- Email: [email protected]
Fabrication of electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan–copper complex by self-assembly technique
Talanta 144 (2015) 252–257
Contents lists available at ScienceDirect
Talanta journal homepage: www.elsevier.com/locate/talanta
Fabrication of electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan–copper complex by self-assembly technique Airong Mao a,b, Hongbo Li b, Dangqin Jin a,c, Liangyun Yu a,b, Xiaoya Hu a,n a
School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China School of Chemistry and Chemical Engineering, Yancheng Institute of Technology, Yancheng 224051, China c Department of Chemical Engineering, Yangzhou Polytechnic Institute, Yangzhou 225127, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 21 April 2015 Received in revised form 4 June 2015 Accepted 7 June 2015 Available online 11 June 2015
An electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan– copper complex (MWCNTs/CTS–Cu) was fabricated by self-assembly technique. The MWCNTs/CTS–Cu modified GCE showed an excellent electrocatalytic activity for the oxidation of paracetamol, and accelerated electron transfer between the electrode and paracetamol. Under optimal experimental conditions, the differential pulse peak current was linear with the concentration of paracetamol in the range of 0.1–200 μmol L 1 with a detection limit of 0.024 μmol L 1. The sensitivity was found to be 0.603 A/mol L 1. The proposed sensor also showed a high selectivity for paracetamol in the presence of ascorbic acid and dopamine. Moreover, the proposed electrode revealed good reproducibility and stability. The proposed method was successfully applied for the determination of paracetamol in tablet and human serum samples. & 2015 Elsevier B.V. All rights reserved.
Keywords: Self-assembly Paracetamol Multi-walled carbon nanotubes Chitosan Copper
1. Introduction Paracetamol is an antipyretic and analgesic drug commonly used for fever, headaches, and minor pain relief [1]. At therapeutic doses, paracetamol is generally considered safe and effective compared to other nonsteroidal analgesics. However, overdoses of paracetamol produce the accumulation of toxic metabolites, which may cause severe and sometimes fatal hepatoxicity and nephrotoxicity [2]. Hence, it is of great importance to develop a simple, fast, sensitive and precise procedure for paracetamol overdose diagnosis. So far, various analytical methods including chromatography [3], spectrophotometry [4], capillary electrophoresis [5], chemiluminescence [6] and flow-injection analysis [7] have been reported for the determination of paracetamol. However, these methods are generally time-consuming and require laborious sample pretreatment. Recently, electrochemical techniques have received tremendous attention on detection of paracetamol due to their merits of high selectivity, simple pretreatment procedure, less time-consuming and low cost [8–16]. Despite these advances, it is still a great challenge to construct highly selective, sensitive and stable nonenzymatic n
Corresponding author. Fax: þ86 514 87311374. E-mail address: [email protected] (X. Hu).
http://dx.doi.org/10.1016/j.talanta.2015.06.020 0039-9140/& 2015 Elsevier B.V. All rights reserved.
electrochemical sensors for the determination of paracetamol. Carbon nanotubes (CNTs) have been widely applied to fabricate high performance electrochemical sensors [17,18]. Carbon nanotubes have become extremely attractive since their discovery in 1991 [19]. CNTs possess many unique properties such as good electrical conductivity, high electrocatalytic effect, strong adsorptive ability and excellent biocompatibility [20]. Owing to these properties, many studies on sensors for paracetamol based on CNTs have been reported in the past few decades [21–29]. However, the sensitivity of these reported methods is not high enough. So, it is necessary to develop a kind of sensors for paracetamol detection with higher sensitivity. Chitosan (CTS) is a linear copolymer of d-glucosamine and N-acetyl-d-glucosamine. In its linear polyglucosamine chains of high molecular weight, chitosan has reactive amino and hydroxyl groups which make it show excellent adsorption capacity toward heavy metal cations and organics [30]. Moreover, chitosan shows many unique properties, such as biocompatibility, biodegradation, biological activity, low toxicity, film forming ability and so on [31]. Based on the above advantages, sensors based on chitosan matrix have been developed to detect paracetamol [32–34]. Moreover, complexes of transition metals immobilized on polymeric matrices are promising ecologically friendly catalysts due to the favorable combination of the properties of homogeneous and heterogeneous systems [35]. The chitosan metal complexes have annulus chelating structure and
A. Mao et al. / Talanta 144 (2015) 252–257
possess the characteristic of natural enzymes, so they exhibit favorable catalytic activity for many chemical reactions. A chitosan– nickel modified carbon paste electrode was rendered to be a capable electrode for electrooxidation of formaldehyde [36]. Zhao and co-workers reported a chitosan–copper complex modified electrode to detect hydrogen peroxide [37]. Yu and co-workers established a nonenzymatic sensor based on chitosan–copper complexes modified multi-walled carbon nanotubes ionic liquid electrode to measure H2O2 [38]. But so far, electrochemical sensors for paracetamol detection based on chitosan–copper complexes or chitosan–nickel complexes have not been reported. Herein, we reported a novel electrochemical sensor based on multi-walled carbon nanotubes (MWCNTs) and chitosan–copper complexes (CTS–Cu) for sensitive determination of paracetamol. The MWCNTs/CTS–Cu modified glassy carbon electrode (GCE) was fabricated by self-assembly technique. Effective parameters on response of the proposed sensor were investigated in details. Finally, the sensor was used for determination of paracetamol in tablet and human serum samples.
2. Experiments 2.1. Meterials and instrumentations Multi-walled carbon nanotubes (MWCNTs) were obtained from Nanjing Jicang Nano Technology Co., Ltd (China). Paracetamol, chitosan(CTS) and CuCl2 2H2O were purchased from Aladdin reagent Co., Ltd. (China). All other reagents were of analytical grade and used without further purification. Ultra-pure water (resistivity no less than 18 MΩ cm) was used for preparation of buffer and standard solutions. A stock solution of 0.1 mol L 1 paracetamol was prepared by diluting paracetamol in 25% ethanol solution. Test standard solutions were prepared daily by appropriate dilution of the stock solution. 0.2 mol L 1 phosphate buffer solutions (PBS) with different pH values were prepared by mixing stock standard solutions of Na2HPO4 and NaH2PO4. All electrochemical studies were performed with a CHI 660B electrochemical workstation (Shanghai Chenhua Instrument Company, China). A conventional three-electrode system was used, consisting of a saturated calomel electrode (SCE) as reference electrode, a platinum foil electrode as counter electrode, and a bare or modified glassy carbon electrode (diameter 3 mm) as working electrode. A magnetic stirrer and a stirring bar provided the convective transport during the amperometric studies. A 0.2 mol L 1 phosphate buffer solution (pH 7.0) was used as supporting electrolyte. All experiments were carried out at room temperature (25 °C). The morphology of different modified electrodes was characterized by a S4800 field-emission scanning electron microscope (Hitachi company, Japan). 2.2. Purification of MWCNTs The MWCNTs were purified according to literature [23]. Firstly, the MWCNTs were heated in air at 600 °C for 2 h, and then soaked in 6 mol L 1 HCl solution for 24 h and centrifuged. The precipitate was rinsed with ultra-pure water and dried under air. Secondly, the MWCNTs were chemically functionalized by ultrasonic agitation in a mixture of sulfuric and nitric acid (3:1) for 8 h. Subsequently, the MWCNTs were filtered, washed with ultra-pure water until pH 7.0 was reached, and then dried at 120 °C for 5 h. Then the multi-walled carbon nanotube functionalized with carboxyl group was obtained.
253
2.3. Preparation of modified electrode A glassy carbon electrode (GCE, diameter 3 mm) was polished to a mirrorlike surface with 1.0, 0.3 and 0.05 μm alumina slurry on silk, respectively. Subsequently, the electrode was rinsed with 1:1 HNO3–H2O (V/V), ethanol and double distilled water in an ultrasonic bath for 2–3 min each wash and air-dried at room temperature [37]. 100 mg MWCNTs were dispersed in 50 mL ultrapure water, and then the mixture was sonicated for 15 min until a black suspension was formed. Chitosan solution was prepared by dissolving 0.25 g chitosan solid in 50 mL 0.10 mol L 1 acetic acid. A copper solution was prepared by dissolving 0.1 g CuCl2 2H2O in 100 mL ultrapure water. The MWCNTs/CTS–Cu modified GCE was fabricated according to the following procedure. Firstly, the MWCNTs modified electrode(MWCNTs/GCE) was prepared by coating the surface of GCE with 5 μL MWCNTs suspension, and then air-dried at room temperature. Secondly, the MWCNTs/GCE was dipped into the chitosan solution for 30 min, and the positive charged chitosan was self-assembled onto the negatively charged MWCNTs functionalized with carboxyl group through the electrostatic interactions. The MWCNTs/CTS/GCE was taken out and rinsed with ultra-pure water. Finally, the MWCNTs/CTS/GCE was dipped into the copper solution for 30 min, and the Cu2 þ was self-assembled onto the chitosan through the complexing actions. The proposed MWCNTs/ CTS–Cu /GCE was taken out, rinsed with ultra-pure water, and then air-dried at room temperature before measurement. The schematic illustration of the process for preparation of MWCNTs/ CTS–Cu/GCE was showed in Fig. 1. 2.4. Analytical procedure Paracetamol was successfully added into an electrochemical cell containing 50 mL 0.2 mol L 1 PBS (pH 7.0) as supporting electrolyte. The electrochemical behaviors of paracetamol on different modified electrodes were studied by cyclic voltammetry (CV), and the concentrations of paracetamol were quantitatively analyzed by differential pulse voltammetry (DPV). The DPV curves were recorded in the potential range from 0.0 V to 0.6 V, with scan rate of 0.1 V s 1, amplitude of 0.05 V, pulse width of 0.05 s and quiet time of 2 s. All measurements were performed at room temperature. During preconditioning, the solution was efficiently stirred.
3. Results and discussion 3.1. Characterization of MWCNTs/CTS–Cu/GCE SEM technique was utilized to characterize the surface morphologies of the fabricated sensors. The SEM image of MWCNTs/GCE (Fig. 2A) displayed a typical morphology of the MWCNTs. From the SEM image of MWCNTs/CTS–Cu/GCE (Fig. 2B), we can obviously see the morphology of the chitosan film except the typical morphology of MWCNTs. The results indicated that the MWCNTs/CTS–Cu complexes were successfully prepared and modified onto the surface of GCE. The MWCNTs/CTS–Cu composites formed a compact film covering the surface of GCE, which increased the specific surface area of the electrode and was conducive to the adsorption of paracetamol. 3.2. Electrochemical behavior of paracetamol on MWCNTs/ CTS–Cu/ GCE Cyclic voltammograms were used to investigate the electrochemical behavior of paracetamol on bare GCE, MWCNTs/GCE and
254
A. Mao et al. / Talanta 144 (2015) 252–257
Fig. 1. Schematic illustration of the process for preparation of MWCNTs/CTS–Cu/GCE.
MWCNTs/CTS–Cu/GCE. Only one oxidation peak was observed in Fig. 3a, indicating that paracetamol demonstrated an irreversible redox behavior on the bare GCE. In contrast, a pair of well-defined redox peaks were obtained in Fig. 3b and c. The results suggested that paracetamol displayed a quasi-reversible redox behavior on the MWCNTs/GCE and MWCNTs/CTS–Cu/GCE. Moreover, the oxidation peak potential significantly shifted to the negative direction, and the oxidation peak current obtained on the MWCNTs/ CTS–Cu/GCE was nearly seven times larger than that obtained on the bare GCE. This was because the MWCNTs and chitosan–copper complexes promoted the electron transfer between paracetamol and the modified electrode, and showed attractive electrocatalytic properties for paracetamol [33–35]. On the other hand, the chitosan could improve the dispersion performance of MWCNTs. Hence, the proposed MWCNTs/CTS–Cu/GCE was selected for further studies on paracetamol detection. 3.3. Effect of scan rate The effect of scan rates on the redox peak currents was investigated in the range of 10–400 mV s 1. Fig. 4 showed the cyclic
voltammograms of paracetamol on the MWCNTs/CTS–Cu/GCE at different scan rates. The results indicated that the redox peak currents increased with the increase of scan rate increasing from 10 to 400 mV s 1. Inset of Fig. 4 showed that both the oxidation and reduction peak currents were linearly proportional to the scan rates in the range of 10–400 mV s 1. The linear regression equations are Ipa (μA)¼(4.168 70.200) þ(0.16270.008)ν(mV s 1) (R¼ 0.999) and Ipc (μA)¼( 0.13370.006) þ (0.1017 0.005) ν(mV s 1) (R¼ 0.997), indicating that the electrochemical reaction of paracetamol on the modified electrode was a surface-controlled process [23]. 3.4. Effect of pH value The effect of pH value on the anodic peak currents of the MWCNTs/CTS–Cu/GCE was studied in the pH range of 5.7–8.0. As shown in Fig. 5, the peak potentials shifted negatively with the pH value increasing from 5.7 to 8.0, which indicated that the redox reaction involved the protons [21]. The anodic peak currents increased with the pH value increasing from 5.7 to 7.0, and then decreased with the pH value increasing from 7.0 to 8.0, suggesting
Fig. 2. SEM images of MWCNTs/GCE (A) and MWCNTs/CTS–Cu/GCE (B).
A. Mao et al. / Talanta 144 (2015) 252–257
Fig. 3. Cyclic voltammograms 1.0 10 5 mol L 1 paracetamol on bare GCE (a), MWCNTs/GCE (b) and MWCNTs/CTS–Cu/GCE (c) in 0.2 mol L 1 phosphate buffer solution (pH 7.0) as supporting electrolyte at a scan rate of 0.1 V s 1.
255
Fig. 5. Cyclic voltammograms of 1.0 10 5 mol L 1 paracetamol on the MWCNTs/ CTS–Cu/GCE in the pH range of 5.7 to 8.0 (from right to left) at a scan rate of 0.1 V s 1. Inset is the plot of the anodic peak potential against pH.
3.5. Effect of deposition potential and deposition time
Fig. 4. Cyclic voltammograms of 1.0 10 5 mol L 1 paracetamol on the MWCNTs/ CTS–Cu/GCE at different scan rates of 10, 25, 50, 75, 100, 125, 150, 175, 200, 250, 300 and 400 mV s 1 (from inner to outer) in 0.2 mol L 1 phosphate buffer solution (pH 7.0) as supporting electrolyte. Inset is the plot of the peak currents vs. scan rates.
that the oxidation reaction of paracetamol was kinetically less favorable at higher pH [15]. But paracetamol was hydrolyzed to p-aminophenol at very low pH values [27].The maximum peak current was obtained at pH 7.0. Hence, the 0.2 mol L 1 PBS (pH 7.0) was chosen as supporting electrolyte in the subsequent experiments. Inset of Fig. 5 showed that the anodic peak potentials of paracetamol were proportional to the pH. Linear regression equation was obtained as Epa (V) ¼0.8091–0.0628 pH (R ¼0.999). According to the slope (0.0628) and the formula Ep ¼K (0.057)m/ npH, m/n was figured out as 1. Furthermore, the redox potential difference (ΔEp) was 0.32 mV. So the electron transfer number was figured out as 2 according to the formula n ¼58/ΔEp. In conclusion, the reaction of paracetamol on the MWCNTs/CTS–Cu/ GCE was a two-electron and two-proton quasi-reversible process. The anodic peak at 0.367 V was ascribed to the oxidation of paracetamol to form N-acetyl-p-quinone imine, and the reduction peak reduction at 0.325 V was ascribed to the reduction of paracetamol to form N-acetyl-p-quinone imine. The possible reaction equation was described as follows:
With the purpose of improving sensitivity, the effect of the deposition potential and deposition time on the response of paracetamol on the MWCNTs/CTS–Cu/GCE was investigated during preconditioning process (see Fig. 6). The influence of the deposition potential on the anodic peak currents of 1.0 10 5 mol L 1 paracetamol was investigated when the deposition time was fixed for 60 s. When the deposition potential shifted negatively from 0.0 to 0.6 V, the anodic peak currents increased. When more negative potentials were applied, the peak currents were essentially unchanged. Therefore, a deposition potential of 0.6 V was chosen for further experiments.The influence of the deposition time on the anodic peak currents of 1.0 10 5 mol L 1 paracetamol was investigated at a fixed deposition potential of 0.6 V. Deposition time was the most important factor for determination of the detection limit in voltammetric analysis. When the deposition time varied in the range of 30–180 s, the peak current increased with the increase of deposition time. When the deposition time increased from 180 s to 240 s, the peak current remained increased slightly. This was because at the same deposition potential, a longer deposition time would make paracetamol be reduced more completely. Subsequently, it would lead to a higher peak current. However, when the deposition time was extremely long, the reduced paracetamol covered the entire effective electrode surface, and the peak current did not change. Therefore, a deposition time of 180 s was chosen for further experiments. 3.6. Analytical characterization Under the optimal experimental conditions, the successive determination of paracetamol on the MWCNTs/CTS–Cu/GCE was carried out in 0.2 mol L 1 phosphate buffer solution by differential
256
A. Mao et al. / Talanta 144 (2015) 252–257
pulse voltammetry (DPV). Fig. 7 showed the DPVs of various concentration of paracetamol ranging from 0.1 to 200 μmol L 1. It could be seen that the anodic peak currents increased with the increase of the concentration of paracetamol, and the anodic peak current (Ip) was linear with the concentration of paracetamol. The calibration plot of the DPV peak current vs. the concentration of paracetamol was shown in the inset of Fig. 6. When the concentration of paracetamol were in the range of 0.1 to 200 μmol L 1, the linear regression equation was Ip (μA)¼ 0.377þ 0.603c (μmol L 1) (R ¼0.999). The detection limit was found to be 0.024 μmol L 1, and the sensitivity was 0.603 A/mol L 1 on signal-to-noise of 3. The comparison of MWCNTs/CTS–Cu/GCE with other modified electrodes for paracetamol detection was listed in Table 1. It can be seen that the MWCNTs/CTS–Cu/GCE offered the widest linear range among the previous methods. Moreover, the detection limit was lower than most of previous reports. The results indicate that the proposed MWCNTs/CTS–Cu/GCE is reliable for the detection of paracetamol. Paracetamol generally suffers from the interference of ascorbic acid (AA) and dopamine (DA) in biological samples [21]. Hence, a systematic study of interference of ascorbic acid and dopamine was carried out to evaluate the selectivity of the proposed sensor. Fig. 8 was the differential pulse voltammogram of AA, DA and paracetamol with equal concentration in a mixture on the MWCNTs/CTS–Cu/GCE, indicating that paracetamol exhibited well-defined DPV wave with good separation from equal concentration AA and DA. The further results showed that 100-fold of Table 1 Comparison of different modified electrodes for paracetamol detection. Electrodes
Methods Linear range Detection lim(nM) it (nM)
References
Poly(L-glutamic)/GCE
DPV
30
[14]
92
[23]
1.0 113
[26] [27]
97 0.09 24
[28] [29] This work
(MWCNTs/NHCH2)6/GCE DPV CoNPs/MWCNTs/GCE MWCNTs/GNS/ GCE
SWV DPV
MWCNTs/polyhis/ GCE MWCNTs/GCE MWCNTs/CTS–Cu/GCE
DPV DPV DPV
100– 140,000 1000– 200,000 5.2–450 480– 215,000 250–5000 0.2–15,000 100– 200,000
Table 2 Determination of paracetamol in tablet samples (n¼ 6). Sample
Labeled (mg/ tablet)
Tablet 1 160 Tablet 2 250 Tablet 3 500
Found (mg/ tablet)
Recovery (%) RSD (%) HPLC (mg)
159.1 248.5 495.8
99.40 98.40 99.20
3.02 2.10 1.86
160.7 251.1 501.9
Table 3 Results of recovery test of paracetamol in human serum samples (n ¼6). Added (μM) 0 10 50 100 a
Not detected.
Found (μM) a
ND 9.99 49.52 98.54
Recovery (%)
RSD (%)
HPLC (μM)
– 99.90 99.04 98.54
– 1.99 2.24 2.62
NDa 10.21 50.46 98.28
ascorbic acid and dopamine did not interfere with the DPV signal of 1.0 μmol L 1 paracetamol (peak current change o 75). Therefore, the sensor could be used to determinate paracetamol in biological samples for its excellent selectivity. A successful sensor primarily requires good reproducibility and stability. The reproducibility of the MWCNTs/CTS–Cu/GCE were investigated by the measurement of the DPV responses to 1.0 10 5 mol L 1 paracetamol. The results showed that the relative standard deviation (RSD) of the anodic peak currents by six successive measurements was 1.84%. The fabrication reproducibility was estimated on five different modified electrodes which were fabricated independently under the same conditions, and the RSD was found to be 3.46%. The above results revealed good reproducibility and stability of the MWCNTs/CTS–Cu/GCE. In addition, the peak current of paracetamol on the MWCNTs/CTS–Cu/ GCE retained 92% of its initial value after the storage of one week in a refrigerator at 4 °C when not in use, and then became 84% of its initial value after the storage of one month. The results suggested that the MWCNTs/CTS–Cu/GCE possessed an acceptable storage stability. 3.7. Recovery test and analytical results of real samples The proposed method was applied to determinate paracetamol in tablet and human serum samples and verify its potential application. To evaluate the applicability of the proposed sensor, the recovery of paracetamol was carried out in the spiked samples of tablet and human serum. The human serum samples were collected from nearby hospital. The serum sample was centrifuged before the determination. The spiked sample was composed of 1% human serum and known amounts of paracetamol in 0.2 M PBS. The results (see Tables 2 and 3) indicated that the recovery of paracetamol on the MWCNTs/CTS–Cu/GCE was satisfactory. Moreover, the detection values of paracetamol were in a good accordance with those obtained by HPLC method.
4. Conclusion In this work, we have developed a new modified glassy carbon electrode based on MWCNTs/CTS–Cu complexes for paracetamol determination. The proposed sensor showed an excellent selectivity for paracetamol in the presence of common potential interfering substances such as ascorbic acid and dopamine, with a wide linear range and high sensitivity. Moreover, the results revealed a good reproducibility and stability of the MWCNTs/CTS– Cu/GCE. With the above excellent performance, the proposed electrode could be used for efficient determination of paracetamol in tablet and human serum samples.
Acknowledgments The authors gratefully acknowledge the financial support from National Natural Science Foundation of China (21275124 and 21305123), National Natural Science Foundation of Jiangsu Province (BK2012247) and Foundation of Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province (AE201162).
References [1] M. Mazer, J. Perrone, Acetaminophen-induced nephrotoxicity: pathophysiology, clinical manifestations, and management, J. Med. Toxicol. 4 (2008) 2–6. [2] M.T. Olaleye, B.T.J. Rocha, Acetaminophen-induced liver damage in mice:
A. Mao et al. / Talanta 144 (2015) 252–257
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19] [20]
[21]
effects of some medicinal plants on the oxidative defense system, Exp. Toxicol. Pathol. 59 (2008) 319–327. A. Goyal, S. Jain, Simultaneous estimation of paracetamol, chlorzoxazone and diclofenac sodium in pharmaceutical formulation by a novel HPLC method, Acta Pharm. Sci. 49 (2007) 147–151. K. Sirajuddin, R. Abdul, A. Shah, M.I. Bhanger, A. Niaz, S. Mahesar, Simpler spectrophotometric assay of paracetamol in tablets and urine samples, Spectrochim. Acta A 68 (2007) 747–751. M.E. Capella-Peiró, D. Bose, M.F. Rubert, J. Esteve-Romero, Optimization of a capillary zone electrophoresis method by using a central composite factorial design for the determination of codeine and paracetamol in pharmaceuticals, J. Chromatogr. B 839 (2006) 95–101. D.L. Oldair, Determination of paracetamol using a flow injection analysis with multi commutation and chemiluminescence detection, Quim. Nova 32 (2009) 1755–1759. C.S. Wesley, P.F. Pereira, M.C. Marra, A simple strategy for simultaneous determination of paracetamol and caffeine using flow injection analysis with multiple pulse amperometric detection, Electroanalysis 23 (2011) 2764–2770. J. Luo, J.J. Cong, R.X. Fang, X.M. Fei, X.Y. Liu, One-pot synthesis of a graphene oxide coated with an imprinted sol–gel for use in electrochemical sensing of paracetamol, Microchim. Acta 181 (2014) 1257–1266. G.C. Yang, L. Wang, J.B. Jia, D.F. Zhou, D.F. Li, Chemically modified glassy carbon electrode for electrochemical sensing paracetamol in acidic solution, J. Solid State Electrochem. 16 (2012) 2967–2977. A. Babaei, B. Khalilzadeh, M. Afrasiabi, A new sensor for the simultaneous determination of paracetamol and mefenamic acid in a pharmaceutical preparation and biological samples using copper(II) doped zeolite modified carbon paste electrode, J. Appl. Electrochem. 40 (2010) 1537–1543. H.S. Yin, K. Shang, X.M. Meng, S.Y. Ai, Voltammetric sensing of paracetamol, dopamine and 4-aminophenol at a glassy carbon electrode coated with gold nanoparticles and an organophillic layered double hydroxide, Microchim. Acta 175 (2011) 39–46. A.R. Khaskheli, J. Fischer, J. Barek, V. Vyskočil, Sirajuddin, M.I. Bhanger, Differential pulse voltammetric determination of paracetamol in tablet and urine samples at a micro-crystalline natural graphite-polystyrene composite film modified electrode, Electrochim. Acta 101 (2013) 238–242. Y. Fan, J.H. Liu, H.T. Lu, Q. Zhang, Electrochemical behavior and voltammetric determination of paracetamol on Nafion/TiO2-graphene modified glassy carbon electrode, Colloid Surf. B 85 (2011) 289–292. Y. Zhang, L.Q. Luo, Y.P. Ding, X. Liu, Z.Y. Qian, A highly sensitive method for determination of paracetamol by adsorptive stripping voltammetry using a carbon paste electrode modified with nanogold and glutamic acid, Microchim. Acta 171 (2010) 133–138. H. Ghadimi, R.M.A. Tehrani, A.S.M. Ali, N. Mohamed, S.A. Ghani, Sensitive voltammetric determination of paracetamol by poly(4-vinylpyridine)/multiwalled carbon nanotubes modified glassy carbon electrode, Anal. Chim. Acta 765 (2013) 70–76. S.S. Nair, S.A. John, T. Sagara, Simultaneous determination of paracetamol and ascorbic acid using tetraoctylammonium bromide capped gold nanoparticles immobilized on 1,6-hexanedithiol modified Au electrode, Electrochim. Acta 54 (2009) 6837–6843. D. Vairavapandian, P. Vichchulada, M.D. Lay, Preparation and modification of carbon nanotubes: Review of recent advances and applications in catalysis and sensing, Anal. Chim. Acta 626 (2008) 119–129. A. Merkoci, M. Pumera, X. Llopis, B. Perez, M. del Valle, S. Alegret, New materials for electrochemical sensing. VI: carbon nanotubes, Trends Anal. Chem., 24, (2005) 826–838. S. Iijima, Helical microtubules of graphitic carbon, Nature 354 (1991) 56–58. X.M. Ren, C.L. Chen, M. Nagatsub, X.K. Wang, Carbon nanotubes as adsorbents in environmental pollution management: a review, Chem. Eng. J. 170 (2011) 395–410. J.M. Hui, W.J. Li, Y.L. Guo, Z. Yang, Y.X. Wang, C. Yu, Electrochemical sensor for
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30] [31] [32]
[33]
[34]
[35] [36]
[37]
[38]
257
sensitive detection of paracetamol based on novel multi-walled carbon nanotubes-derived organic–inorganic material, Biosyst. Eng. 37 (2014) 461–468. R.N. Goyal, V.K. Gupta, S. Chatterjee, Voltammetric biosensors for the determination of paracetamol at carbon nanotube modified pyrolytic graphite electrode, Sens. Actuators B 149 (2010) 252–258. Y.C. Li, S.Q. Feng, S.X. Li, Y.Y. Zhang, Y.M. Zhong, A high effect polymer-free covalent layer by layer self-assemble carboxylated MWCNTs films modified GCE for the detection of paracetamol, Sens. Actuators B 190 (2014) 999–1005. A. Babaei, M. Sohrabi, A.R. Taheri, Highly sensitive simultaneous determination of L-dopa and paracetamol using a glassy carbon electrode modified with a composite of nickel hydroxide nanoparticles/multi-walled carbon nanotubes, J. Electroanal. Chem. 698 (2013) 45–51. T.C. Canevari, P.A. Raymundo-Pereira, R. Landers, E.V. Benvenutti, S.A. S. Machado, Sol–gel thin-film based mesoporous silica and carbon nanotubes for the determination of dopamine, uricacid and paracetamol in urine, Talanta 116 (2013) 726–735. A. Kutluay, M. Aslanoglu, An electrochemical sensor prepared by sonochemical one-pot synthesis of multi-walled carbon nanotube-supported cobalt nanoparticles for the simultaneous determination of paracetamol and dopamine, Anal. Chim. Acta 839 (2014) 59–66. M. Arvand, T.M. Gholizadeh, Simultaneous voltammetric determination of tyrosine and paracetamol using a carbon nanotube-graphene nanosheet nanocomposite modified electrode inhuman blood serum and pharmaceuticals, Colloid, Surf. B 103 (2013) 84–93. P.R. Dalmasso, M.L. Pedano, G.A. Rivas, Electrochemical determination of ascorbic acid and paracetamol in pharmaceutical formulations using a glassy carbon electrode modified with multi-wall carbon nanotubes dispersed in polyhistidine, Sens. Actuators B 173 (2012) 732–736. A. Kutluay, M. Aslanoglu, Modification of electrodes using conductive porous layers to confer selectivity for the voltammetric detection of paracetamol in the presence of ascorbic acid, dopamine and uric acid, Sens. Actuators B 185 (2013) 398–404. H.H.M. Barikani, Applications of biopolymers I: chitosan, Monatsh. Chem. 140 (2009) 1403–1420. Q.P. Song, Z. Zhang, J.G. Gao, Synthesis and property studies of N-carboxymethyl chitosan, J. Appl. Polym. Sci. 119 (2011) 3283–3285. F. Godoy Delolo, C. Rodrigues, M. Martins, A new electrochemical sensor containing a film of chitosan-supported ruthenium: detection and quantification of sildenafil citrate and acetaminophen, J. Braz. Chem. Soc. 25 (2014) 550–552. S. Kianipour, A. Asghari, Room temperature ionic liquid/multiwalled carbon nanotube/chitosan-modified glassy carbon electrode as a sensor for simultaneous determination of ascorbic acid, uric acid, acetaminophen, and mefenamic acid, IEEE Sens. J. 13 (2013) 2690–2698. A. Babaei, M. Afrasiabi, M. Babazadeh, A glassy carbon electrode modified with multiwalled carbon nanotube/chitosan composite as a new sensor for simultaneous determination of acetaminophen and mefenamic acid in pharmaceutical preparations and biological samples, Electroanalysis 22 (2010) 1743–1749. E. Guibal, Heterogeneous catalysis on chitosan-based materials: a review, Prog. Polym. Sci. 30 (2005) 71–109. S.K.H. Darzi, A novel, effective and low cost catalyst for formaldehyde electrooxidation based on nickel ions dispersed onto chitosan-modified carbon paste electrode for fuel cell, J. Electroceram. 33 (2014) 252–263. X.J. Zhao, Z. Dai, X.Y. Zou, Investigation on electrocatalytic performance of chitosan-copper complex modified electrode to hydrogen peroxide, J. Instrum. Anal. 30 (2011) 425–429. Q. Yu, Z.H. Shi, X.Y. Liu, S.L. Luo, W.Z. Wei, A nonenzymatic hydrogen peroxide sensor based on chitosan-copper complexes modified multi-wall carbon nanotubes ionic liquid electrode, J. Electroanal. Chem. 655 (2011) 92–95.
Contents lists available at ScienceDirect
Talanta journal homepage: www.elsevier.com/locate/talanta
Fabrication of electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan–copper complex by self-assembly technique Airong Mao a,b, Hongbo Li b, Dangqin Jin a,c, Liangyun Yu a,b, Xiaoya Hu a,n a
School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China School of Chemistry and Chemical Engineering, Yancheng Institute of Technology, Yancheng 224051, China c Department of Chemical Engineering, Yangzhou Polytechnic Institute, Yangzhou 225127, China b
art ic l e i nf o
a b s t r a c t
Article history: Received 21 April 2015 Received in revised form 4 June 2015 Accepted 7 June 2015 Available online 11 June 2015
An electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan– copper complex (MWCNTs/CTS–Cu) was fabricated by self-assembly technique. The MWCNTs/CTS–Cu modified GCE showed an excellent electrocatalytic activity for the oxidation of paracetamol, and accelerated electron transfer between the electrode and paracetamol. Under optimal experimental conditions, the differential pulse peak current was linear with the concentration of paracetamol in the range of 0.1–200 μmol L 1 with a detection limit of 0.024 μmol L 1. The sensitivity was found to be 0.603 A/mol L 1. The proposed sensor also showed a high selectivity for paracetamol in the presence of ascorbic acid and dopamine. Moreover, the proposed electrode revealed good reproducibility and stability. The proposed method was successfully applied for the determination of paracetamol in tablet and human serum samples. & 2015 Elsevier B.V. All rights reserved.
Keywords: Self-assembly Paracetamol Multi-walled carbon nanotubes Chitosan Copper
1. Introduction Paracetamol is an antipyretic and analgesic drug commonly used for fever, headaches, and minor pain relief [1]. At therapeutic doses, paracetamol is generally considered safe and effective compared to other nonsteroidal analgesics. However, overdoses of paracetamol produce the accumulation of toxic metabolites, which may cause severe and sometimes fatal hepatoxicity and nephrotoxicity [2]. Hence, it is of great importance to develop a simple, fast, sensitive and precise procedure for paracetamol overdose diagnosis. So far, various analytical methods including chromatography [3], spectrophotometry [4], capillary electrophoresis [5], chemiluminescence [6] and flow-injection analysis [7] have been reported for the determination of paracetamol. However, these methods are generally time-consuming and require laborious sample pretreatment. Recently, electrochemical techniques have received tremendous attention on detection of paracetamol due to their merits of high selectivity, simple pretreatment procedure, less time-consuming and low cost [8–16]. Despite these advances, it is still a great challenge to construct highly selective, sensitive and stable nonenzymatic n
Corresponding author. Fax: þ86 514 87311374. E-mail address: [email protected] (X. Hu).
http://dx.doi.org/10.1016/j.talanta.2015.06.020 0039-9140/& 2015 Elsevier B.V. All rights reserved.
electrochemical sensors for the determination of paracetamol. Carbon nanotubes (CNTs) have been widely applied to fabricate high performance electrochemical sensors [17,18]. Carbon nanotubes have become extremely attractive since their discovery in 1991 [19]. CNTs possess many unique properties such as good electrical conductivity, high electrocatalytic effect, strong adsorptive ability and excellent biocompatibility [20]. Owing to these properties, many studies on sensors for paracetamol based on CNTs have been reported in the past few decades [21–29]. However, the sensitivity of these reported methods is not high enough. So, it is necessary to develop a kind of sensors for paracetamol detection with higher sensitivity. Chitosan (CTS) is a linear copolymer of d-glucosamine and N-acetyl-d-glucosamine. In its linear polyglucosamine chains of high molecular weight, chitosan has reactive amino and hydroxyl groups which make it show excellent adsorption capacity toward heavy metal cations and organics [30]. Moreover, chitosan shows many unique properties, such as biocompatibility, biodegradation, biological activity, low toxicity, film forming ability and so on [31]. Based on the above advantages, sensors based on chitosan matrix have been developed to detect paracetamol [32–34]. Moreover, complexes of transition metals immobilized on polymeric matrices are promising ecologically friendly catalysts due to the favorable combination of the properties of homogeneous and heterogeneous systems [35]. The chitosan metal complexes have annulus chelating structure and
A. Mao et al. / Talanta 144 (2015) 252–257
possess the characteristic of natural enzymes, so they exhibit favorable catalytic activity for many chemical reactions. A chitosan– nickel modified carbon paste electrode was rendered to be a capable electrode for electrooxidation of formaldehyde [36]. Zhao and co-workers reported a chitosan–copper complex modified electrode to detect hydrogen peroxide [37]. Yu and co-workers established a nonenzymatic sensor based on chitosan–copper complexes modified multi-walled carbon nanotubes ionic liquid electrode to measure H2O2 [38]. But so far, electrochemical sensors for paracetamol detection based on chitosan–copper complexes or chitosan–nickel complexes have not been reported. Herein, we reported a novel electrochemical sensor based on multi-walled carbon nanotubes (MWCNTs) and chitosan–copper complexes (CTS–Cu) for sensitive determination of paracetamol. The MWCNTs/CTS–Cu modified glassy carbon electrode (GCE) was fabricated by self-assembly technique. Effective parameters on response of the proposed sensor were investigated in details. Finally, the sensor was used for determination of paracetamol in tablet and human serum samples.
2. Experiments 2.1. Meterials and instrumentations Multi-walled carbon nanotubes (MWCNTs) were obtained from Nanjing Jicang Nano Technology Co., Ltd (China). Paracetamol, chitosan(CTS) and CuCl2 2H2O were purchased from Aladdin reagent Co., Ltd. (China). All other reagents were of analytical grade and used without further purification. Ultra-pure water (resistivity no less than 18 MΩ cm) was used for preparation of buffer and standard solutions. A stock solution of 0.1 mol L 1 paracetamol was prepared by diluting paracetamol in 25% ethanol solution. Test standard solutions were prepared daily by appropriate dilution of the stock solution. 0.2 mol L 1 phosphate buffer solutions (PBS) with different pH values were prepared by mixing stock standard solutions of Na2HPO4 and NaH2PO4. All electrochemical studies were performed with a CHI 660B electrochemical workstation (Shanghai Chenhua Instrument Company, China). A conventional three-electrode system was used, consisting of a saturated calomel electrode (SCE) as reference electrode, a platinum foil electrode as counter electrode, and a bare or modified glassy carbon electrode (diameter 3 mm) as working electrode. A magnetic stirrer and a stirring bar provided the convective transport during the amperometric studies. A 0.2 mol L 1 phosphate buffer solution (pH 7.0) was used as supporting electrolyte. All experiments were carried out at room temperature (25 °C). The morphology of different modified electrodes was characterized by a S4800 field-emission scanning electron microscope (Hitachi company, Japan). 2.2. Purification of MWCNTs The MWCNTs were purified according to literature [23]. Firstly, the MWCNTs were heated in air at 600 °C for 2 h, and then soaked in 6 mol L 1 HCl solution for 24 h and centrifuged. The precipitate was rinsed with ultra-pure water and dried under air. Secondly, the MWCNTs were chemically functionalized by ultrasonic agitation in a mixture of sulfuric and nitric acid (3:1) for 8 h. Subsequently, the MWCNTs were filtered, washed with ultra-pure water until pH 7.0 was reached, and then dried at 120 °C for 5 h. Then the multi-walled carbon nanotube functionalized with carboxyl group was obtained.
253
2.3. Preparation of modified electrode A glassy carbon electrode (GCE, diameter 3 mm) was polished to a mirrorlike surface with 1.0, 0.3 and 0.05 μm alumina slurry on silk, respectively. Subsequently, the electrode was rinsed with 1:1 HNO3–H2O (V/V), ethanol and double distilled water in an ultrasonic bath for 2–3 min each wash and air-dried at room temperature [37]. 100 mg MWCNTs were dispersed in 50 mL ultrapure water, and then the mixture was sonicated for 15 min until a black suspension was formed. Chitosan solution was prepared by dissolving 0.25 g chitosan solid in 50 mL 0.10 mol L 1 acetic acid. A copper solution was prepared by dissolving 0.1 g CuCl2 2H2O in 100 mL ultrapure water. The MWCNTs/CTS–Cu modified GCE was fabricated according to the following procedure. Firstly, the MWCNTs modified electrode(MWCNTs/GCE) was prepared by coating the surface of GCE with 5 μL MWCNTs suspension, and then air-dried at room temperature. Secondly, the MWCNTs/GCE was dipped into the chitosan solution for 30 min, and the positive charged chitosan was self-assembled onto the negatively charged MWCNTs functionalized with carboxyl group through the electrostatic interactions. The MWCNTs/CTS/GCE was taken out and rinsed with ultra-pure water. Finally, the MWCNTs/CTS/GCE was dipped into the copper solution for 30 min, and the Cu2 þ was self-assembled onto the chitosan through the complexing actions. The proposed MWCNTs/ CTS–Cu /GCE was taken out, rinsed with ultra-pure water, and then air-dried at room temperature before measurement. The schematic illustration of the process for preparation of MWCNTs/ CTS–Cu/GCE was showed in Fig. 1. 2.4. Analytical procedure Paracetamol was successfully added into an electrochemical cell containing 50 mL 0.2 mol L 1 PBS (pH 7.0) as supporting electrolyte. The electrochemical behaviors of paracetamol on different modified electrodes were studied by cyclic voltammetry (CV), and the concentrations of paracetamol were quantitatively analyzed by differential pulse voltammetry (DPV). The DPV curves were recorded in the potential range from 0.0 V to 0.6 V, with scan rate of 0.1 V s 1, amplitude of 0.05 V, pulse width of 0.05 s and quiet time of 2 s. All measurements were performed at room temperature. During preconditioning, the solution was efficiently stirred.
3. Results and discussion 3.1. Characterization of MWCNTs/CTS–Cu/GCE SEM technique was utilized to characterize the surface morphologies of the fabricated sensors. The SEM image of MWCNTs/GCE (Fig. 2A) displayed a typical morphology of the MWCNTs. From the SEM image of MWCNTs/CTS–Cu/GCE (Fig. 2B), we can obviously see the morphology of the chitosan film except the typical morphology of MWCNTs. The results indicated that the MWCNTs/CTS–Cu complexes were successfully prepared and modified onto the surface of GCE. The MWCNTs/CTS–Cu composites formed a compact film covering the surface of GCE, which increased the specific surface area of the electrode and was conducive to the adsorption of paracetamol. 3.2. Electrochemical behavior of paracetamol on MWCNTs/ CTS–Cu/ GCE Cyclic voltammograms were used to investigate the electrochemical behavior of paracetamol on bare GCE, MWCNTs/GCE and
254
A. Mao et al. / Talanta 144 (2015) 252–257
Fig. 1. Schematic illustration of the process for preparation of MWCNTs/CTS–Cu/GCE.
MWCNTs/CTS–Cu/GCE. Only one oxidation peak was observed in Fig. 3a, indicating that paracetamol demonstrated an irreversible redox behavior on the bare GCE. In contrast, a pair of well-defined redox peaks were obtained in Fig. 3b and c. The results suggested that paracetamol displayed a quasi-reversible redox behavior on the MWCNTs/GCE and MWCNTs/CTS–Cu/GCE. Moreover, the oxidation peak potential significantly shifted to the negative direction, and the oxidation peak current obtained on the MWCNTs/ CTS–Cu/GCE was nearly seven times larger than that obtained on the bare GCE. This was because the MWCNTs and chitosan–copper complexes promoted the electron transfer between paracetamol and the modified electrode, and showed attractive electrocatalytic properties for paracetamol [33–35]. On the other hand, the chitosan could improve the dispersion performance of MWCNTs. Hence, the proposed MWCNTs/CTS–Cu/GCE was selected for further studies on paracetamol detection. 3.3. Effect of scan rate The effect of scan rates on the redox peak currents was investigated in the range of 10–400 mV s 1. Fig. 4 showed the cyclic
voltammograms of paracetamol on the MWCNTs/CTS–Cu/GCE at different scan rates. The results indicated that the redox peak currents increased with the increase of scan rate increasing from 10 to 400 mV s 1. Inset of Fig. 4 showed that both the oxidation and reduction peak currents were linearly proportional to the scan rates in the range of 10–400 mV s 1. The linear regression equations are Ipa (μA)¼(4.168 70.200) þ(0.16270.008)ν(mV s 1) (R¼ 0.999) and Ipc (μA)¼( 0.13370.006) þ (0.1017 0.005) ν(mV s 1) (R¼ 0.997), indicating that the electrochemical reaction of paracetamol on the modified electrode was a surface-controlled process [23]. 3.4. Effect of pH value The effect of pH value on the anodic peak currents of the MWCNTs/CTS–Cu/GCE was studied in the pH range of 5.7–8.0. As shown in Fig. 5, the peak potentials shifted negatively with the pH value increasing from 5.7 to 8.0, which indicated that the redox reaction involved the protons [21]. The anodic peak currents increased with the pH value increasing from 5.7 to 7.0, and then decreased with the pH value increasing from 7.0 to 8.0, suggesting
Fig. 2. SEM images of MWCNTs/GCE (A) and MWCNTs/CTS–Cu/GCE (B).
A. Mao et al. / Talanta 144 (2015) 252–257
Fig. 3. Cyclic voltammograms 1.0 10 5 mol L 1 paracetamol on bare GCE (a), MWCNTs/GCE (b) and MWCNTs/CTS–Cu/GCE (c) in 0.2 mol L 1 phosphate buffer solution (pH 7.0) as supporting electrolyte at a scan rate of 0.1 V s 1.
255
Fig. 5. Cyclic voltammograms of 1.0 10 5 mol L 1 paracetamol on the MWCNTs/ CTS–Cu/GCE in the pH range of 5.7 to 8.0 (from right to left) at a scan rate of 0.1 V s 1. Inset is the plot of the anodic peak potential against pH.
3.5. Effect of deposition potential and deposition time
Fig. 4. Cyclic voltammograms of 1.0 10 5 mol L 1 paracetamol on the MWCNTs/ CTS–Cu/GCE at different scan rates of 10, 25, 50, 75, 100, 125, 150, 175, 200, 250, 300 and 400 mV s 1 (from inner to outer) in 0.2 mol L 1 phosphate buffer solution (pH 7.0) as supporting electrolyte. Inset is the plot of the peak currents vs. scan rates.
that the oxidation reaction of paracetamol was kinetically less favorable at higher pH [15]. But paracetamol was hydrolyzed to p-aminophenol at very low pH values [27].The maximum peak current was obtained at pH 7.0. Hence, the 0.2 mol L 1 PBS (pH 7.0) was chosen as supporting electrolyte in the subsequent experiments. Inset of Fig. 5 showed that the anodic peak potentials of paracetamol were proportional to the pH. Linear regression equation was obtained as Epa (V) ¼0.8091–0.0628 pH (R ¼0.999). According to the slope (0.0628) and the formula Ep ¼K (0.057)m/ npH, m/n was figured out as 1. Furthermore, the redox potential difference (ΔEp) was 0.32 mV. So the electron transfer number was figured out as 2 according to the formula n ¼58/ΔEp. In conclusion, the reaction of paracetamol on the MWCNTs/CTS–Cu/ GCE was a two-electron and two-proton quasi-reversible process. The anodic peak at 0.367 V was ascribed to the oxidation of paracetamol to form N-acetyl-p-quinone imine, and the reduction peak reduction at 0.325 V was ascribed to the reduction of paracetamol to form N-acetyl-p-quinone imine. The possible reaction equation was described as follows:
With the purpose of improving sensitivity, the effect of the deposition potential and deposition time on the response of paracetamol on the MWCNTs/CTS–Cu/GCE was investigated during preconditioning process (see Fig. 6). The influence of the deposition potential on the anodic peak currents of 1.0 10 5 mol L 1 paracetamol was investigated when the deposition time was fixed for 60 s. When the deposition potential shifted negatively from 0.0 to 0.6 V, the anodic peak currents increased. When more negative potentials were applied, the peak currents were essentially unchanged. Therefore, a deposition potential of 0.6 V was chosen for further experiments.The influence of the deposition time on the anodic peak currents of 1.0 10 5 mol L 1 paracetamol was investigated at a fixed deposition potential of 0.6 V. Deposition time was the most important factor for determination of the detection limit in voltammetric analysis. When the deposition time varied in the range of 30–180 s, the peak current increased with the increase of deposition time. When the deposition time increased from 180 s to 240 s, the peak current remained increased slightly. This was because at the same deposition potential, a longer deposition time would make paracetamol be reduced more completely. Subsequently, it would lead to a higher peak current. However, when the deposition time was extremely long, the reduced paracetamol covered the entire effective electrode surface, and the peak current did not change. Therefore, a deposition time of 180 s was chosen for further experiments. 3.6. Analytical characterization Under the optimal experimental conditions, the successive determination of paracetamol on the MWCNTs/CTS–Cu/GCE was carried out in 0.2 mol L 1 phosphate buffer solution by differential
256
A. Mao et al. / Talanta 144 (2015) 252–257
pulse voltammetry (DPV). Fig. 7 showed the DPVs of various concentration of paracetamol ranging from 0.1 to 200 μmol L 1. It could be seen that the anodic peak currents increased with the increase of the concentration of paracetamol, and the anodic peak current (Ip) was linear with the concentration of paracetamol. The calibration plot of the DPV peak current vs. the concentration of paracetamol was shown in the inset of Fig. 6. When the concentration of paracetamol were in the range of 0.1 to 200 μmol L 1, the linear regression equation was Ip (μA)¼ 0.377þ 0.603c (μmol L 1) (R ¼0.999). The detection limit was found to be 0.024 μmol L 1, and the sensitivity was 0.603 A/mol L 1 on signal-to-noise of 3. The comparison of MWCNTs/CTS–Cu/GCE with other modified electrodes for paracetamol detection was listed in Table 1. It can be seen that the MWCNTs/CTS–Cu/GCE offered the widest linear range among the previous methods. Moreover, the detection limit was lower than most of previous reports. The results indicate that the proposed MWCNTs/CTS–Cu/GCE is reliable for the detection of paracetamol. Paracetamol generally suffers from the interference of ascorbic acid (AA) and dopamine (DA) in biological samples [21]. Hence, a systematic study of interference of ascorbic acid and dopamine was carried out to evaluate the selectivity of the proposed sensor. Fig. 8 was the differential pulse voltammogram of AA, DA and paracetamol with equal concentration in a mixture on the MWCNTs/CTS–Cu/GCE, indicating that paracetamol exhibited well-defined DPV wave with good separation from equal concentration AA and DA. The further results showed that 100-fold of Table 1 Comparison of different modified electrodes for paracetamol detection. Electrodes
Methods Linear range Detection lim(nM) it (nM)
References
Poly(L-glutamic)/GCE
DPV
30
[14]
92
[23]
1.0 113
[26] [27]
97 0.09 24
[28] [29] This work
(MWCNTs/NHCH2)6/GCE DPV CoNPs/MWCNTs/GCE MWCNTs/GNS/ GCE
SWV DPV
MWCNTs/polyhis/ GCE MWCNTs/GCE MWCNTs/CTS–Cu/GCE
DPV DPV DPV
100– 140,000 1000– 200,000 5.2–450 480– 215,000 250–5000 0.2–15,000 100– 200,000
Table 2 Determination of paracetamol in tablet samples (n¼ 6). Sample
Labeled (mg/ tablet)
Tablet 1 160 Tablet 2 250 Tablet 3 500
Found (mg/ tablet)
Recovery (%) RSD (%) HPLC (mg)
159.1 248.5 495.8
99.40 98.40 99.20
3.02 2.10 1.86
160.7 251.1 501.9
Table 3 Results of recovery test of paracetamol in human serum samples (n ¼6). Added (μM) 0 10 50 100 a
Not detected.
Found (μM) a
ND 9.99 49.52 98.54
Recovery (%)
RSD (%)
HPLC (μM)
– 99.90 99.04 98.54
– 1.99 2.24 2.62
NDa 10.21 50.46 98.28
ascorbic acid and dopamine did not interfere with the DPV signal of 1.0 μmol L 1 paracetamol (peak current change o 75). Therefore, the sensor could be used to determinate paracetamol in biological samples for its excellent selectivity. A successful sensor primarily requires good reproducibility and stability. The reproducibility of the MWCNTs/CTS–Cu/GCE were investigated by the measurement of the DPV responses to 1.0 10 5 mol L 1 paracetamol. The results showed that the relative standard deviation (RSD) of the anodic peak currents by six successive measurements was 1.84%. The fabrication reproducibility was estimated on five different modified electrodes which were fabricated independently under the same conditions, and the RSD was found to be 3.46%. The above results revealed good reproducibility and stability of the MWCNTs/CTS–Cu/GCE. In addition, the peak current of paracetamol on the MWCNTs/CTS–Cu/ GCE retained 92% of its initial value after the storage of one week in a refrigerator at 4 °C when not in use, and then became 84% of its initial value after the storage of one month. The results suggested that the MWCNTs/CTS–Cu/GCE possessed an acceptable storage stability. 3.7. Recovery test and analytical results of real samples The proposed method was applied to determinate paracetamol in tablet and human serum samples and verify its potential application. To evaluate the applicability of the proposed sensor, the recovery of paracetamol was carried out in the spiked samples of tablet and human serum. The human serum samples were collected from nearby hospital. The serum sample was centrifuged before the determination. The spiked sample was composed of 1% human serum and known amounts of paracetamol in 0.2 M PBS. The results (see Tables 2 and 3) indicated that the recovery of paracetamol on the MWCNTs/CTS–Cu/GCE was satisfactory. Moreover, the detection values of paracetamol were in a good accordance with those obtained by HPLC method.
4. Conclusion In this work, we have developed a new modified glassy carbon electrode based on MWCNTs/CTS–Cu complexes for paracetamol determination. The proposed sensor showed an excellent selectivity for paracetamol in the presence of common potential interfering substances such as ascorbic acid and dopamine, with a wide linear range and high sensitivity. Moreover, the results revealed a good reproducibility and stability of the MWCNTs/CTS– Cu/GCE. With the above excellent performance, the proposed electrode could be used for efficient determination of paracetamol in tablet and human serum samples.
Acknowledgments The authors gratefully acknowledge the financial support from National Natural Science Foundation of China (21275124 and 21305123), National Natural Science Foundation of Jiangsu Province (BK2012247) and Foundation of Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province (AE201162).
References [1] M. Mazer, J. Perrone, Acetaminophen-induced nephrotoxicity: pathophysiology, clinical manifestations, and management, J. Med. Toxicol. 4 (2008) 2–6. [2] M.T. Olaleye, B.T.J. Rocha, Acetaminophen-induced liver damage in mice:
A. Mao et al. / Talanta 144 (2015) 252–257
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19] [20]
[21]
effects of some medicinal plants on the oxidative defense system, Exp. Toxicol. Pathol. 59 (2008) 319–327. A. Goyal, S. Jain, Simultaneous estimation of paracetamol, chlorzoxazone and diclofenac sodium in pharmaceutical formulation by a novel HPLC method, Acta Pharm. Sci. 49 (2007) 147–151. K. Sirajuddin, R. Abdul, A. Shah, M.I. Bhanger, A. Niaz, S. Mahesar, Simpler spectrophotometric assay of paracetamol in tablets and urine samples, Spectrochim. Acta A 68 (2007) 747–751. M.E. Capella-Peiró, D. Bose, M.F. Rubert, J. Esteve-Romero, Optimization of a capillary zone electrophoresis method by using a central composite factorial design for the determination of codeine and paracetamol in pharmaceuticals, J. Chromatogr. B 839 (2006) 95–101. D.L. Oldair, Determination of paracetamol using a flow injection analysis with multi commutation and chemiluminescence detection, Quim. Nova 32 (2009) 1755–1759. C.S. Wesley, P.F. Pereira, M.C. Marra, A simple strategy for simultaneous determination of paracetamol and caffeine using flow injection analysis with multiple pulse amperometric detection, Electroanalysis 23 (2011) 2764–2770. J. Luo, J.J. Cong, R.X. Fang, X.M. Fei, X.Y. Liu, One-pot synthesis of a graphene oxide coated with an imprinted sol–gel for use in electrochemical sensing of paracetamol, Microchim. Acta 181 (2014) 1257–1266. G.C. Yang, L. Wang, J.B. Jia, D.F. Zhou, D.F. Li, Chemically modified glassy carbon electrode for electrochemical sensing paracetamol in acidic solution, J. Solid State Electrochem. 16 (2012) 2967–2977. A. Babaei, B. Khalilzadeh, M. Afrasiabi, A new sensor for the simultaneous determination of paracetamol and mefenamic acid in a pharmaceutical preparation and biological samples using copper(II) doped zeolite modified carbon paste electrode, J. Appl. Electrochem. 40 (2010) 1537–1543. H.S. Yin, K. Shang, X.M. Meng, S.Y. Ai, Voltammetric sensing of paracetamol, dopamine and 4-aminophenol at a glassy carbon electrode coated with gold nanoparticles and an organophillic layered double hydroxide, Microchim. Acta 175 (2011) 39–46. A.R. Khaskheli, J. Fischer, J. Barek, V. Vyskočil, Sirajuddin, M.I. Bhanger, Differential pulse voltammetric determination of paracetamol in tablet and urine samples at a micro-crystalline natural graphite-polystyrene composite film modified electrode, Electrochim. Acta 101 (2013) 238–242. Y. Fan, J.H. Liu, H.T. Lu, Q. Zhang, Electrochemical behavior and voltammetric determination of paracetamol on Nafion/TiO2-graphene modified glassy carbon electrode, Colloid Surf. B 85 (2011) 289–292. Y. Zhang, L.Q. Luo, Y.P. Ding, X. Liu, Z.Y. Qian, A highly sensitive method for determination of paracetamol by adsorptive stripping voltammetry using a carbon paste electrode modified with nanogold and glutamic acid, Microchim. Acta 171 (2010) 133–138. H. Ghadimi, R.M.A. Tehrani, A.S.M. Ali, N. Mohamed, S.A. Ghani, Sensitive voltammetric determination of paracetamol by poly(4-vinylpyridine)/multiwalled carbon nanotubes modified glassy carbon electrode, Anal. Chim. Acta 765 (2013) 70–76. S.S. Nair, S.A. John, T. Sagara, Simultaneous determination of paracetamol and ascorbic acid using tetraoctylammonium bromide capped gold nanoparticles immobilized on 1,6-hexanedithiol modified Au electrode, Electrochim. Acta 54 (2009) 6837–6843. D. Vairavapandian, P. Vichchulada, M.D. Lay, Preparation and modification of carbon nanotubes: Review of recent advances and applications in catalysis and sensing, Anal. Chim. Acta 626 (2008) 119–129. A. Merkoci, M. Pumera, X. Llopis, B. Perez, M. del Valle, S. Alegret, New materials for electrochemical sensing. VI: carbon nanotubes, Trends Anal. Chem., 24, (2005) 826–838. S. Iijima, Helical microtubules of graphitic carbon, Nature 354 (1991) 56–58. X.M. Ren, C.L. Chen, M. Nagatsub, X.K. Wang, Carbon nanotubes as adsorbents in environmental pollution management: a review, Chem. Eng. J. 170 (2011) 395–410. J.M. Hui, W.J. Li, Y.L. Guo, Z. Yang, Y.X. Wang, C. Yu, Electrochemical sensor for
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30] [31] [32]
[33]
[34]
[35] [36]
[37]
[38]
257
sensitive detection of paracetamol based on novel multi-walled carbon nanotubes-derived organic–inorganic material, Biosyst. Eng. 37 (2014) 461–468. R.N. Goyal, V.K. Gupta, S. Chatterjee, Voltammetric biosensors for the determination of paracetamol at carbon nanotube modified pyrolytic graphite electrode, Sens. Actuators B 149 (2010) 252–258. Y.C. Li, S.Q. Feng, S.X. Li, Y.Y. Zhang, Y.M. Zhong, A high effect polymer-free covalent layer by layer self-assemble carboxylated MWCNTs films modified GCE for the detection of paracetamol, Sens. Actuators B 190 (2014) 999–1005. A. Babaei, M. Sohrabi, A.R. Taheri, Highly sensitive simultaneous determination of L-dopa and paracetamol using a glassy carbon electrode modified with a composite of nickel hydroxide nanoparticles/multi-walled carbon nanotubes, J. Electroanal. Chem. 698 (2013) 45–51. T.C. Canevari, P.A. Raymundo-Pereira, R. Landers, E.V. Benvenutti, S.A. S. Machado, Sol–gel thin-film based mesoporous silica and carbon nanotubes for the determination of dopamine, uricacid and paracetamol in urine, Talanta 116 (2013) 726–735. A. Kutluay, M. Aslanoglu, An electrochemical sensor prepared by sonochemical one-pot synthesis of multi-walled carbon nanotube-supported cobalt nanoparticles for the simultaneous determination of paracetamol and dopamine, Anal. Chim. Acta 839 (2014) 59–66. M. Arvand, T.M. Gholizadeh, Simultaneous voltammetric determination of tyrosine and paracetamol using a carbon nanotube-graphene nanosheet nanocomposite modified electrode inhuman blood serum and pharmaceuticals, Colloid, Surf. B 103 (2013) 84–93. P.R. Dalmasso, M.L. Pedano, G.A. Rivas, Electrochemical determination of ascorbic acid and paracetamol in pharmaceutical formulations using a glassy carbon electrode modified with multi-wall carbon nanotubes dispersed in polyhistidine, Sens. Actuators B 173 (2012) 732–736. A. Kutluay, M. Aslanoglu, Modification of electrodes using conductive porous layers to confer selectivity for the voltammetric detection of paracetamol in the presence of ascorbic acid, dopamine and uric acid, Sens. Actuators B 185 (2013) 398–404. H.H.M. Barikani, Applications of biopolymers I: chitosan, Monatsh. Chem. 140 (2009) 1403–1420. Q.P. Song, Z. Zhang, J.G. Gao, Synthesis and property studies of N-carboxymethyl chitosan, J. Appl. Polym. Sci. 119 (2011) 3283–3285. F. Godoy Delolo, C. Rodrigues, M. Martins, A new electrochemical sensor containing a film of chitosan-supported ruthenium: detection and quantification of sildenafil citrate and acetaminophen, J. Braz. Chem. Soc. 25 (2014) 550–552. S. Kianipour, A. Asghari, Room temperature ionic liquid/multiwalled carbon nanotube/chitosan-modified glassy carbon electrode as a sensor for simultaneous determination of ascorbic acid, uric acid, acetaminophen, and mefenamic acid, IEEE Sens. J. 13 (2013) 2690–2698. A. Babaei, M. Afrasiabi, M. Babazadeh, A glassy carbon electrode modified with multiwalled carbon nanotube/chitosan composite as a new sensor for simultaneous determination of acetaminophen and mefenamic acid in pharmaceutical preparations and biological samples, Electroanalysis 22 (2010) 1743–1749. E. Guibal, Heterogeneous catalysis on chitosan-based materials: a review, Prog. Polym. Sci. 30 (2005) 71–109. S.K.H. Darzi, A novel, effective and low cost catalyst for formaldehyde electrooxidation based on nickel ions dispersed onto chitosan-modified carbon paste electrode for fuel cell, J. Electroceram. 33 (2014) 252–263. X.J. Zhao, Z. Dai, X.Y. Zou, Investigation on electrocatalytic performance of chitosan-copper complex modified electrode to hydrogen peroxide, J. Instrum. Anal. 30 (2011) 425–429. Q. Yu, Z.H. Shi, X.Y. Liu, S.L. Luo, W.Z. Wei, A nonenzymatic hydrogen peroxide sensor based on chitosan-copper complexes modified multi-wall carbon nanotubes ionic liquid electrode, J. Electroanal. Chem. 655 (2011) 92–95.