Simultaneous electroanalysis of dopamine, paracetamol and folic acid using TiO2-WO3 nanoparticle modified carbon paste electrode

Journal Pre-proof Simultaneous electroanalysis of dopamine, paracetamol and folic acid using TiO2-WO3 nanoparticle modified carbon paste electrode

N.B. Ashoka, B.E. Kumara Swamy, H. Jayadevappa, S.C. Sharma PII:

S1572-6657(20)30002-3

DOI:

https://doi.org/10.1016/j.jelechem.2020.113819

Reference:

JEAC 113819

To appear in:

Journal of Electroanalytical Chemistry

Received date:

6 July 2019

Revised date:

30 December 2019

Accepted date:

1 January 2020

Please cite this article as: N.B. Ashoka, B.E.K. Swamy, H. Jayadevappa, et al., Simultaneous electroanalysis of dopamine, paracetamol and folic acid using TiO2-WO3 nanoparticle modified carbon paste electrode, Journal of Electroanalytical Chemistry(2020), https://doi.org/10.1016/j.jelechem.2020.113819

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© 2020 Published by Elsevier.

Journal Pre-proof Simultaneous Electroanalysis of Dopamine, Paracetamol and Folic acid using TiO2- WO3 Nanopartical Modified Carbon Paste Electrode N.B Ashokaa, B. E Kumara Swamya*, H. Jayadevappab and S.C. Sharmac+ Department of P. G. Studies and Research in Industrial Chemistry, Kuvempu University, JnanaSahyadri, Shankaraghatta - 577 451, Shimoga, Karnataka, India. b

c

Department of Chemistry, Sahyadri Science College, Shimoga, Karnataka, India.

Director-National Assessment and Accreditation Council (work carried out as Honorary Professor, Jain University, Bangalore 560 069, India).

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Abstract

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In this study, mixed titanium oxide and tungsten trioxide nanoparticles (TiO2-WO3NPs) were prepared and characterized by different characterization techniques. The prepared materials

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TiO2-WO3NPs were used as modifiers in carbon paste electrode (TiO2-WO3NPs/MCPE) to study the electrochemical behaviour of dopamine (DA) in phosphate buffer solution (PBS) at pH 7.4

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by using cyclic voltammetric (CV) technique. The TiO2-WO3NPs/MCPE shows enhanced electrocatalytic activity compared to bare CPE. As a result, the TiO2-WO3NPs/MCPE was used

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for further electrochemical studies. The effect of pH proposed that an equal number of electron and proton are involved in the electrochemical reaction of DA. The DA concentration

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determination was in the range 2×10-6 M to 18×10-6 M and the limit of detection (LOD) and limit of quantification were found to be 10.18nM and 34.32nM. From the scan rate study the

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oxidation of DA was found to be adsorption controlled and simultaneous detection of DA, PA and FA were well separated in CV and differential pulse voltammetric (DPV) technique. Moreover the stability and reproducibility of TiO2-WO3NPs /MCPE at DA was studied and furthermore successfully demonstrated for the detection of DA in blood serum and injection samples. Keywords: Titanium oxide and tungsten trioxide nanoparticles, dopamine, folic acid, paracetamol and modified carbon- paste electrodes. *Corresponding Author: Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Jnana Sahyadri, Shankaraghatta, Shimoga, Karnataka 577451, India, Ph:+91-8282-256225(Off),Fax:+91-8282-256255, 1

Journal Pre-proof Email address:[email protected], [email protected], + S.C.Sharma [email protected] 1. Introduction TiO2-WO3 nanomaterials are transition metal oxides due to which they are highly attractive for various applications encircling electrochromic devices, dye sensitized solar cells, photocatalysis, hydrogen production and sensing applications due to their low cost, non-toxicity, high

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efficiency, chemical inertness and ability to be synthesized in various morphologies.TiO2-WO3

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has increased much attention for researchers because of their excellent chemical and physical

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properties. Most of the studies on TiO2-WO3 have been reported on composite thin films which

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can be used in photoelectrochromic devices, gas sensors, photocatalysis and fuel cells and

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sensors etc. [1-19].

Dopamine (DA) is a significant catecholamine acting as a neurotransmitter in the brain. Its

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essential role includes regulating attention, movement, cognition, pleasure and hormonal

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processes. In addition, it is extensively distributed in the renal, central nervous, cardiovascular

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and hormonal system. A significant reduction of DA has been strongly associated with Schizophrenia, Restless leg syndrome, HIV infection, attention deficit hyperactivity disorder (ADHD) and Parkinson’s disease [20-24]. It is an extremely strong, electrochemically active molecule which gives dopamine-ortho-Quinone (DOQ) as an oxidant product [25]. There are numerous techniques for the detection of DA together with fluorimetry, UV-visible spectroscopy, electrochemical methods, capillary electrophoresis and chemiluminescence. Among these techniques electrochemical method is fast, low cost, high accuracy and low detection limit [26-32]. Paracetamol (N-acetyl-p-aminophenol) renowned as acetaminophen is a non-steroidal, anti-inflammatory drug normally used in the pharmaceutical application for its 2

Journal Pre-proof sturdy, antipyretic and analgesic action. It is also used in managing of postoperative pain [3335]. Generally paracetamol (PC) does not show any destructive side effects but excess dosage causes damage of kidney and liver. This directs to serious nephrotoxicity and hepatotoxicity. PC is one of the most commonly used analgesics in pharmaceutical formulations for the reduction of fever and also as a pain killer for the relief of mild to moderate pain associated with headache, backache, arthritis and postoperative pain in adults and children [36-38]. Folic acid (FA) is also

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known as pteroylglitamic acid which is water soluble Vitamin-B and an important haematogenic

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agent which acts as an co-enzyme to regulate the production of ferrohaeme [39]. Vegemite or

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marmite also encloses folate with an average part (5g) containing 100 µg. In many nutrients, FA

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encompasses huge significance for woman planning for pregnancy. Lack of FA increases devolution of mind, gigantocytic anemia, leucopoenia, neurosis and is considered to increase the

high-performance

liquid

chromatography

(HPLC)

and

flow

injection

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fluorometry,

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chances of heart attack and stroke. At present, some measurements such as spectrophotometry,

chemiluminescence have been used to detect FA [40-43]. Hence the determination of FA is often

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essential for pharmaceutical, clinical and food samples.

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In the present study, the carbon paste electrode (CPE) was modified using prepared TiO2-WO3 nanoparticle. This fabricated modified electrode was used as dopamine biosensor and moreover in the electrochemical studies of paracetamol and folic acid. TiO2-WO3 nanoparticles enhanced the electrocatalytic activity in the determination of DA. The fabricated TiO2-WO3 was used to study the various electrochemical parameters of DA, PC and FA, as well as the simultaneous determination of DA in presence of PC and FA. Moreover the TiO2-WO3 /MCPE are also used for the analysis of DA injection sample and also this modifier is used to detect high stability,

3

Journal Pre-proof reproducibility and repeatability. The various characterization techniques for TiO2-WO3 NPs such as XRD, SEM, EDX and IR were used. 2. Experimental 2.1 Reagents and Apparatus The titanium oxide was purchased from sigma Aldrich and the sodium hydroxide (NaOH),

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ammonium metatungstateand dopamine hydrochloride was from Merck chemicals. Perchloric acid, silicon oil, paracetamol and folic acid from Himedia. These chemicals were used without

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further purification. Paracetamol and phosphate buffer solutions of different pH were prepared

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from double distilled water. The stock solutions dopamine was prepared from 0.1M perchloric

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acid and folic acid from 0.1 M NaOH.

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The structure of prepared TiO2-WO3NPs was studied by XRD using a (Model D8 Advance, Bruker) with a Cu- Kα1 X-ray radiation (λ = 0.15406 nm) diffractometer. The morphological

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structure of the synthetic TiO2, WO3 and TiO2-WO3NPs was studied using an H-

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7600(HITACHI) Transmission electron microscopy (TEM) and VEGA3 TESCAN Scanning electron microscopy (SEM). IR absorption spectra are recorded in IR SPECTRUM 1000

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PERKIN ELMER spectrometer. Cyclic voltammetric experiments were performed using the model CH660c (CH instruments). Electrochemical cell composed of a counter (platinum) and reference (saturated calomel) electrodes and bare or TiO2-WO3NPs/MCPE were used as working electrodes. 2.3 Preparation of TiO2-WO3NPs TiO2-WO3NPs obtained by hydrothermal method, WO3 nanoparticles were prepared by hydrolysis of tungsten carbide, uniformly mixed commercial TiO2 nanoparticles was added at

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Journal Pre-proof room temperature to WO3 solution and thoroughly mixed. The hydrothermal reaction took place in a Teflon autoclave at 150∘C for 25h. Precipitated TiO2-WO3NPs were centrifuged (4000rpm), dried at 100∘C to dry mass, and calcinated at 500–800∘C for 3h. 2.4 Preparation of the bare and MCPEs The bare carbon paste electrode (BCPE) was prepared by homogeneous mixing of graphite

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powder and silicon oil (70:30 w/w) in an agate mortar by grinding about 30min. A part of the carbon paste was packed into the home made cavity and smoothed on a tissue paper. Each

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MCPE were prepared by grinding mass ratio 70:30 of graphite and silicon oil. In addition to

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modifier, 20 mg of TiO2-WO3 nanoparticles were added to above mentioned graphite powder

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and silicon oil mixture.

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3. Results and discussion

3.1 Characterization of prepared TiO2/WO3NPs

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Obtained powder X-ray diffraction (XRD) of the TiO2, WO3 and TiO2-WO3 nanoparticles is

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shown in Fig.1 (A, B and C) respectively.Fig.1A, powder XRD pattern for the commercial TiO2 indexed to tetragonal structure and matched with (ICCD PDF 21-1272) and Fig.1B, WO3 films

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exhibit orthorhombic structure and peaks matched with standard pattern WO3 (JCPDS No. 431035). The XRD patterns of Fig. 1C, TiO2–WO3 nanoparticles containing different proportions of Ti and W. It was found that the products were composed of tetragonal structured TiO2 (JCPDS 21-1272) and orthorhombic-phase WO3 (JCPDS 46-1096). The surface morphology of SEM images clearly show different morphologies and sizes for TiO2, WO3 and TiO2-WO3 are shown in Fig 2 (A, B and C).The SEM images of Fig 2 (A, B and C) shows an spherical morphology and the individual spherical shape were joined together to form clusters. The TEM images of TiO2, WO3 and TiO2-WO3 are shown in Fig 3 (A, B and C) it is established that the 5

Journal Pre-proof presence of particles depicted from the TEM micrographs are well crystalline and spherical shape. Fig 3A shows the average size of the TiO2NPs was about 22 nm. Fig. 3B shows the products prepared by pure WO3 nanoparticles, with an average size of 60 nm. Fig.3C shows the WO3 are uniformly distributed on the TiO2 and TiO2-WO3 images shows agglomerate and average particle size is about 40 nm [44, 45]. EDX analysis images of TiO2, WO3 and TiO2-WO3 are shown in Fig 4A, Fig.4B and Fig.4C. TiO2 confirms that Ti and O are present as shown in

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Fig.4A; WO3 confirms that W and O are present in Fig.4B, whereas TiO2-WO3 shows Ti, W and

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O are present as shown in Fig.4C. There is no impurity in these nanoparticles.

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> Fig.1, Fig.2, Fig.3, Fig.4A Fig.4B and Fig.4C <

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3.2 Electrochemical response of DA at different quantities of modifiers in CPE

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In order to optimize the quantity of TiO2-WO3NPs/MCPE, different quantity of the TiO2WO3NPs in a CPE were used to determine the 2×10-6M of DA in phosphate buffer solution

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(PBS) at pH 7.4 and recorded at the scan rate of 50mVs−1as shown in Fig 5. The plot of anodic

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peak current (Ipa) versus the percentage weight (0.4, 0.6, 0.8, 1.0 and 1.2%) of TiO2-WO3NPs modifiers CPE, The obtained results show an increase in the quantities of modifier in the CPEs,

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the corresponding anodic peak current also increases slightly up to 0.6%

and increases

instantaneously at 0.8% of TiO2-WO3NPs modifiers and further at 1.0% the anodic peak current decreases. As a result 0.8% MCPEs were used as optimized electrodes for the further electrochemical investigations as shown in scheme 1. > Fig.5 and Scheme 1< 3.3 The electrochemical behaviour of DA at the bare CPE and TiO2–WO3NPs/MCPE

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Journal Pre-proof The electrochemical response of 2×10-6M DA at BCPE (dashed line) and TiO2– WO3NPs/MCPE (solid line) sweep rate of 50mVs−1 is as shown in Fig.6. DA is an easily oxidizable electroactive catecholamine which showed poor sensitivity and reproducibility at BCPE in 0.2M PBS at pH 7.4. The TiO2–WO3NPs/MCPE showed good enhancement in the anodic peak current (Ipa) compared to BCPE, among that TiO2–WO3NPs/MCPE illustrated very significant enhancement in the peak current with minimization in over potential

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compared to bare electrode. The differences in peak potential (ΔEp) were found to be at

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0.052V and 0.034V for BCPE and TiO2–WO3NPs/MCPE respectively. The mechanism may

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be due to TiO2–WO3NPs/MCPE combined with the hydrogen bond of the hydroxyl of DA, which activated hydroxyl, weakened the bond energy of O–H and improved the electron transfer

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rate. At the same time, high surface area of the TiO2–WO3NPs/MCPE improved the electrode

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contact area of DA. [46]

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> Fig.6<

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3.4 Effect of pH on the determination of DA at the TiO2–WO3NPs/MCPE

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The pH of the supporting electrolyte has a significant influence on the DA electrocatalysis at the TiO2-WO3NPs/MCPE by affecting peak potential as shown in the Fig 7.The effect of pH value in the determination of DA in PBS solution at TiO2-WO3NPs/MCPE was carefully investigated in a wider pH range of 5.8 to 8.2 of 2×10-6M DA in the different pH solutions. Fig 7 (inset)The formal potential of DA shifts negatively with the increase in the pH value of solution and depends linearly on the pH value in the range of 5.5 to 8.5 with a slope of 0.052 V/pH (R2 = 0.9810). It demonstrates that the redox of DA undergoes a two-electron and two-proton process, which is consistent with that reported in literature [47–52]. > Fig.7< 7

Journal Pre-proof 3.5 Effect of scan rate on DA at the TiO2–WO3NPs/MCPE The scan rate influences the electrochemical investigation of DA and the effect of scan rate of DA (2×10-6M) in presence of PBS (pH 7.4) was studied by CV technique at TiO2WO3NPs/MCPE. Fig. 8 shows the electrochemical response of 2×10-6M DA at TiO2WO3NPs/MCPE at different scan rate (50 to 500 mVs-1), the anodic peak slightly shifts towards

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positive potential and cathodic peak slightly shifts towards the negative potential along with increase in peak current through increasing the scan rate, Fig. 8 (inset) shows the graph of Ipa

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versus square root of scan rate with linear regression : Ipa (µA) = 2.72 × 10-7 + 8.60 ×10-9 ν

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(mV/s) (R2 = 0.9997). Hence this study shows that the electrode reaction was adsorption

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controlled process [53, 54].

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Eq. (1) determining the value of k0 from experimental Ep values was valid approximation of such curves for Ep>10 mV. The values of k° for the DA were determined from the

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experimental ΔEp values, the data are in Table 1. The values of k0 indicate that strong

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adsorptions of reactants and products are involved. Here, the k0 is the heterogeneous rate constant and Ep is the potential difference between the anodic and cathodic peak potentials.

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The heterogeneous rate constant (k0) was estimated using Eq. (1). The value of k0 obtained at the scan rate of 50mVs−1 for the MCPE prepared with TiO2-WO3NPs/MCPE exhibits a larger heterogeneous rate constant compared with those determined in other scan-rate-variation studies. The calculated data are tabulated in Table 1. [46] Ep=201.39 log (/k0)-301.78…………. (1) > Fig.8 and Table-1< 3.6 The Concentration effect of DA at the TiO2–WO3NPs/MCPE

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Journal Pre-proof The electrocatalytic oxidation of DA was carried out by varying its concentration at TiO2WO3NPs/MCPE. Fig 9 shows that with increasing concentration of DA from 2×10-6 M to 18×106

M the anodic and cathodic peak current(Ipa and Ipc) go on increasing with a small shifting in

the oxidation potentials. The graph of Ipa versus the concentration of DA was plotted as shown in Fig. 9 (inset) and it shows almost straight line with good linearity with the linear regression equation Ipa (µA) =2.52(C0 10-8M/L)+ 0.62 (10-6A) (r2=0.9976). The limit of detection (LOD)

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and limit of quantification (LOQ) of TiO2-WO3NPs/MCPE were calculated using the equation

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3S/M and 10S/M, where M is the slope of the calibration graph and S is standard deviation

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linearity of anodic peak current of blank solution for 5 measurements [49]. In addition, the

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obtained LOD (10.18nM) was compared with other reported modified electrodes as in the table.2 and LOQ for DA was found to be 34.32nM.The proposed electrode exhibited lower detection

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limit than those reported [55-58] as shown in Table 2.

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> Fig.9 and Table-2<

3.7 Simultaneous determination of DA, PA and FA

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Fig. 10A shows the cyclic voltammograms recorded for the tristary mixture of 4×10-6 M DA,

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3×10-6 M PA and 2×10-6 M FA at the BCPE (dashed line) TiO2-WO3NPs/MCPE (solidline).The three peaks obtained at BCPE were less sensible and TiO2-WO3NPs/MCPE exhibits well defined sharp peaks with enhanced current. The TiO2-WO3NPs/MCPE has well resolved the voltammetric peaks of DA, PA and FA located at the potential 0.132V, 0.389V and 0.661V, respectively. The peak to peak separation of DA-PA and PA-FA was found to be 0.257V and 0.272V.This result was sufficient for the simultaneous measurement of DA, PA and FA in a mixture as shown in scheme 1. Because of the higher current sensitivity and absence of background current, differential pulse voltammetry (DPV) was employed for the simultaneous 9

Journal Pre-proof determination of DA, UA and PA in 0.2 M PBS of pH 7.4 as shown in Fig.10B. The three analytes showed their oxidation potentials at 0.054V DA, 0.325V PA and 0.614V for FA respectively. The peak separation was (DA-PA) 0.271V and (PA-FA) 0.289V. So this result was good enough for the electroanalysis of DA, PA and FA in a mixture. > Fig.10 and Scheme-1<

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3.8 Interference study of the TiO2–WO3NPs/MCPE

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The interference investigation was performed in the mixture of samples containing DA, PA and

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FA at the TiO2-WO3NPs/MCPE. The concentration of one species was changed, whereas the others were kept constant. From the Fig 11a. It can be seen that the peak current of DA was

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proportional to its concentration which was increased from 4×10-6M to 9×10-6M when keeping

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the concentration kept constant of PA to 10×10-6 and FA to12×10-6M. There were no change in the peak current and peak potential occurred for PA and FA. Similarly, Fig 11b and Fig 11c self

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explains the concentration effect of PA from 10×10-6 to 15×10-6 M and FA from 12×10-6 to

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18×10-6 M respectively. These results show that the DA, PA and FA exist independently in their

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mixtures of samples. To study the effect of concentration of DA, DPV technique was used. The concentration of DA was varied from 4×10-6M to 9×10-6 M. (inset) Fig.11a shows that the graph of Ipa verses concentration of DA shows linear relationships ranging from 4×10-6M to 9×10-6M with the linear regression equation Ipa (µA) = 2.80(C0 10-7M/L) + 0.18 (10-6A) respectively. The correlation coefficient was 0.9979. > Fig.11a, Fig.11b and Fig.11c < 3.9. Stability and reproducibility of TiO2–WO3NPs/MCPE

10

Journal Pre-proof The reproducibility of the proposed method for determining DA was tested in the PBS (pH.7.4) containing 15µM by repeating for 10 times. The results showed good reproducibility of the modified electrode with a relative standard deviation of 2.3% and 3.4% for DA respectively. After each determination the modified electrode was washed with PBS and scanned using CV in the blank PBS until the oxidation response wave disappeared at 0.05 Vs -1 in the potential range of −200 to 600mV. After a week exposure of the modified electrode in air, it was found that the

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electrochemical activity of the TiO2-WO3NPs/MCPE over the determination of DA remained

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almost the same, which indicated the good reproducibility and stability of the modified electrode

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[59].

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3.9.1. Analytical applications of TiO2–WO3NPs/MCPE

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Factual implementation of TiO2-WO3NPs/MCPE was illustrated by measurable determination of DA in human blood serum sample. The sequence followed was: 5 mL of human blood serum

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sample without any pretreatment was diluted to 250 mL with pH 7.4 phosphate buffer. Distinct

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amount of this solution was blended with a known concentration of DA solution to acquire distinct concentration of pierced DA. Likewise, a drug injection capsule (tablet) consisting

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100mg dopamine hydrochloride in 50ml antisepticised water (Sterile Specialties India Private Ltd) was suitably diluted to supply distinct known standard concentration of which were examined by CV using the TiO2-WO3NPs/MCPE. Each demonstration was carried out at least 4 times and the outcome is presented in Table 3. The obtained recovery and relative standard deviation (RSD) was good displaying satisfactory performance of the TiO2-WO3NPs/MCPE [6062]

> Table-3 <

4. Conclusion

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Journal Pre-proof In this present work, we report the synthesis and characterization of TiO2, WO3 and TiO2WO3NPs. The electrochemical response of DA at bare CPE and TiO2-WO3NPs/MCPE were studied by cyclic voltammetric Technique. From the effect of pH study on DA, shows the equal number of electrons and protons contribution in electrochemical reaction and scan rate study shows the adsorption controlled process of TiO2-WO3NPs/MCPE towards DA. TiO2WO3NPs/MCPE of DA concentration, a low detection limit of 10.18nM and limit of

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quantification 34.32 nM. The TiO2-WO3NPs/MCPE exhibited good stability, repeatability and

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reproducibility towards DA. The TiO2-WO3NPs/MCPE proved to be effective sensors towards

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electrochemical investigation of DA in the presence of PC and FA. The obtained results found in

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the present work shows the fabricated TiO2-WO3NPs/MCPE acts as a good biosensors in the

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determination of biological important molecules and developing electroanalytical applications. 5. References

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Journal Pre-proof Figure Captions Scheme 1 Oxidation mechanism of DA, PA and FA. Fig.1

XRD of prepared (A) TiO2 (B) WO3 and (C) TiO2-WO3NPs. SEM images of (A) TiO2 (B) WO3 and (C) TiO2-WO3NPs.

Fig.3

TEM images of prepared (A) TiO2 (B) WO3 and (C) TiO2-WO3NPs.

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Fig.4A Energy dispersive spectrum of prepared TiO2NPs.

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Fig.2

Energy dispersive spectrum of prepared WO3NPs.

Fig.4C

Energy dispersive spectrum of prepared TiO2-WO3NPs.

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Electrochemical response of DA at different percentage weight (0.4, 0.6, 0.8, 1.0 and

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Fig.5.

-p

Fig.4 B

1.2 %)of TiO2-WO3NPs modifiers in CPE.

Cyclic voltammogramsof2×10-6MDA in 0.2M PBS of pH 7.4 at bare CPE (dashed line)

na

Fig.6.

Cyclic voltammograms obtained for the 2×10-6MDA, scan rate of 50 mV/sat TiO2-

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Fig.7.

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and TiO2-WO3NPs/MCPE (solid line).

WO3NPs/MCPE in various pH [(a) 5.8, (b) 6.2, (c) 6.6, (d) 7.0, (e) 7.4, (f) 7.8 and (g) 8.2] PBS solutions and (inset) pH versus the anodic peak potential (Epa). Fig.8

Cyclic voltammograms of 2×10-6MDA at different scan rate [(a) 50, (b) 100, (c) 150,(d)

200, (e) 250, (f) 300, (g) 350, (h) 400, (i) 450 and (j) 500 mV/s] at TiO 2WO3NPs/MCPEpresence of 0.2 M PBS of pH 7.4 and (inset) Graph of anodic peak current (Ipa) versus the scan rate (ν).

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Journal Pre-proof Fig.9 Cyclic voltammograms of TiO2-WO3NPs/MCPE in 0.2M PBS solution of pH 7.4 with different concentration DA [(a) 2×10-6 M, (b) 4×10-6 M , (c) 6×10-6 M , (d) 8×10-6 M, (e) 10×10-6 M, (f) 12×10-6 M, (g) 14×10-6 M, (h) 16×10-6 M , and (i) 18×10-6 M] and (Inset) Graph of Ipa versus concentration of DA. Fig.10 (A) Simultaneous determination of cyclic voltammograms4×10-6 M DA, 3×10-6 M PA

of

and 2×10-6 M FAin 0.2 M PBS of pH 7.4 at BCPE (dashed line) and TiO2-WO3NPs/MCPE(solid

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line) andalso studed the (B) differential pulsevoltammogram.

Fig. 11a. Differential pulse voltammograms of (a) 4×10-6 M (b) 5×10-6 M(c) 6×10-6 (d) 7×10-6 (e)

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8×10-6and(f) 9×10-6 DA in 0.2 M PBS of pH 7.4 in the presence of 10×10-6 M PA and 12×10-6

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MFA at TiO2-WO3NPs/MCPE.(Inset) Graph of Ipa versus concentration.

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Fig. 11b. Differential pulse voltammograms of (a) 10×10-6 M (b)11×10-6 M(c) 12×10-6 (d)

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13×10-6 (e) 14×10-6and(f) 15×10-6 PA in 0.2 M PBS of pH 7.4 in the presence of 4×10-6 M DA

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and 12 × 10-6M FA at TiO2-WO3NPs/MCPE. .(Inset) Graph of Ipa versus concentration. Fig. 11c. Differential pulse voltammograms of (a) 12×10-6 M (b)13×10-6 M(c) 14×10-6 (d) 15×10(e) 16×10-6and(f) 17×10-6 FA in 0.2 M PBS of pH 7.4 in the presence of 4×10-6 M DA and

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10×10-6 M PA at TiO2-WO3NPs/MCPE. .(Inset) Graph of Ipa versus concentration. Table. 1 Electrochemical parameters of DA at different scan rates. Table. 2 Comparison of different modified electrodes for DA determination Table 3

Determination of DA in human blood serum and drug injection sample (number of

trials =4) at TiO2-WO3NPs/MCPE

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(mV s−1)

∆Ep

k0(s−1)

50

0.035

0.122

100

0.037

0.294

150

0.039

0.318

200

0.040

0.435

250

0.042

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300

0.046

350

0.049

0.735

400

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Table 1-Electrochemical parameters of DA at different scan rates.

0.050

0.724

0.053

0.778

0.056

0.883

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500

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450

0.552

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0.667

Journal Pre-proof Table 2-Comparison of different modified electrodes for DA Electrodes

Detection limit (µM)

Techniques

Reference

0.3

DPV

[63]

Carbon nanotubes paste electrode modified with ferrocenedicarboxylic Acid

1.1

DPV

[64]

Poly (DL- serine/SiO2)/CPE

0.1

DPV

[65]

Poly(brilliant blue) modified CPE

0.6

Bicopper complex modified GCE

1.4

ZnO NWs/ITO

6.4

LDH/CILE

5.0

[66]

DPV

[67]

CV

[68]

DPV

[69]

DPV

[70]

0.3

DPV

[71]

0.45

SWV

[72]

1.5

CV

[73]

1.51

DPV

[74]

0.25

DPV

[75]

Rod shaped CuO nanoparticles/MCPE

0.18

DPV

[76]

TiO2–WO3 nanocomposite/MCPE

0.0012

CV

This work

Ag NPs/CNTs

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CCE/ferrocene

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MWCPE

Poly(MG)/CPE

2.09

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Banana/MWCNTs/MCPE

SDS/polyglycine/ phthalamide/CPE

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Nanostructured polyaniline/ tungstophosphoric acid CPE

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Journal Pre-proof Table 3- Determination of DA in human blood serum and drug injection sample (number of trials =4)

Samples

DA added

RSD%

Recovery

0. 5

0.092

2.56

91.95

0. 6

0.193

3.34

100.95

0. 7

0.276

3.46

99.87

0.5

0.135

(mg/ml)

100.05

0.185

2.19

99.70

0.270

3.04

98.30

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0.6 0.7

1.58

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Blood sample

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Drug sample

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(mM)

Found

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Author contribution

Dr. N.B.Ashok is worked completely as a Ph.D. Student Dr.B.E.Kumara Swamy is the main author for this work whom he worked for the Ph.D. Dr.H.Jayadevappa is one of the Co-Guide for Dr.N.B.Ashok

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Declaration of Interest Statement

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Dr.S.C.Sharma is the Director and contributed for the queries and all other characterization and Discussions Part and Eminent Scientist.

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There is no Conflict of work and authors are completely agreed to publish this manuscript in this journal

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Graphical abstract

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Mixed titanium oxide and tungsten trioxide nanoparticles (TiO2-WO3NPs) were synthesized and used as electrochemical sensor for simultaneous detection of Dopamine, Paracetamol and Folic acid.

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Highlights

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Mixed titanium oxide and tungsten trioxide nanoparticles (TiO2-WO3NPs) was prepared by using hydrothermal method. Prepared TiO2-WO3NPs was used as a modifier in preparing carbon paste electrode (CPE). Simultaneous determination of dopamine (DA), paracetamol (PA) and folic acid (FA) was studied. TiO2-WO3NPs/MCPE shown well resolved anodic peak for DA, UA and FA mixture. Stability, reproducibility and analytical applications of TiO2-WO3NPs/MCPE were determined.

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