Development of a sensor for thiosalicylic acid at MWCNT modified gold

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ScienceDirect Materials Today: Proceedings 18 (2019) 723–730

www.materialstoday.com/proceedings

ICN3I-2017

Development of a sensor for thiosalicylic acid at MWCNT modified gold Anand R. Kulkarnia, Nagaraj P. Shetti b,*, Shweta J. Malode b, Raviraj M. Kulkarnia a

Department of Chemistry, K. L. S. Gogte Institute of Technology (Autonomous), affiliated to Visvesvaraya Technological University Belagavi590008, Karnataka, India. b

Electrochemistry and Materials Group, Department of Chemistry, K. L. E. Institute of Technology, Hubballi-580030, Affiliated to Visvesvaraya Technological University, Belagavi, Karnataka, India.

Abstract Development of nano level based sensor for the electrochemical performance of thiosalicylic acid by fabrication of multiwalled carbon nanotubes on glassy carbon electrode was made. Employing cyclic voltammetry and square wave voltammetry techniques in pH 4.2 phosphate buffer solution, parameters effect was estimated by varying pH, accumulation time, scan rate, excipients, and analyte concentration. Number of electrons, protons involved in the reactions and also heterogeneous rate constant value was determined. The proposed sensor was applied for the determination of analyte in pharmaceutical and human urine samples. The linear response was obtained in the concentration range studied with lower quantification limit value. Reaction mechanism for electrochemical oxidation of thiosalicylic acid was proposed. The modified sensor showed an excellent sensitivity, reproducibility, repeatability etc. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Nanotechnology: Ideas, Innovations & Initiatives-2017 (ICN:3i2017). Keywords: Thiosalicylic acid, Multiwalled carbon nanotubes, Modified gold electrode, Cyclic voltammetry, Square Wave Voltammetry, Analytical applications

2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Nanotechnology: Ideas, Innovations & Initiatives-2017 (ICN:3i2017).

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Introduction

2-Mercaptobenzoic acid (Scheme 1), known as thiosalicylic acid (TSA) contains carboxylic and sulfohydryl groups. Respiratory, allergic and inflammatory diseases causes can be treated by TSA. It is well known for its applications to cosmetics industries, in the manufacture of vaccines as activating bacteriostatic agent etc [1-9]. Literature data showed few techniques for the electro oxidation and analysis of TSA which includes HPLC, electro analytical methods and chromatographic techniques [10, 11]. These methods are convoluted, pricey and consume time. Thus determination of TSA by studying its electrochemical behavior is very fundamental. Till now no research was found on the electro sensing of TSA using any nanoparticles modified gold electrode (GE). In the present paper, we have premeditated the applications of multi-walled carbon nanoparticles (MWCNTs) in the electro determination of TSA by applying various voltammetric techniques with incomparable outcomes.

Scheme 1. Chemical structure of Thiosalicylic acid

The present work hopes to construct a sensor using MWCNTs as modifier for GE. Modified sensors are meant to upgrade the sensitivity to acquire innovative sensor owing to its distinctive properties such as small residual background current, huge applicable potential window, the reproducibility, low outlay, permanence and quick [12-14]. MWCNTs got number of advantages on the electrosensing platform due to their incomparable properties such as substantial surface range, high conductivity, significant mechanical strength, electrocatalytic activity making electron transfer faster and fouling resistance [15, 16].

2. Experimental 2.1. Instrumentation and chemicals A CHI Company, D630 electrochemical analyzer is utilized to carry out voltammetric measurements. The analyzer was incorporated by three electrode system in a glass cell, main working sensor as MWCNTs nanoparticles modified gold electrode (MWCNTs-GE), auxiliary sensor as platinum wire, and reference sensor as an Ag/AgCl filled with 3.0 M KCl correspondingly. The pH measurements were performed utilizing pH meter (Elico Ltd., India). From Sigma Aldrich, purchased all the chemicals essential for this study and water used was double distilled. The TSA stock solution (1.0 mM) was prepared using ethanol. Phosphate buffer solution used as supporting electrolyte [17] with different pH varying from 3.0 to 11.2.

2.2. Preparation of modified electrode MWCNTs suspension was primed by dispersing 1mg of MWCNTs in 10 ml ethanol and subjected to sonication for about 15 minutes. Before each measurement, the working electrode was polished vigilantly with Al2O3 (0.3 micron) using a muslin cloth. Then cleaned well by rinsing the polished GE in ethanol and followed by double distilled water to eliminate the settled Al2O3 particles from the surface. So cleaned GE was coated with 10 mL of MWCNTs suspension and dried. Then the modified GE was made active in pH 4.2 by CV scan in the working potential range till stable CV was found. Finally the pretreated electrode transferred to 10 ml glass cell containing pH 4.2 with analyte.

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2.3. Procedures for pharmaceutical preparations Stock solution of TSA containing tablets (purchased from a local pharmacy) equivalent to 1.0 mM TSA was prepared in 100 mL volumetric flask. Sonicated for complete dissolution and then filtered. The filtrate was used for analyzing TSA performing SWV technique. Urine samples from healthy persons were centrifuged (4383 G at 25 ± 0.1 0C) for 5 minutes. The test solution was prepared by spiking the samples filtrate with the known amount of TSA (1.0 mM).

3.

Results and discussion

3.1 Modified electrode surface area and characterization Modified gold electrode active surface area was intended utilizing Randles-Sevcik equation. To attain the result, 0.1 M KCl was taken as supporting electrolyte and the test solution was K3Fe (CN)6 with concentration of 1.0 mM and diffusion coefficient (D0) of 7.6 x 10-6 cm2 s-1 [18]. From the calculation, we found 0.046 cm2 area for GE while MWCNTs modified GE shows higher area than the bare. Ip = (2.69 x 105) n3/2 A D01/2 ν1/2 C0* 3.2 Influence of preconcentration time and modifier amount The study of preconcentration time impact was carried out in a range of 0-60 s. The utmost oxidation peak was reported at 30 s (Fig. 1). This effect indicates drenched adsorption on the modified sensor was achieved at the accumulation time of 30s. Hence for further studies carried out with accumulation time of 30s. Voltammograms were recorded using fabricated GE by varying the amount of suspension of MWCNTs nanoparticles on the sensing surface and the fluctuations in the peak current as well as in the peak potential were noted. Finally, from the study we come to know that the usage of 0.4 µL of nano suspension was found be best possible to construct modified GE. 20 Peak Current (Ip/µA)

Peak current (Ip/µA)

16 12 8 4 0

0

15

30

Time (sec)

45

60

16 12 8 4 0

0.05

0.1

0.2

0.3

0.4

0.5

[MWCNTs]

Fig. 1: (A) influence of time on the peak current; (B) Influence of modifier amount on the peak current

3.3 Voltammetric behavior of TSA CVs of GE and MWCNTs-GE (Fig. 2), in the presence and absence of 1.0 mM TSA at 50 mVs−1 in pH 4.2 PBS. An oxidation peak with superior temperament was observed at MWCNTs-GE while at bare GE a deprived peak was found. In the active presence of 1.0 mM TSA, an irreversible behavior through moderately weak peak

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currents occurred at anodic potential (Ep) = 1.1605 V with peak current 6.013 µA for bare GE. While at MWCNTsGE, an irreversible behavior through an accentuated anodic peak with Ep = 1.1605 V with peak current 12.07 µA correspondingly.

14

d

12

Peak Current (Ip/µA)

Current /µA

c b a

10

Current (µA) Potential (V)

8 6 4 2 0

Bare Gold

MWCNTs/Gold

Potential/V (vs. Ag/AgCl) Fig. 2. Voltammetric behavior of 1.0 mM TSA in pH 4.2 PBS (I = 0.2 M) at scan rate = 0.05 Vs-1; Acc. Time= 30s: (a) Buffer at GE; (b) analyte at GE; (b) buffer at MWCNTs-GE; (c) analyte at MWCNTs-GE. (A) Variation in peak current and peak potential at different electrodes.

3.3 Effect of supporting electrolyte The electrochemical response of 1.0 mM TSA was studied by CV technique, over the pH range of 3.0-11.2 in 0.2 M PBS (Fig. 3). As the pH of PBS solution was increased, there was less positive shifting of peak potentials, suggesting the involvement of protons in the reaction and easy oxidation. At pH 4.2, highest peak current was noticed for TSA detection and therefore, for further analytical studies pH 4.2 was chosen (Fig. 3B). From the plot Ep versus pH (Fig. 3A), acquired linear equation is as follows; Ep= -0.055 pH + 1.351; R2 = 0.928. The slope value indicates that in the TSA oxidation, protons and electrons were involved in unequal number [19]. 1.4

6

4.2

7

5 3

1.2

1.0

8 0.8 2

4

2

4

pH

6

8

25

Ip/µA

Current /µA

9

Ep/Vs-1

y = -0.055x + 1.351 R² = 0.928

20

15

Potential/V (vs. Ag/AgCl)

pH

6

8

Fig. 3. CVs obtained for 1.0 mM TSA in PBS of different pH at MWCNTs-GE; Scan rate = 0.05 Vs-1; Acc. Time = 30s; Influence of pH on; (A) Ep / V of TSA. (B) Ip / µA of TSA.

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3.4 Sweep rate effect The voltammograms of TSA were recorded on the MWCNTs-GE surface at varying scan rates in pH 4.2 by CV (Fig. 4). From the study, the slope of log Ip vs. log υ plot, results with a straight line and the slope was found to be 0.962, which proves that the present electrochemical reaction is adsorption controlled process. The slope value is closest to the theoretical value 1.0 for an adsorption controlled process [20] corresponding to the following equation: log Ip (µA) = 0.962 log υ + 2.394; R2 = 0.992. In addition a good linear relation was observed between Ep and log ν with the regression equation: Ep (V) = 0.080 log υ + 1.139; R2 = 0.988. Scan rate and Ep relationship for a process involved by sensor can be stated by Laviron’s theory [21]. According to Bard and Faulkner [22],  can be calculated as, p= Ep - Ep/2=

47.7

mV

n y = 0.962x + 2.394 R² = 0.992

1.7 1.4

log Ip/µA

9

1.1 0.8

Current /µA

0.5 0.2 -2.4

-1.8

-1.2

-0.6

log ν/ Vs-1 y = 0.080x + 1.139 R² = 0.988

1.1

1

Ep/Vs-1

1.05

1 0.95 -2.2

Potential/V (vs. Ag/AgCl)

-1.7

-1.2

-0.7

log ν/ Vs-1

Fig. 4. Cyclic voltammograms of 1.0 mM TSA in pH 4.2 (I = 0.2 M) at MWCNTs-GE with scan rate of: (1) 0.01 to (9) 0.2V s-1. Acc. Time= 30s; Plot of; (A log Ip / µA versus log υ / Vs-1. (B) Ep / V log υ / Vs-1.

The ‘α’ found to be 0.56 and k0 as 3.707 x 103 s-1, from Ep versus log υ intercept. Further, the number of electron (n) transferred in the electro-oxidation of TSA was calculated to be 1.34. Based on the number of protons and electrons concerned, we proposed a reaction mechanism (Scheme 2).

Scheme 2. Reaction mechanism for electro-oxidation of TSA

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Analytical applications

4.1. Calibration curve and detection limit Square wave voltammograms (SWVs) Fig. 5 present the TSA concentration variation at MWCNTs-GE ranging between 0.01 µM to 0.1 µM in pH 4.2 with an equation: Ip (μA) =20.08 C (µM) + 1.863; R2 = 0.988. Detection and quantification values were attained to be 2.35x10-8M and 7.84x10-8M by using following equations 3S/M and 10S/M (S=blank standard deviation, M= slope) respectively [23]. The current results recommended to be highly sensitive with low detection and quantification limit for TSA compared to sensor performances of the earlier reported publications.

5

6.0 y = 20.08x + 1.863 R² = 0.988

Ip/µA

Current /µA

4.0

2.0

0.0

1

0

0.02 0.04 0.06 0.08 0.1 0.12 Concentration (µM)

Potential/V (vs. Ag/AgCl) Fig. 5. SWVs with increasing concentrations of TSA in pH 4.2 PBS at MWCNTs-GE with acc. time = 30s: (1) 0.01 to (4) 0.1 µM . Inset: Plot of concentration versus Ip / µA.

4.2. TSA in pharmaceutical and urine samples The pharmaceutical and urine samples were subjected to TSA analysis by SWV technique. By utilizing the calibration graph, recovery studies were carried out and results are showed in Table 1. Table 1. Application of SWV for the determination of TSA in pharmaceutical samples and spiked human urine samples. Pharmaceutical Samples

Spiked (10-6 M)

Detected (10-6 M)

Recovery

1

1.0

0.98

98.0

2

5.0

4.53

90.6

3

8.0

7.73

96.6

4

10.0

9.76

97.6

Urine Samples

Spiked (10-4 M)

Detected (10-4 M)

RSD

% RSD

1

0.1

0.0958

0.0323

3.23

2

0.2

0.1829

0.0355

3.52

3

0.5

0.4574

0.0374

3.74

*Average five readings

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4.3. Effect of excipients The results obtained by the study of interference of excipients on TSA electro behavior indicates that the potential of the drug changed to some extent but did not exceed ±5%, which suggests that TSA reactions at the sensing base, does not affects the existence of any metabolites tested. Thus, TSA detection and determination at MWCNTs at GE can be efficiently employed for TSA detection Fig. 6. 4.355543419

4.5

Signal change %

4 3.5

3.700163845 3.345166576

3.181321682

2.949208083

3 2.348443474

2.5 2 1.5

1.843255052 1.324412889

1

0.491534681

0.5 0

Fig. 6. Excipient effect on TSA electrobehaviour

4.4.

Repeatability and Reproducibility of the MWCNTs-GE

To study the Repeatability and Reproducibility of sensing electrode, the stability was checked by keeping it in an air tight container at least for 10 days. The sensor showed 96% of its initial peak current responsive for a concentration 1.0 mM TSA. An inter-day and intra-day study for the reproducibility of the sensor was explored by taking a steady concentration of analyte. Relative standard deviation (RSD) of about 2.6% was noticeable for good reproducibility of the sensor for TSA detection. 5. Conclusions In present work MWCNTs nanoparticles were found to be an efficient modifier on the surface of gold electrode. These nanoparticles fabricated on sensing tool found proficient for TSA quantification. Cyclic voltammetry, square wave voltammetry techniques were utilized. Compared to bare GE, the modified GE shows improved results with high sensitivity and selectivity towards the analysis in pH 4.2 PBS. From the acquired data, adsorption controlled process and two electrons-protons involvement was viewed. Compared to reported works, this study is very well-suited because of its selectivity and lower detection limit value. Good recovery results were obtained from the analysis of urine and pharmaceutical samples. Addition to this excipients study showed no interference on the TSA analysis and its determination, thus the present study can be considered specific.

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References [1] J. McCaffrey, W. Henderson, B.K. Nicholson, J.E. Mackay, M.B. Dinger, J. Chem Soc Dalton Trans., 36 (1997) 2577–2586. [2] A. K. Chhakkar, L. R. Kakkar Fresenius, J. Anal. Chem. 347 (1993) 483–487. [3] M. J. Gismera, J. R. Procopio, M. T. Sevilla, L. Hernandez, Electroanalysis, 15 (2003) 126–131. [4] M. Aydin, N. Arsu, Y. Yagci, Macromol Rapid Commun., 24 (2003) 718–722. [5] D. Shander, G. Ahluwalia, D. Grosso U. S. Patent, 5 (1992) 411,991 A [6] H. Jacobelli (2005) US Patent, 20,050,267,095 A1 [7] J. H. Wiener, Y. Kloog, V. Wacheck, B. Jansen, J. Invest Dermat., 120 (2003) 109-114. [8] Canada Communicable Disease Report No. 9 (2002) 28, 69-73. [9] G. Elad, A. Paz, R. Haklai, D. Marciano, A. Cox, Y. Kloog, J. Biochem Biophy Acta, 1452 (1999) 228–232. [10] J.R. Procopio, M.P. Silva, M.C. Asensio, M.T. Sevilla, L. Hernandez, Talanta, 39 (1992) 1619–1623. [11] D.S. Nayak, N.P. Shetti, J. Surfactants. Deterg., 19 (2016) 1071-1079. [12] N. P. Shetti, D. S. Nayak, S. J. Malode, R. M. Kulkarni, J. Electrochem. Soc. 164 (2017) B3036-B3042. [13] S. J. Malode, J. C. Abbar, N. P. Shetti, S. T. Nandibewoor, Electrochim. acta, 60 (2012) 95-101. [14] N. P. Shetti, D. S. Nayak, S. J. Malode, R.M. Kulkarni, Sens. Bio-sensing res. 14 (2017) 39-46. [15] V. Erady, R. J. Mascarenhas, A. K. Satpati, S. Detriche, Z. Mekhalif, J. Delhalle, A. Dhason, Mater. Sci. Eng. C. Mater. Biol. Appl. 76 (2017) 114-122. [16] A. Afkhami, F. Soltani-Felehgari, T. Madrakian, H. Ghaedi, Biosens. Bioelectron. 51 (2014) 379-385 [17] D.K. Gosser, (ed) Cyclic Voltammetry. VCH (1994) New York. [18] T. Iwasita, Electrochim. Acta, 47 (2002) 3663–3674. [19] S.J. Malode, N.P. Shetti, S.T. Nandibewoor, Colloids Surf. B Biointerfaces, 97 (2002) 1–6. [20] N.P. Shetti, D.S. Nayak, S.J. Malode, R.M. Kulkarni, J. Electrochem. Soc., 164 (2017) B3036-B3042. [21] E. Laviron, J. Electroanal. Chem. 101 (1979) 19-28. [22] A. J. Bard, L. R. Faulkner. Electrochemical methods: fundamentals and applications. 2nd ed. New York: John Wiley and sons; 2004 [23] N. P. Shetti, D. S. Nayak, S. J. Malode, Sens. Actuators B. 247 (2017) 858-867.