from 0.02 to 0.1 µM by Ip = 13.49x + 0.1036, R2 = 0.9916 and from 3.0 to
cr
50 µM by Ip = 0.1202x + 2.8132, R2 = 0.998. Detection limit of 6 nM was obtained at signal to
an
Figure 8
us
noise ratio of 3.
M
3.4.3. Selectivity
Under optimum experimental condition, the influence of various foreign species on the
ed
determination of MA was investigated. The tolerance limit was taken as the maximum concentration of the foreign agents, which caused an approximately ±5% relative error in the
pt
determination of analyte. The influence of various foreign species on the determination of 5.0
Ac ce
M MA was investigated. Table 1 shows the obtained results for possible interferences. Table 1
3.5. Impedimetric detection
Impedimetric measurements become popular among the affinity sensors and biosensors. EIS uses a small-amplitude perturbation signal, which makes it an excellent tool for indicating a change in the electric properties of the receptor layer and obtaining the information about the ion transport mechanism and reaction characteristic of electrode interface [51-54].
16
Page 16 of 42
In order to design an impedimetric sensor, it is necessary to set an appropriate relationship between electrical responses of the electrode surface and electrolyte in the absence and presence of the species of interest [55]. In this work, the relationship between charge transfer resistance,
Rct = RT/n2F2Akct[S]
ip t
Rct and bulk concentration of MA can be obtained by the following equation [51-54]. (4)
cr
where, kct is the potential dependent charge transfer rate constant, [S] is the concentration of the
us
redox species (here MA) and the other symbols have their usual meanings.
The EIS behavior of SPE/MWCNTs-Nf/GNPs modified electrode, as MA sensor, was
an
investigated. It can be safely considered that MA oxidation reaction is fast, so that the extent of surface MA is controlled by the bulk MA concentration. Thus, in Eq. (4) one may replace [S]
(5)
pt
1/Rct = k [MA]
ed
the form of Eq. (5) is simply obtained as:
M
with k1[MA], where k1 is a constant. If all other parameters are constant, a linear relationship in
Ac ce
where k includes all constants of Eq. (4). According to this equation, the value of the charge transfer resistance is expected to decrease with increasing MA concentration. The sensitivity of 1/Rct as a function of MA concentration depends on the magnitude of the applied DC potential. Thus, the offset potential was set at 280 mV versus Ag electrode to ensure the MA oxidation being in the kinetic regime. Fig. 9A shows the Nyquist plots obtained on the SPE/MWCNTsNf/GNPs modified electrode in 0.01 M NaOH solutions containing different MA concentrations at 280 mV. The EIS results could be modeled by the Randles’ equivalent circuit. In order to obtain a satisfactory fitting of Nyquist diagrams, it was necessary to replace the double layer
17
Page 17 of 42
capacitance with a constant phase element in the equivalent circuit. The equivalent circuit R1(R2CPE1), consisting of a constant phase element in parallel with a resistance, was found to give the best fit to the experimental data. In this equivalent circuit, R1 corresponds to the
ip t
resistance of the solution, R2 is the charge transfer resistance between the MA and the immobilized GNPs on the electrode surface and the constant phase element corresponds to the
cr
double layer capacitance. The charge-transfer resistance of the electrode reaction is the only
us
circuit element that has a simple physical meaning describing how fast the rate of charge transfer during electrocatalytic oxidation changes with the electrode potential or bulk concentration of
M
Figure 9
an
drug in solution [56].
3.5.1. Calibration data
ed
In evaluating the analytical performance of the electrodes in the quantitative determination of MA, it was necessary to characterize the electrodes with respect to calibration, sensitivity and
pt
detection limits. Calibration was performed by EIS, using solutions containing different MA
Ac ce
concentrations and the results are exhibited Fig. 9B. The calibration plot over the concentration range of 1.15 – 26.9 nM is linear and has a correlation coefficient of 0.9996. The limit of detection for MA was 0.3 nM based on a signal-to-noise ratio equal to 3 (S/N = 3). As there is no data or plot of calibration for MA by any modified electrode, we have compared the results of this modified electrode with some other methods used for MA detection and the results are listed in Table 2. In brief, the novel SPE/MWCNTs-Nf/GNPs for the sensing of MA exhibits high performance.
Table 2 18
Page 18 of 42
3.6. Stability of modified electrode
ip t
The stability of the MWCNTs-Nf/GNPs film modified SPE was tested by means of a repetitive measurement CV response. Only 5% decrease was observed in the current response of 5.0 mM
cr
MA over 10 days testing. The result suggested that the modified electrode has a good stability
us
[1].
an
3.7. The reproducibility of the electrode
To characterize the reproducibility of the electrode, five parallel-made sensors were used to
M
detect 0.1 mM MA by SWASV. The results of five SPE/MWCNTs-Nf/GNPs prepared independently under the same conditions showed a relative standard deviation (RSD%) of 5.1%,
ed
showing the good reproducibility of the electrochemical MA sensor. Moreover, a series of 10
pt
measurements of samples containing 0.1 mM of MA were carried out obtaining a RSD% value
Ac ce
of 4.2.
4. Conclusion
In this work, we have demonstrated a sensitive electrochemical sensor for the detection of MA by MWCNTs-Nf/GNPs modified SPE in alkaline media. The electrode showed electrocatalytic oxidation for MA. The synergistic effect of MWCNTs and gold nanoparticles could greatly improve the electrode performance in 0.01 M NaOH electrolyte. The cyclic voltammetric response of the proposed electrode is about 34 and 2.9 fold that of the bare SPE and MWCNTsNf/SPE, respectively. The sensor has been used for quantitative detection of MA with the 19
Page 19 of 42
SWASV and EIS owning high sensitivity. A wide linear dynamic range, good reproducibility, high stability and fast response were obtained for the determination of MA concentration. Moreover, simple preparation and low cost are some advantages of this disposable modified
ip t
electrode. From the resulting data the information on electron-transfer coefficient, rate constant of electron transfer and reversibility of the current response can be extracted. The results of the
cr
present work indicated that the proposed sensor was suitable for the detection of MA
us
concentration.
an
Acknowledgments
Financial support from the Research Affairs of Shahid Beheshti University is gratefully
ed pt
References
M
appreciated.
Ac ce
[1] C. Yi, Y. Tao, B. Wang, X. Chen, Anal. Chim. Acta 541 (2005) 75-83. [2] N. Kuroda, R. Nomura, O. Al-Dirbashi, S. Akiyama, K. Nakashima, J. Chromatogr. A 798 (1998) 325-334.
[3] M. Nishida, M. Yashiki, A. Namera, K. Kimura, J. Chromatogr. B 842 (2006) 106-110. [4] H. Kalant, Canadian Medical Association 165 (2001) 917-928. [5] C. He, C. Deng, L. Shi, Y. Fu, H. Cao, J. Cheng, Synth. Met. 161 (2011) 293-297. [6] Y. He, A. Vargas, Y.J. Kang, Anal. Chim. Acta 589 (2007) 225-230. 20
Page 20 of 42
[7] D. Djozan, M.A. Farajzadeh, S.M. Sorouraddin, T. Baheri, J. Chromatogr. A 1248 (2012) 2431.
ip t
[8] M. Yonamine, N. Tawil, R.L.M. Moreau, O.A. Silva, J. Chromatogr. B 789 (2003) 73-78. [9] H.P. Hendrickson, A. Milesi-Hallé, E.M. Laurenzana, S.M. Owens, J. Chromatogr. B 806
cr
(2004) 81-87.
us
[10] H. Dai, Y. Wang, X. Wu, L. Zhang, G. Chen, Biosens. Bioelectron. 24 (2009) 1230-1234.
an
[11] K. Yagiuda, A. Hemmi, S. Ito, Y. Asano, Biosens. Bioelectron. 11 (1996) 703-707. [12] A. Miki, T. Keller, P. Regenscheit, R. Dirnhofer, M. Tatsuno, M. Katagi, M. ishikawa, H.
M
Tsuchihashi, J. Chromatogr. B 692 (1997) 319-328.
B 749 (2000) 111-118.
ed
[13] Chinaka, S., Tanaka, S., Takayama, N., Komai, K., Ohshima, T., Ueda, K., J. Chromatogr.
pt
[14] E.M.P.J. Garrido, J.M.P.J. Garrido, N. Milhazes, F. Borges, A.M. Oliveira-Brett,
Ac ce
Bioelectrochemistry 79 (2010) 77-83.
[15] H. Yin, X. Meng, H. Su, M. Xu, S. Ai, Food Chem. 134 (2012) 1225-1230. [16] R.M. Penner, C.R. Martin, Anal. Chem. 59 (1987) 2625-2630. [17] A.R. Fakhari, B. Rafiee, H. Ahmar, A. Bagheri, Anal. Methods 4 (2012) 3314-3319. [18] S. Iijima, Nature 354 (1991) 56-58. [19] Y. Guo, S. Guo, Y. Fang, S. Dong, Electrochim. Acta 55 (2010) 3927-3931. [20] M. Pumera, Chem.—Eur. J. 15 (2009) 4970-4978. 21
Page 21 of 42
[21] N.X. Viet, Y. Ukita, M. Chikae, Y. Ohno, K. Maehashi, K. Matsumoto, P.H. Viet, B. Wang, J. Zhang, G. Cheng, S. Dong, Anal. Chim. Acta 407 (2000) 111-118.
ip t
[22] A.A. Ensafi, , A.R. Allafchian, M. Saraji, B. Farajmand, Talanta 99 (2012) 335-341.
cr
[23] M. Wojciechowski, J. Balcerzak, Anal. Chim. Acta 249 (1991) 433-445. [24] S.A. Borman, Anal. Chem. 54 (1982) 698A-705A.
us
[25] T.M. Florence, Analyst 111 (1986) 489-505.
an
[26] C. Berggren, P. Stalhandske, J. Brundell, G. Johansson, Electroanalysis 11 (1999) 156-160.
M
[27] T.K. Rout, Corrosion Science 49 (2007) 794-817.
[28] K.M. Millan, A. Saraullo, S.R. Mikkelsen, Anal. Chem. 66 (1994) 2943-2948.
ed
[29] A.G.E. Saum, R.H. Cumming, F.J. Rowell, Biosens. Bioelectron. 13 (1998) 511-518.
pt
[30] A. Nogueira, X.R. Novoa, C. Perez, Prog. Org. Coat. 59 (2007) 186-191.
Ac ce
[31] S.K. Roy, M.E. Orazem, J. Power Sources 184 (2008) 212-219. [32] J.S. Daniels, N. Pourmand, Electroanalysis 19 (2007) 1239-1257. [33] P. Sistat, A. Kozmai, N. Pismenskaya, C. Larchet, G. Pourcelly, V. Nikonenko, Electrochim. Acta 53 (2008) 6380-6390. [34] M. Bart, E.C.A. Stigter, H.R. Stapert, G.J. De Jong, W.P. van Bennekom, Biosens. Bioelectron. 21 (2005) 49-59. [35] A. Bonanni, A.H. Loo, M. Pumera, Trends Anal. Chem. 37 (2012) 12-21. 22
Page 22 of 42
[36] B. Rafiee, A.R. Fakhari, Biosens. Bioelectron. 46 (2013) 130-135. [37] K.C. Honeychurch, J.P. Hart, Trends Anal. Chem. 22 (2003) 456-469.
ip t
[38] O.D. Renedo, M.J.A. Martinez, Analy. Chim. Acta 589 (2007) 255-260.
cr
[39] P.V. Dudin, P.R. Unwin, J.V. Macpherson, J. Phys. Chem. C 114 (2010) 13241-13248.
[40] Yu.I. Golovin, D.Yu. Golovin, A.V. Shuklinov, R.A. Stolyarov, V.M. Vasyukov, Tech.
us
Phys. Lett. 37 (2011) 253-255.
an
[41] X. Chen, j. Zhu, Q. Xi, W. Yang, Sens. Actuators B 161 (2012) 648-654.
M
[42] M. Masui, H. Sayo, Y. Tsuda, Journal of Chemical Society B 9 (1968) 973-976. [43] A. Adenier, , M.M. Chehimi, I. Gallardo, J. Pinson, N. Vila, Langmuir 20 (2004) 8243-
ed
8253.
(1993) 1379-1384.
pt
[44] J.A. Squella, B.K. Cassels, M. Arata, M.P. Bavestrello, L.J. Nunez-Vergara, Talanta 40
Ac ce
[45] G. Martinez-Paredes, M.B. Gonzalez-Garcia, A. Costa-Garcia, Electrochim. Acta 54 (2009) 4801-4808.
[46] T. Hezard, K. Fajerwerg, D. Evrard, V. Colliere, P. Behra, P. Gros, Electrochim. Acta 73 (2012) 15-22.
[47] D. Yue, Y. Jia, Y. Yao, J. Sun, Y. Jing, Electrochim. Acta 65 (2012) 30-36. [48] E. Laviron, J. Electroanal. Chem. 101 (1979) 19-28. [49] L. Xiao, G.G. Wildgoose, R.G. Compton, Anal. Chim. acta 620 (2008) 44-49. 23
Page 23 of 42
[50] Q. Zhao, Y. Chai, R. Yuan, J. Luo, Sens. Actuators B 178 (2013) 379-384. [51] M.D. Levi, D. Aurbach, J. Electrochem. Soc. 149 (2000) E215.
ip t
[52] M. Shamsipur, S.H. Kazemi, M.F. Mousavi, Biosens. Bioelectron. 24 (2008) 104-110. [53] C.C.M. Martinez, E.F. Treo, R.E. Madrid, C.C. Felice, Biosens. Bioelectron. 26 (2010)
cr
1239-1244.
us
[54] M. Shamsipur, M. Asgari, M.F. Mousavi, R. Davarkhah, Electroanalysis 24 (2012) 357-367.
an
[55] D. Bethell, M. Brust, D.J. Schiffrin, C. Kiely, J. Electroanal. Chem. 409 (1996) 137-143.
Anal. Biochem. 373 (2008) 337-348.
M
[56] M. Hajjizadeh, A. Jabbari, H. Heli, A.A. Moosavi-Movahedi, A. Shafiee, K. Karimian,
ed
[57] C.C. Chou, M.R. Lee, Analy. Chim. Acta 538 (2005) 49–56. [58] Y. He, Y.J. Kang, J. Chromatogr. A 1133 (2006) 35–40.
pt
[59] O. Al-Dirbashi, N. Kuroda, S. Akiyama, K. Nakashima, J. Chromatogr. B 695 (1997) 251–
Ac ce
258.
[60] I. Koide, O. Noguchi, K. Okada, A. Yokoyama, H. Oda , S. Yamamoto, H. Kataoka, J. Chromatogr. B 707 (1998) 99–104. [61] G. Sakai, S. Nakata, T. Uda, N. Miura, N. Yamazoe, Electrochim. Acta 44 (1999) 3849– 3854.
Figure captions 24
Page 24 of 42
Fig. 1. (A) SEM images of the SPE surface modified with MWCNTs-Nf and (B) MWCNTs-
ip t
Nf/GNPs; (C) EDX spectrum of SPE/MWCNTs-Nf/GNPs surface.
Fig. 2. SEM photo and EDX mapping of SPE/MWCNTs-Nf/GNPs surface. SEM photo (a), EDX (b) and EDX mapping of gold
(c).
us
cr
mapping of carbon
Fig. 3. Cyclic voltammograms for bare SPE (a), SPE/MWCNTs-Nf (b) and SPE/MWCNTs-
M
an
Nf/GNPs (c) in 0.01 M NaOH solution containing 0.01 M MA, scan rate: 100 mVs–1.
Fig. 4. (A) Cyclic voltammograms of SPE/MWCNTs-Nf/GNPs in 0.01 M NaOH containing 5.0
ed
mM MA at different scan rates (1, 5, 10, 25, 50, 100, 125, 150 and 200 mV s–1); (B) Variation of peak current versus scan rate; (C) Dependence of the peak potential, Ep, to the logν; (D) Tafel
Ac ce
pt
Plot for modified electrode, scan rate: 1 mV s–1.
Fig. 5. SW voltammograms at the bare SPE (a), SPE/MWCNTs-Nf (b), SPE/MWCNTsNf/GNPs (c) and SPE/MWCNTs-Nf/GNPs after using –200 mV for 200 s as stripping step (d) in 0.01 M NaOH solution containing 0.1 mM MA.
25
Page 25 of 42
Fig. 6. (A) Anodic stripping determination of 0.1 mM MA in 0.01 M NaOH solution at SPE/MWCNTs-Nf/GNPs using different electrodeposition potentials (+100, 0, −100, −200,
ip t
−300, −400 mV), tdep = 200 s; (B) Chart spot of voltammograms showed in (A).
cr
Fig. 7. (A) Anodic stripping determination of 0.1 mM MA in 0.01 M NaOH solution at
an
mV; (B) Chart spot of voltammograms showed in (A).
us
SPE/MWCNTs-Nf/GNPs using different electrodeposition times from 0 to 350 s, Edep = –200
Fig. 8. Calibration curve for different MA concentration (0.02, 0.05, 0.07, 0.09, 0.1, 3, 5, 9, 15,
M
25, 35 and 50 µM) measured by SWASV after using –200 mV for 200 s in 0.01 M NaOH
ed
solution at SPE/MWCNTs-Nf/GNPs; Deposition potential: –200 mV; deposition time: 200 s; pulse amplitude: 10 mV; and pulse width: 10 ms. The insets show the relationship between Ip
Ac ce
pt
and different concentrations of MA.
Fig. 9. (A) Nyquist plots obtained at SPE/MWCNTs-Nf/GNPs for different concentration of MA in 0.01 M NaOH solution in the absence (a) and in the presence of 1.15 (b), 4.1 (c), 8.3 (d), 11.6 (e), 14.7 (f), 19 nM (g) MA. Conditions: EDC = 280 mV, frequency range of 100000 to 0.01 Hz. Symbols are the experimental data and lines show the approximated results. (B) Calibration graph of 1/Rct as a function of MA concentration.
26
Page 26 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Table 1 The effect of various foreign species on the determination of 5.0 M MA. Foreign species Tolerance limit Recovery% Uric acid 1000 99.8 ± 1.5 L-tryptophan 100 101.2 ± 3.5 Acetaminophen 100 98.8 ± 1.5 Ascorbic Acid 50 97.4 ± 1.1 Epinephrine 5 98.2 ± 3.5 Isoprenaline 1 97.3 ± 3.2
28
Page 27 of 42
ip t cr us an M ed
Table 2 Analytical parameters for detection of MA by different methods Sample
Conductivity-based immunosensor
LOD
RSD (%)
Ref.
Human urine
1–10 mg/L
0.5 mg/L
5
[11]
Serum
0.5– 200µg/L
0.04 µg/L
< 8.0
[57]
ECLg/Ru(bpy)32+
–
0.13–180 mg/L
37 µg/L
1.1
[1]
ECL/Ru(bpy)32+
Human urine
0.015– 14.8 mg/L
1.48 µg/L
3.1
[10]
Human urine
1.0–1500µg/L
0.3 µg/L
< 5.0
[6]
Human urine
10–1500 µg/L
2 µg/L
5.1
[7]
b
Ac ce
SPME–LC/ESI–MS/MS
a
LDR
pt
Method
HS–LPME /HPLC–UV
a
MISPE–DLLME–GC–FID LC/MS/MS
Rat serum
0.3–1000 µg/L
0.3 µg/L
< 5.0
[9]
LLLME c/HPLC–UV
Human urine
1.0–1500 µg/L
0.5 µg/L
< 5.0
[58]
CE–UV
Human urine
0.2–500 mg/L
0.1 mg/L
1.4
[13]
Hair
0.5–120 µg/g hair
0.5 mg/L
5.2
[12]
HPLC/Fluorescence
Human urine
4.6–1800 µg/L
1 µg/L
2.6
[59]
HS–SPME/GC–NPDf
Hair
4–160 µg/g hair
0.4 µg/g hair
< 10
[60]
Hair
250–0.63 µg /g hair
0.25 µg/g hair
–
[3]
Saliva
5–100 µg/L
0.5 µg/L
–
[8]
Human urine
0.1–1000 µg/L
100 µg/L
–
[61]
–
0.21– 0.5 µg/L
56 ng/L
–
This work
e
IMS
SPME/GC–MS
h
SPME/GC–MS i
SPR -based immunosensor SPE/MWCNTs-
EIS
Nf/GNPs j
29
Page 28 of 42
Nf/GNPs j
3.7–18 µg/L and
SWASV
1.1 µg/L
4.2
0.55–9.2 mg/L a
Solid-phase microextraction/Liquid chromatography/Electrospray ionization/Tandem mass spectrometry Headspace liquid-phase microextraction c Single drop liquid–liquid–liquid microextraction d Capillary electrophoresis e Ion mobility spectrometry f Nitrogen–phosphorus detector g Electrochemiluminescence
i
Surface-plasmon-resonance
j
Gold nanoparticles-Multiwalled carbon nanotubes-Nafion modified Screen-printed carbon electrode
cr
With one-pot derivatization
Ac ce
pt
ed
M
an
us
h
ip t
b
Scheme 1
30
Page 29 of 42
ip t cr us an M ed pt Ac ce Fig. 1
31
Page 30 of 42
B
1 µm
C
Ac ce
pt
ed
M
an
us
cr
1 µm
ip t
A
Fig. 2 32
Page 31 of 42
c
Ac ce
pt
ed
M
an
us
cr
ip t
a
Fig. 3 33
Page 32 of 42
cr
ip t
c
a
Ac ce
pt
ed
M
an
us
b
Fig. 4
34
Page 33 of 42
35
Page 34 of 42
ed
pt
Ac ce us
an
M
cr
ip t
ed
pt
Ac ce us
an
M
cr
ip t
C
36
Page 35 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Fig. 5
37
Page 36 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Fig. 6
38
Page 37 of 42
Fig. 7
Ac ce
pt
B
ed
M
an
us
cr
ip t
A
39
Page 38 of 42
Ac ce
pt
ed
M
an
us
cr
ip t
Fig. 8
40
Page 39 of 42
Fig. 9
ed
M
an
us
cr
ip t
A
Ac ce
pt
B
41
Page 40 of 42
Authers Biography Ali Reza Fakhari received his B.S. degree at Tarbiat Moalem University in 1988, M.S. degree at Shiraz University in 1991 and Ph.D. in Analytical Chemistry at Tarbiat Modarres University,
ip t
Tehran, Iran in 1997. His Ph.D. supervisor was Professor Mojtaba Shamsipur. He has got associate professor since 2003 and professorship since 2008. He has been supervisor of 38 M.S.
cr
and 6 Ph.D. students. His current research activities include chemical and biochemical sensors,
us
electro-organic synthesis, capillary electrophoresis and other separation methods.
an
Banafsheh Rafiee received her B.S. degree in Applied Chemistry in 2005, M.S. degree in Analytical Chemistry at K.N. Toosi University of Technology in 2008 and Ph.D. degree in
M
Department of Chemistry at Shahid Beheshti University (Tehran, Iran) in 2013. Her research
different applications.
ed
interest mainly focuses on the use of nanomaterials based sensors (chemical and biochemical) for
pt
Mohammad Ghaffarzadeh obtained his B.S. in pure chemistry in 1993 from Tabriz University.
Ac ce
He completed his M.S. in Organic Chemistry in Sharif University of Technology in 1996. After completing his Ph.D. in the same university in 2001, he joined the Chemistry and Chemical Engineering Research Center of Iran (CCERCI), Tehran, as an assistant professor. His research interests focus on organic syntheses methodology, new drug design & synthesis and scale-up of organic reactions.
42
Page 41 of 42
Ac
ce
pt
ed
M
an
us
cr
i
Graphical Abstract (for review)
Page 42 of 42