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Original article
11 (
2
); 149-158
doi:
10.1016/j.arabjc.2014.10.009

Fabrication of poly (Solid Red A) modified carbon nano tube paste electrode and its application for simultaneous determination of epinephrine, uric acid and ascorbic acid

, , ,
a School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
b Department of Chemistry, FMKMCC, Madikeri, Constituent College of Mangalore University, Karnataka, India

⁎Corresponding author at: School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. Tel.: +60 0129107573; fax: +60 389213777. manju1853@gmail.com (J.G. Manjunatha)

Received: , Accepted: ,
© The Author(s) 2014
Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

In this study, a stable electroactive thin film of poly(Solid Red A) has been deposited on the surface of a carbon nano tube paste electrode by cyclic voltammetric technique in an pH 7 phosphate buffer solution (PBS) containing Solid Red A. A higher catalytic activity was obtained for electrocatalytic oxidation of ascorbic acid (AA), epinephrine (EP), and uric acid (UA) in pH 7 PBS at over oxidized poly (Solid Red A) film modified carbon nano tube paste electrode (PSRA/MCNTPE) due to an enhanced peak current and well-defined peak separations compared with both bare carbon nano tube paste electrode (BCNTPE) and PSRA/MCNTPE. The electrode surfaces were characterized by field emission scanning electron microscopy (FESEM). Individual and simultaneous determination of AA, EP, and UA were carried out by cyclic voltammetry and differential pulse voltammetry. The reduction peak current was proportional to the EP and UA concentrations in the range of 2.0 × 10−6–9.0 × 10−6 M and 7.0 × 10−6–2 × 10−5 M, respectively. The modified electrode showed good sensitivity, selectivity, stability, and was employed for the determination of EP and UA in real samples.

Keywords

Carbon nanotubes paste electrode
Cyclic voltammetry
Poly(Solid Red A)
Epinephrine
Uric acid
Ascorbic acid
1

1 Introduction

The development of voltammetric sensors for the determination of EP, UA and AA has received significant attention throughout the previous couple of years. The importance of EP within the body is well known and documented (Banks, 2001; Chen and Peng, 2003). It belongs to the cluster of substances known as catecholamine neurotransmitters which include norepinephrine and dopamine (Chen and Peng, 2003). They are mainly necessary for message transfer in the mammalian central nervous system. Changes in the concentration of EP in the body can result in several diseases, therefore its detection and quantification in physiological pH conditions is of great interest. The determination of EP has been reported using chromatographic ways (Shelkovnikov and Gonick, 2004), spectroscopic methods (Efremov et al., 2008), chemiluminescence (Su et al., 2005), capillary electrophoresis (Wei et al., 2005), flow injection analysis (Du et al., 2003), and various electrochemical methods (Ozoemena et al., 2008; Li et al., 2009; Yogeswaran et al., 2007; Beitollahi et al., 2008; Mazloum-Ardakani et al., 2010; Wang et al., 2004). Electrochemical methods offer a simple, cost effective and fast method of analyzing biologically and environmentally vital molecules. The EP electrooxidation at bare electrodes is joined with problems of slow electron transfer rate and adsorptions of EP on the electrode surfaces leading to passivation (Beitollahi et al., 2008; Wang et al., 2002).

AA is known for its reductive properties and for its use on a broad scale as an antioxidant agent in foods and drinks, it is also important for therapeutic purposes and biological metabolism. Thus, recent advances in the food and pharmaceutical industries and a need for nutritional assessment have necessitated the development of a selective, simple and accurate method to determine AA, and it is present in the mammalian brain in the presence of many neurochemical amines together with EP and UA. AA has been used for the prevention and treatment of diseases (Arrigoni and Tullio, 2002) up to now, to detect EP with high selectivity and sensitivity is still a most useful target of electroanalytical research (Wang et al., 2002, 2004; Beitollahi et al., 2011; Salimi et al., 2004).

UA (2,6,8-trihydroxypurine,) is the primary product of purine metabolism (Kaur and Halliwell, 1990). Physiological UA serum levels range from 41 to 88 mg mL−1 and urinary excretion is typically 250–750 mg per day (Zheng et al., 2001). Its abnormal concentration level in a human body may be the symptoms of several diseases, such as gout, hyperuricemia, and Lesch-Nyhan syndrome. Leukemia, pneumonia, and so on are also associated with enhanced urate levels (Kang and Shiu, 2001; Miland et al., 1995). So it is desirable to have a simple and direct method for monitoring the concentration of UA in biological fluids. UA and EP are coexistent in biological fluids of human, so the simultaneous detection of UA and EP in a mixture is quite attractive to biological and chemical researches. Individual determination of UA or EP has been reported by many researches however, simultaneous determination of them is rarely presented.

Nanomaterials have received nice attention in recent years in numerous fields because of their huge potential. Among them, carbon nanotubes (CNTs) have become the topic of intense investigation since their discovery in 1991 by Iijima (1991). Such considerable interest reflects the unique behavior of CNTs, together with their outstanding electrical, chemical, mechanical and structural properties that make them a very attractive material for a large range of applications (Cravotto et al., 2011; Farma et al., 2013; Ajayan, 1999). The benefits of both single-wall (SW) and multi-wall (MW) CNTs, such as high surface area, smart conductance, favorable electronic properties and electrocatalytic effect make them adequate for the construction of electrochemical sensors and biosensors (Beitollahi et al., 2008; Salinas-Torres et al., 2011; Manjunatha et al., 2014).

Polymer modified electrodes have obtained important attention among the researchers for biosensor applications. Electropolymerization is a good method to prepare Polymer modified electrodes as adjusting electrochemical parameters can control film thickness, permeation and charge transport characteristics (Pariente et al., 1994; Sun et al., 1998; Ni et al., 1999; Chen and Peng, 2003).

Electrochemical techniques give an easy, cost less and fast way of analyzing biologically and environmentally molecules (Beitollahi et al., 2014, 2011a; Raoof et al., 2006; Taleat et al., 2008). However, the main drawback for the voltammetric detection of EP in real samples is the interference of the concomitant compounds, such as ascorbic acid (AA) and uric acids (UA), which usually lead in overlapped voltammetric response due to their very similar oxidation peak potentials (Mohammadi et al., 2013; Mokhtari et al., 2012). Recently, chemically modified electrode surface has been proved to be a successful method to solve this problem, and various materials and techniques have been used (Tajik et al., 2013; Raoof et al., 2007) the modified electrodes have many advantages like good biocompatibility, stability and easiness of the preparation (Raoof et al., 2005; Beitollahi et al., 2011b; Mazloum-Ardakani et al., 2010).

In continuation of our studies concerning the preparation of modified electrodes (Manjunatha et al., 2009a,b,c,d, 2010a, 2011a; Manjunatha et al., 2010b, 2011b; Manjunatha et al., 2012a,b, 2013), in this work, the PSRA/MCNTPE was used for the determination of EP, AA and UA individually and also simultaneously. A carbon nano tube paste electrode (CNTPE) consists of a mixture of multiwall carbon nanotube powder and silicone oil as a binder, which is immiscible with water. The well fabricated PSRA/MCNTPE showed an exceptionally low background current, a wide operating potential window, convenient modification, renewability, miniaturization, and low cost. The electrochemical properties of these modified electrodes and their responses toward the simultaneous determination of EP, AA and UA have been investigated by cyclic voltammetric and differential pulse voltammetric techniques. To our knowledge, there is no report about the voltammetric behaviors and determination of EP at PSRA/MCNTPE.

2

2 Experimental

2.1

2.1 Reagents

Solid Red A, EP, AA, UA, Silicone oil were obtained from Sigma Aldrich Malaysia. Solid Red A was prepared from 25 × 10−4 M stock solution by dissolving in 0.1 M sodium hydroxide solution. EP, AA and UA and other chemicals were of analytical grade and used without further purification. EP was prepared 25 × 10−3 M stock solution by dissolving in 0.1 M perchloric acid solution, AA was prepared 25 × 10−3 M stock solution by dissolving double distilled water and 25 × 10−3 M stock solution of UA by dissolving in 0.1 M sodium hydroxide solution. In all the measurements, the supporting electrolyte used was 7 pH 0.2 M PBS. Spectroscopically pure multiwall carbon nanotubes (diameter 50-–00 nm, 5–10 μm length) were obtained from Nanostructured and Amorphous Material Inc., Texas, USA.

2.2

2.2 Apparatus

Electrochemical measurements were carried out with a model-201 electrochemical analyzer (EA-201 Chemilink system, Mumbai, India) in a conventional three-electrode system. The working electrode was a PSRA/MCNTPE, having the cavity of 3 mm diameter. The counter electrode was a bright platinum wire with saturated calomel electrode (SCE) as reference electrode completing the circuit.

2.3

2.3 Preparation of bare carbon paste electrode

The BCNTPE was prepared by mixing in a mortar multiwall carbon nanotube powder and silicone oil in a ratio of 60.0% w/w carbon nanotube powder to 40.0% w/w silicone oil (Shweta et al., 2012). The paste was then packed into the cavity of a homemade electrode and smoothed out on a weighing paper.

2.4

2.4 Preparation of the PSRA/MCNTPE

The polymer film-modified electrode was fabricated by electrochemical polymerization of Solid Red A by cyclic voltammetry in the potential range −400 to 1400 mV at a sweep rate of 100 mV/s in PBS (pH 7). The monomer concentration was usually 75 μL. After 10 cycles (Fig. 1a), the surface of the electrode was washed with doubly distilled water to remove the physically adsorbed material. This modified electrode was immersed in PBS (pH 7.0) and electrochemical studies were carried out. Poly (Solid Red A) film with different thicknesses was achieved by altering scan cycles during the polymerization process as shown in Fig. 1b.

(a) Continuous cyclic voltammograms for electrochemical polymerization of 75 μL Solid Red A on a CNTPE in PBS (pH 7) at scan rate 100 mV/s. (b) Dependence of the oxidation peak current of 0.2 mM EP on the number of voltammetric scans.
Figure 1 (a) Continuous cyclic voltammograms for electrochemical polymerization of 75 μL Solid Red A on a CNTPE in PBS (pH 7) at scan rate 100 mV/s. (b) Dependence of the oxidation peak current of 0.2 mM EP on the number of voltammetric scans.

3

3 Results and discussion

3.1

3.1 Morphological characterization of BCNTPE and PSRA/MCNTPE

Fig. 2 explains the surface morphology of BCNTPE and PSRA/MCNTPE using Field Emission Scanning Electron Microscope. The surface of BCNTPE (Fig. 2a) was irregularly shaped nano sized tubes of carbon nanotubes. However, the PSRA/MCNTPE (Fig. 2b) has typical uniform arrangement of PSRA molecules on the surface of carbon nanotube paste electrode. This confirms the carbon nanotube paste electrode was coated by PSRA film.

FESEM images of (a) BCNTPE (b) PSRA/MCNTPE.
Figure 2 FESEM images of (a) BCNTPE (b) PSRA/MCNTPE.

3.2

3.2 Stability and reproducibility of PSRA/MCNTPE

The main advantage of using the modified electrode is that the electrode surface can be renewed after every use by extrusion of approximately 0.5 mm carbon nanotube paste from the cavity of the Teflon rod and replacing it with a new paste. Indeed five successive renewing of a Solid Red A resulted in an RSD of 4.71%. The stability of the modified film was evaluated by examining the cyclic voltammetric peak currents after continuously scanning for 50 cycles in PBS (pH 7) (data not shown). The percentage degradation of PSRA/MCNTPE was calculated by the following equation, % degradation = i pn i pl × 100 where ip1 and ipn are the first and nth anodic peak currents respectively and is found to be less than 1.2%, indicating that the modified electrode is stable. The stability of the film was also checked by measuring the current response over a period of 20 days, and it is found that the PSRA/MCNTPE maintains 95% of its initial activity even after 20 days.

3.3

3.3 The nature of cyclic voltammograms

The effects of the thickness of the PSRA/MCNTPE can be adjusted by controlling the cyclic number of voltammetric scans and the concentration of Solid Red A. The current response is maximum up to scan number 10 and decreases thereafter. However, after 10 cycles, PSRA/MCNTPE covers the electrode surface completely, active area does not change significantly thereafter, and any further increase in the scan number will result in the decrease in the redox peak current. Hence, we selected 10 cycles as the optimum scan number for the film formation process in this study. Here the focus was to get maximum peak separation between EP, AA and UA. Voltammograms for AA, UA and EP were recorded separately. The conditions were optimized so as to achieve better sensitivity and best separation between the oxidation peaks of AA, UA and EP. The optimum response in this case also was at 75 μL of the modifier Solid Red A in the matrix of PSRA/MCNTPE. Voltammograms of the blank were recorded in PBS (pH 7) as supporting electrolyte with a scan rate of 100 mV/s at BCNTPE and PSRA/MCNTPE. After optimizing the conditions, five replicates were performed under the same identical conditions to calculate RSD for anodic peak currents. Voltammograms of EP, AA and UA in the same buffer solution were recorded separately.

3.4

3.4 Interaction of PSRA/MCNTPE surface with potassium ferrocyanide

The electrochemical response of K4 [Fe (CN)6] at BCNTPE and PSRA/MCNTPE is shown in Fig. 3 at BCNTPE the voltammogram of K4 [Fe (CN)6] showed poor electrochemical response (solid line) with reversible behavior in 1 M KCl as supporting electrolyte. However, the voltammetric response was apparently improved at PSRA/MCNTPE (dashed line) with increasing current. At BCNTPE the anodic peak potential (Epa) was found to be 232 mV and cathodic peak potential (Epc) 168 mV (vs. SCE). The separation of redox potential peaks (ΔEp) was 64 mV and the ratio of peak currents (Ipa/Ipc) 1.61. At PSRA/MCNTPE, a pair of redox peaks is obtained with increase in both anodic and cathodic peak currents. Epa was found at 225 mV and Epc at 192 mV. The separation of redox potential peaks ΔEp was found to be 33 mV and the Ipa/Ipc was 1.30.

Cyclic voltammograms of 1 mM potassium ferrocyanide at the BCNTPE (solid line) and at the PSRA/MCNTPE (dashed line) in 1 M KCl.
Figure 3 Cyclic voltammograms of 1 mM potassium ferrocyanide at the BCNTPE (solid line) and at the PSRA/MCNTPE (dashed line) in 1 M KCl.

3.5

3.5 Electrochemical response of EP on the PSRA/MCNTPE

One of the objectives of this work was the development of a modified electrode capable of electrochemical oxidation of EP. In order to test the electrochemical activity of PSRA/MCNTPE, the cyclic voltammograms were obtained in the absence and presence of 0.2 mM EP, and the curves are shown in Fig. 4(a). In the absence of EP (curve b), no peak can be observed. When 0.2 mM EP was added (curve a), there was a dramatic enhancement of the anodic current, where as the cathodic current peak was enhanced, which is very characteristic of an electrochemical oxidation process. In the present electrochemical approach, the electrode response was proportional to the oxidation of an electroactive species produced. The mechanism of the reaction has been shown in Scheme 1.

(a) Typical cyclic voltammogram of PSRA/MCNTPE with 0.2 mM EP in pH 7 PBS (curve ‘a’) without 0.2 mM EP in pH 7 PBS blank (curve ‘b’). (b) Cyclic voltammograms of 0.2 mM EP in pH 7 PBS at (a) BCNTPE (solid line), (b) PSRA/MCNTPE (dashed line).
Figure 4 (a) Typical cyclic voltammogram of PSRA/MCNTPE with 0.2 mM EP in pH 7 PBS (curve ‘a’) without 0.2 mM EP in pH 7 PBS blank (curve ‘b’). (b) Cyclic voltammograms of 0.2 mM EP in pH 7 PBS at (a) BCNTPE (solid line), (b) PSRA/MCNTPE (dashed line).
Scheme of oxidation of EP.
Scheme 1 Scheme of oxidation of EP.

Fig. 4(b) explains the cyclic voltammogram of 0.2 mM EP in 0.2 M PBS at pH 7 at BCNTPE and PSRA/MCNTPE at 50 mV s−1 sweep rate. The electrochemical response was observed at BCNTPE (solid line). The oxidation peak potential (Epa) was located at 177 mV and reduction peak potential (Epc) response at 249 mV were observed at BCNTPE. The potential difference (ΔEp) was found to be −72 mV. However the strong improvement and reversible redox peaks current were observed at PSRA/MCNTPE. In PSRA/MCNTPE (dashed line) Epa was located at 136 mV and another reduction peak Epc was found at −263 mV. ΔEp was −127 mV. This is the clear evidence that our electrode has better electrocatalytic activity by exposing large surface area for electrochemical oxidation of EP.

3.6

3.6 Effect of scan rate of EP

The effect of scan rate (v) on the peak current and peak potential of EP was evaluated (Fig. 5(a). The influence of the scan rate on the peak current showed a linear relationship between 50 and 150 mV s−1, which is of typical adsorption controlled process (Gosser, 1993) (Fig. 5(b) and the equation can be expressed as follows: i pa ( μ A ) = - 91.46 - 2.0892 ν ( r 2 = 0.99069 )

(a) Cyclic voltammograms of 0.2 mM EP at the PSRA/MCNTPE in pH 7 PBS at various scan rates. From: 50, 75, 100, 125 and 150 mV/s. (b) Plot of the anodic peak current of EP as a function of the scan rate.
Figure 5 (a) Cyclic voltammograms of 0.2 mM EP at the PSRA/MCNTPE in pH 7 PBS at various scan rates. From: 50, 75, 100, 125 and 150 mV/s. (b) Plot of the anodic peak current of EP as a function of the scan rate.

This indicates that the electrode process was controlled by adsorption rather than diffusion. The peak potential shifted to positive values with increasing scan rates.

3.7

3.7 The influence of pH on the electrochemical parameters, Ipa and Epa of EP

The influence of pH on the electrochemical parameters, Ipa and Epa of EP was investigated using cyclic voltammetry in 0.2 M PBS pH in the range 5.5–8.0. It is clear from Fig. 6(a) that Ipa attains maximum value at pH 7.0. The oxidized MWCNTs are functionalized with carboxylic and hydroxyl groups. These groups get deprotonated at pH 7.0 and attain negative charge. Hence, EP gets attracted toward the MWCNTs and a maximum current was observed as shown in Fig. 6(b).

Cyclic voltammograms obtained at the PSRA/MCNTPE in 0.2 M PBS in pH values, (a) 5 (b) 5.5 (c) 6 (d) 6.5 (e) 7 (f) 7.5 (g) 8 containing 0.2 mM EP (b) Plot of anodic peak current vs. pH (5.0–8.0) of 0.2 mM EP at the PSRA/MCNTPE.
Figure 6 Cyclic voltammograms obtained at the PSRA/MCNTPE in 0.2 M PBS in pH values, (a) 5 (b) 5.5 (c) 6 (d) 6.5 (e) 7 (f) 7.5 (g) 8 containing 0.2 mM EP (b) Plot of anodic peak current vs. pH (5.0–8.0) of 0.2 mM EP at the PSRA/MCNTPE.

3.8

3.8 Calibration plot and limit of detection

In order to develop a voltammetric method for determining the EP and UA, we selected the cyclic voltammetric mode. According to the obtained results, it was possible to apply this technique to the quantitative analysis of EP and UA. The PBS of pH 7.0 was selected as the supporting electrolyte for the quantification as EP and UA gave maximum peak currents at pH 7.0. Electrocatalytic oxidation of EP was carried out by varying its concentration at PSRA/MCNTPE by increasing the concentration of EP from 2.0 × 10−6 to 6 × 10−5 M the electrochemical anodic and cathodic peak currents go on increasing with shifting Epa toward the positive and Epc toward the negative direction slightly. Fig. 7(a) shows that the graph of anodic peak current vs concentration of EP showing two linear relationship ranges 2 × 10−6–9 × 10−6 M and 9 × 10−6–6.4 × 10−5 M with the linear regression equations as ipa(A) = 1.5434 × 10−5 + 0.3369C M/L and ipa(A) = 1.57726 × 10−5 + 0.26174C M/L, respectively. The correlation coefficient for the first linearity was 0.99775 and for the second it was found to be 0.9948. Fig. 7(b) shows that the graph of anodic peak current vs. concentration of UA showing two linearity except the range of 7.0 × 10−6–2.2 × 10−5 M and 2.2 × 10−5–2 × 10−4 M. The linear equation ipa(A) = 1.60689 × 10-5 + 0.20047C (r2 = 0.99217) and ipa(A) = 1.64028 × 10-5 + 0.1628C (r2 = 0.99469). Deviation from linearity was observed for more concentrated solutions, due to the adsorption of EP and UA or its oxidation product on the electrode surface (Beitollahi et al., 2008). Related statistical data of the calibration curves were obtained from five different calibration curves. Limit of detection (LOD) was calculated (Swatz and Krull, 1997) based on the peak current using the following equations shown below. LOD = 3 s / m. where s is the standard deviation of the peak currents of the blank (five replicates), and m is the slope of the calibration curve. LOD values were calculated to be 10 × 10−7 M (EP) and 24 × 10−7 M (UA). Table 1 shows the linear range and detection limit for EP at PSRA/MCNTPE in comparison with some sensors of other research groups.

(a) Calibration plot for the determination of EP at the PSRA/MCNTPE in pH 7 PBS with the scan rate 100 mV/s. (b) Calibration plot for the determination of UA at the PSRA/MCNTPE in pH 7 PBS with the scan rate 100 mV/s.
Figure 7 (a) Calibration plot for the determination of EP at the PSRA/MCNTPE in pH 7 PBS with the scan rate 100 mV/s. (b) Calibration plot for the determination of UA at the PSRA/MCNTPE in pH 7 PBS with the scan rate 100 mV/s.
Table 1 Comparison of poly (Solid Red A) with Comparison of efficiency of some modified electrodes for the determination of EP at different modified electrodes.
Electrode Linear range (μM) Detection limit (μM) Method Refs.
DH-CN/CPE 5.0–20 1.000 DPV Mazloum-Ardakani et al. (2012)
CNT/SSE 2.0–100 2.000 DPV Valentini et al. (2007)
MWCNT/CFE 2.0– 00 3.400 CV Ghica and Christopher (2013)
Ag-doped poly(l-glutamine acid)MGCE 3.0–10 0.800 DPV Hu et al. (2008)
PSRA/MCNTPE 2.0–64 1.000 CV This work

3.9

3.9 Simultaneous determination of EP, AA and UA

AA, EP and UA coexist in extra cellular fluid of the central nervous system. In order to establish a sensitive and selective method for the quantification of AA, EP and UA, the ability of the modified electrode to promote the voltammetric resolution of AA, EP and UA was investigated. The cyclic voltammetric response to a mixture of 1 mM AA, 0.2 mM EP and 0.2 mM UA at BCNTPE and PSRA/MCNTPE in pH 7 PBS is shown in Fig. 8(a). The CV obtained at PSRA/MCNTPE exhibits three well-separated oxidation peaks other than one broad oxidation peak at BCNTPE. The differential pulse voltammetric responses to a mixture of 1 mM AA, 0.02 mM EP, and 0.02 mM UA at PSRA/MCNTPE in pH 7 PBS are shown in Fig. 8(b). Similarly, the indistinguishable peak potentials of AA, EP, and UA did not appear when EP was oxidized on PSRA/MCNTPE. Three peaks can be defined well into the PSRA/MCNTPE at potentials around −80, 155, and 328 mV for AA, EP, and UA, respectively. These separations, 235, 173, and 408 mV between AA and EP, EP and UA, and AA and UA, are large enough to achieve the simultaneous detection of these three compounds in a homogeneous solution. Furthermore, at PSRA/MCNTPE, as high as 1 mM AA did not give high signal compared to low concentration of EP and UA, indicating that the PSRA/MCNTPE may be successfully used for quantitative determination of EP and UA in the presence of excess amount of AA.

(a) Cyclic voltammograms obtained at BCNTPE (curve ‘a’) and PSRA/MCNTPE (curve ‘b’) containing mixture of both 0.2 mM EP, 1 mM AA and 0.2 mM UA in 0.2 M PBS of pH 7. (b) DPVs of mixture of 0.02 mM EP, 1 mM AA and 0.02 mM UA in 0.2 M PBS of pH 7. At PSRA/MCNTPE.
Figure 8 (a) Cyclic voltammograms obtained at BCNTPE (curve ‘a’) and PSRA/MCNTPE (curve ‘b’) containing mixture of both 0.2 mM EP, 1 mM AA and 0.2 mM UA in 0.2 M PBS of pH 7. (b) DPVs of mixture of 0.02 mM EP, 1 mM AA and 0.02 mM UA in 0.2 M PBS of pH 7. At PSRA/MCNTPE.

3.10

3.10 Analytical applications

In order to evaluate the analytical applicability of the proposed method, also it was applied to the determination of epinephrine injection (Harson Laboratory, India). Using the proposed methods described above, the injection of epinephrine hydrochloride was analyzed by applying a calibration plot. In addition, a certain value of the standard solution of EP was added into the corresponding injection for testing recovery and the results are shown in Table 2. It demonstrated a good performance of the PSRA/MCNTPE. Cyclic voltammograms were recorded and the peak currents were measured for EP and UA. Fig. 9 shows a typical cyclic voltammogram for the simultaneous determination of 1:500 dilutions of EP and UA in epinephrine hydrochloride and healthy human urine sample solution respectively. The results were consistent well with the certified values, suggesting that the PSRA/MCNTPE has a good precision and the proposed method can be efficiently applied to the simultaneous determination of EP and UA with satisfactory reproducibility and the recoveries were acceptable, showing that the proposed methods could be efficiently used for the determination of EP in injection samples.

Table 2 Determination of EP in injections (n = 5).
Sample Added (mg mL−1) RSD (%) Recovery (%)
1 31 2.81 102.2
2 39 0.30 99.41
3 47 1.70 101
Typical cyclic voltammogram for the simultaneous determination of EP and UA in EP injection USP and healthy human urine sample solution respectively.
Figure 9 Typical cyclic voltammogram for the simultaneous determination of EP and UA in EP injection USP and healthy human urine sample solution respectively.

4

4 Conclusion

In this paper, the PSRA/MCNTPE was used to investigate the behaviors of EP electrochemically in mixture of solution, at physiological pH, containing AA and UA both by cyclic voltammetry and differential pulse voltammetry techniques. Linear calibration plots for the oxidation of EP and UA were obtained in the range of 2 × 10−6–9.0 × 10−6 M and 7 × 10−6–2.2 × 10−5 M. The linear equation ipa(A) = 1.5434 × 10−5 + 0.3369C and ipa(A) = 1.60689 × 10−5 + 0.20047C for UA with a correlation co-efficient of 0.997 and 0.992, respectively. The modified electrode and the proposed method have been practically and successfully applied for the simultaneous determination of UA and EP in real samples and showed excellent sensitivity, selectivity and anti-fouling properties.

Acknowledgements

We acknowledge grants from the Universiti Kebangsaan Malaysia (UKM-GUP-216-2011, UKM-DLP-2012-022, UKM-DLP-2012-023), and the support of the CRIM (Centre for Research and Innovation Management). The authors also thank Mr Saini Sain for help with laboratory work.

References

  1. , . Nanotubes from carbon. Chem. Rev.. 1999;99:1787-1799.
    [Google Scholar]
  2. , , . Ascorbic acid: more than just an antioxidant. Biochim. Biophys. Acta. 2002;11569:1-9.
    [Google Scholar]
  3. , . Enhanced leptin transport across the blood-brain barrier by α1-adrenergic agents. Brain Res.. 2001;899:209-217.
    [Google Scholar]
  4. , , , , . Novel 2,2′-[1,2-ethanediylbis(nitriloethylidyne)]-bis-hydroquinone double-wall carbon nanotube paste electrode for simultaneous determination of epinephrine, uric acid and folic acid. Biosens. Bioelectron.. 2008;24:362-368.
    [Google Scholar]
  5. , , , . Electroanalysis and simultaneous determination of 6-thioguanine in the presence of uric acid and folic acid using a modified carbon nanotube paste electrode. Anal. Sci.. 2011;27:991-997.
    [Google Scholar]
  6. , , , . Application of a carbon-paste electrode modified with 2,7-Bis(ferrocenyl ethyl)fluoren-9-one and carbon nanotubes for voltammetric determination of levodopa in the presence of uric acid and folic acid. Electroanalysis. 2011;23:1934-1940.
    [Google Scholar]
  7. , , , , . Electrocatalytic determination of captopril using a modified carbon nanotube paste electrode: application to determination of captopril in pharmaceutical and biological samples. Measurement. 2014;47:770-776.
    [Google Scholar]
  8. , , . The electrochemical properties of dopamine, epinephrine, norepinephrine, and their electrocatalytic reactions on cobalt(II) hexacyanoferrate films. J. Electroanal. Chem.. 2003;547:179-189.
    [Google Scholar]
  9. , , , , , , , , . Rapid purification/oxidation of multi-walled carbon nanotubes under 300 kHz-ultrasound and microwave irradiation. New J. Chem.. 2011;35:915-919.
    [Google Scholar]
  10. , , , . Flow injection chemiluminescence determination of epinephrine using epinephrine-imprinted polymer as recognition material. Anal. Chim. Acta. 2003;489:183-189.
    [Google Scholar]
  11. , , , . Achievements in resonance Raman spectroscopy. Anal. Chim. Acta. 2008;606:119-134.
    [Google Scholar]
  12. , , , , , , , , , . Physical and electrochemical properties of supercapacitor electrodes derived from carbon nanotube and biomass carbon. Int. J. Electrochem. Sci.. 2013;8:257-273.
    [Google Scholar]
  13. , , . Brett simple and efficient epinephrine sensor based on carbon nanotube modified carbon film electrodes. Anal. Lett.. 2013;46:1379-1393.
    [Google Scholar]
  14. , . Cyclic Voltammetry: Simulation and Analysis of Reaction Mechanisms. New York: VCH; . p. 43
  15. , , , . Chem. Anal.. 2008;53:703.
  16. , . Helical microtubules of graphitic carbon. Nature. 1991;354:56-58.
    [Google Scholar]
  17. , , . Determination of uric acid at electrochemically activated glassy carbon electrode. Electroanalysis. 2001;13:1319-1325.
    [Google Scholar]
  18. , , . Action of biologically-relevant oxidizing species upon uric acid. Identification of uric acid oxidation products. Chem. Biol. Interact.. 1990;73:235-247.
    [Google Scholar]
  19. , , , . Multiwalled carbon nanotubes with poly(NDGAChi) biocomposite film for the electrocatalysis of epinephrine and norepinephrine. Anal. Biochem.. 2009;388:288-295.
    [Google Scholar]
  20. , , , , , , . Cyclic voltammetric studies of dopamine at lamotrigine and TX-100 modified carbon paste electrode. Int. J. Electrochem. Sci.. 2009;4:187-196.
    [Google Scholar]
  21. , , , , , , , , . Electrochemical studies of dopamine at eperisone and cetyl trimethyl ammonium bromide surfactant modified carbon paste electrode: a cyclic voltammetric study. Int. J. Electrochem. Sci.. 2009;4:662-671.
    [Google Scholar]
  22. , , , , , , , . Electrochemical response of dopamine at phthalic acid and Triton X-100 modified carbon paste electrode: a cyclic voltammetry study. Int. J. Electrochem. Sci.. 2009;4:1469-1478.
    [Google Scholar]
  23. , , , , , , . Electrocatalytic response of dopamine at mannitol and Triton X-100 modified carbon paste electrode: a cyclic voltammetric study. Int. J. Electrochem. Sci.. 2009;4:1706-1718.
    [Google Scholar]
  24. , , , , , . Sensitive voltammetric determination of dopamine at salicylic acid and TX-100, SDS, CTAB modified carbon paste electrode. Int. J. Electrochem. Sci.. 2010;5:682-695.
    [Google Scholar]
  25. , , , , , , . Electrochemical studies of dopamine and epinephrine at a poly (tannic acid) modified carbon paste electrode: a cyclic voltammetric study. Int. J. Electrochem. Sci.. 2010;5:1236-1245.
    [Google Scholar]
  26. , , , , , . Poly (maleic acid) modified carbon paste electrode for simultaneous detection of dopamine in the presence of uric acid: a cyclic voltammetric study. Anal. Bioanal. Electrochem.. 2011;3:146-159.
    [Google Scholar]
  27. , , , , , , . Electrochemical studies of clozapine drug using carbon nanotube-SDS modified carbon paste electrode: a cyclic voltammetry study. Der Pharma Chem.. 2011;3:236-249.
    [Google Scholar]
  28. , , , , . Selective determination of dopamine in the presence of ascorbic acid using a poly (nicotinic acid) modified carbon paste electrode. Anal. Bioanal. Electrochem.. 2012;4:225-237.
    [Google Scholar]
  29. , , , , . Simultaneous voltammetric measurement of ascorbic acid and dopamine at poly (vanillin) modified carbon paste electrode: a cyclic voltammetric study. Der Pharma Chem.. 2012;4:2489-2497.
    [Google Scholar]
  30. , , , , . Simultaneous determination of ascorbic acid, dopamine and uric acid at poly (aniline blue) modified carbon paste electrode: a cyclic voltammetric study. Int. J. Pharm. Pharm. Sci.. 2013;5:355-362.
    [Google Scholar]
  31. , , , , , , . Sodium dodecyl sulfate modified carbon nanotubes paste electrode as a novel sensor for the simultaneous determination of dopamine, ascorbic acid, and uric acid. C. R. Chimie. 2014;17:465-476.
    [Google Scholar]
  32. , , , , , , , . Simultaneous determination of epinephrine and acetaminophen concentrations using a novel carbon paste electrode prepared with 2,2′-[1,2 butanediyl bis(nitriloethylidyne)]-bis-hydroquinone and TiO2 nanoparticles. Colloids Surf. B. 2010;76:82-87.
    [Google Scholar]
  33. , , , , , . New strategy for simultaneous and selective voltammetric determination of norepinephrine, acetaminophen and folic acid using ZrO2 nanoparticles-modified carbon paste electrode. Sens. Actuators, B. 2010;151:243-249.
    [Google Scholar]
  34. , , , , , , , , . Carbon nanoparticles and a new derivative of hydroquinone for modification of carbon paste electrode for simultaneous determination of epinephrine and acetaminophen. Anal. Methods. 2012;4:2127-2133.
    [Google Scholar]
  35. , , , , , . Poly(o-aminophenol)-modified bienzyme carbon paste electrode for the detection of uric acid. Talanta. 1995;43:785-796.
    [Google Scholar]
  36. , , , . Electrochemical behaviour of a modified carbon nanotube paste electrode and its application for simultaneous determination of epinephrine, uric acid and folic acid. Sensor Lett.. 2013;11:388-394.
    [Google Scholar]
  37. , , , , . Application of modified multiwall carbon nanotubes paste electrode for simultaneous voltammetric determination of morphine and diclofenac in biological and pharmaceutical samples. Sens. Actuators, B. 2012;169:96-105.
    [Google Scholar]
  38. , , , , . Amperometric determination of epinephrine with an osmium complex and nafion double-layer membrane modified electrode. Anal. Chim. Acta. 1999;378:151-157.
    [Google Scholar]
  39. , , , . Influence of solution pH on the electron transport of the self-assembled nanoarrays of single-walled carbon nanotube-cobalt tetraaminophthalocyanine on gold electrodes: electrocatalytic detection of epinephrine. Electrochim. Acta. 2008;53:2844-2851.
    [Google Scholar]
  40. , , , . Electrocatalysis of NADH oxidation with electropolymerized films of 3,4-dihydroxybenzaldehyde. Anal. Chem.. 1994;66:4337-4344.
    [Google Scholar]
  41. , , , , . Electrocatalytic determination of ascorbic acid at the surface of 2,7-Bis(ferrocenyl ethyl)fluoren-9-one modified carbon paste electrode. Electroanalysis. 2005;18:1193-1201.
    [Google Scholar]
  42. , , , , . Electrocatalytic oxidation and highly selective voltammetric determination of L-cysteine at the surface of a 1-[4-(ferrocenyl ethynyl)phenyl]-1-ethanone modified carbon paste electrode. Anal. Sci.. 2006;22:1213-1220.
    [Google Scholar]
  43. , , , . L-cysteine voltammetry at a carbon paste electrode bulk-modified with ferrocenedicarboxylic acid. Electroanalysis. 2007;19:1822-1830.
    [Google Scholar]
  44. , , , . Abrasive immobilization of carbon nanotubes on a basal plane pyrolytic graphite electrode: application to the detection of epinephrine. Analyst. 2004;129:225-228.
    [Google Scholar]
  45. , , , , . Study on electroactive and electrocatalytic surfaces of single walled carbon nanotubes-modified electrodes. Electrochim. Acta. 2011;56:2464-2470.
    [Google Scholar]
  46. , , . Peroxynitrite but not nitric oxide donors destroys epinephrine: HPLC measurement and rat aorta contractility. Life Sci.. 2004;75:2765-2773.
    [Google Scholar]
  47. , , , . Voltammetric behavior of theophylline and its determination at multiwall carbon nanotube paste electrode. Colloids Surf. B: Biointerfaces. 2012;97:1-6.
    [Google Scholar]
  48. , , , . Determination of epinephrine based on its enhancement for electrochemiluminescence of lucigenin. Talanta. 2005;65(2):531-536.
    [Google Scholar]
  49. , , , , . The electrochemical copolymerization of 3,4-dihydroxybenzoic acid and aniline at microdisk gold electrode and its amperometric determination for ascorbic acid. Talanta. 1998;45:851-856.
    [Google Scholar]
  50. , , . Analytical Method Development and Validation. New York: Marcel Dekker; .
  51. , , , . Simultaneous determination of droxidopa and carbidopa using a carbon nanotubes paste electrode. Sens. Actuators, B. 2013;188:923-930.
    [Google Scholar]
  52. , , , , , , . Electrochemical behavior of ascorbic Acid at a 2,2′-[3,6-Dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone carbon paste electrode. Anal. Sci.. 2008;24:1039-1044.
    [Google Scholar]
  53. , , , , , , . Functionalized single-walled carbon nanotubes modified microsensors for the selective response of epinephrine in the presence of ascorbic acid. Electroanalysis. 2007;19:859-869.
    [Google Scholar]
  54. , , , . Electrochemical behavior of epinephrine at L-cysteine self-assembled monolayers modified gold electrode. Talanta. 2002;57:687-692.
    [Google Scholar]
  55. , , , . Study on the electrochemical behavior of epinephrine at a poly (3-methylthiophene)-modified glassy carbon electrode. Electroanal. Chem.. 2004;570:83-90.
    [Google Scholar]
  56. , , , . Separation and determination of norepinephrine, epinephrine and isoprenaline enantiomers by capillary electrophoresis in pharmaceutical formulation and human serum. J. Chromatogr. A. 2005;1098:166-171.
    [Google Scholar]
  57. , , , . Nanocomposite of functionalized multiwall carbon nanotubes with nafion, nano platinum, and nano gold biosensing film for simultaneous determination of ascorbic acid, epinephrine, and uric acid. Anal. Biochem.. 2007;365:122-131.
    [Google Scholar]
  58. , , , , , . Selective determination of uric acid by using a β-cyclodextrin modified electrode. Electroanalysis. 2001;13:1351-1354.
    [Google Scholar]

Appendix A

Supplementary data

Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.arabjc.2014.10.009.

Appendix A

Supplementary data

Supplementary data

Supplementary data


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