ZnO nanoparticles modified sensor for the electroanalysis of thiosalicylic acid

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ScienceDirect Materials Today: Proceedings 18 (2019) 710–716

www.materialstoday.com/proceedings

ICN3I-2017

ZnO nanoparticles modified sensor for the electroanalysis of thiosalicylic acid Nishank Navelkara, Nagaraj P. Shettib,*, Shweta J. Malodeb, 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, Karnataka, India.

Abstract A nano level detection of thiosalicylic acid and its analysis by sensing method has been developed at zinc oxide nanoparticles modified glassy carbon electrode by employing voltammetric techniques in pH 3.0. The modified sensor was subjected to test the influence of parameters like pH, accumulation time for thiosalicylic acid drug was studied by employing cyclic voltammetry and scan rate, excipients, thiosalicylic acid concentration variation by using square wave voltammetry technique for quantitative determination in phosphate buffer. Heterogeneous rate constant value was also determined. The zinc oxide nanoparticles modified glassy carbon electrode sensor was employed for the determination of thiosalicylic acid in pharmaceutical samples. The concentration range studied in square wave voltammetry technique exhibits lower values of detection limit and quantification of thiosalicylic acid. A possible mechanism of electrochemical oxidation of thiosalicylic acid was proposed. © 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: ZnO nanoparticles, Thiosalicylic acid, Cyclic voltammetry, Square Wave Voltammetry, Pharmaceutical sample

* Corresponding author. Tel.: +91 9611979743; fax: 0836 – 2330688 E-mail address: [email protected]

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).

N. Navelkar et al. / Materials Today: Proceedings 18 (2019) 710–716

1.

711

Introduction

Thiosalicylic acid (TSA), also known as 2-Mercaptobenzoic acid (Scheme 1) with carboxylic and sulfohydryl groups useful in number of disease treatments such as respiratory, allergic and inflammatory. It is also applicable to cosmetics industries and in the manufacturing process of vaccines as activating bacteriostatic agent etc [1-9]. From literature survey, few techniques for the determination of TSA are reported, such as, HPLC [10], electro analytical methods [11] and other chromatographic techniques. The reported methods are complicated, expensive and consume time. Analysis of TSA by studying its electrochemical behavior is one of the important contributions to its domain.

Scheme 1. Chemical structure of Thiosalicylic acid (TSA)

Till now no research was found on the electro sensing of TSA using any nanoparticles modified glassy carbon electrode (GCE). In the present paper we have studied applications of ZnO nanoparticles in the electrochemical determination of TSA by applying various voltammetric techniques with good results. Amongst the various nanoparticles, zinc oxide nanoparticles gained a unique space due to spectacular surface properties, which enforced scientists to develop them as modifiers [12, 13]. In addition the primary base chosen was GCEs which also have magnetized a wide range of researchers in the area of modified sensors due to its unique properties with small background current, large potential range, stability and easily renewal surface, with diverse sorts of modulators etc [14, 15]. TSA determination involves studying the effect of pH, accumulation time, modifier amount, scan rate and concentration variation etc. 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 ZnO nanoparticles modified glassy carbon electrode (ZnO-GCE), 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 [16] with different pH varying from 3.0 to 11.2. 2.2 Preparation of modified electrode A white suspension of ZnO nanoparticles was prepared by dispersing about 1mg of nano ZnO in 10 ml ethanol using ultrasonicator. Before each CV measurement, the GCE was polished cautiously with Al2O3 (0.3 micron) using a muslin cloth. Then cleaned well by rinsing the polished GCE in ethanol and followed by double distilled water to eliminate the settled Al2O3 particles from the surface. So cleaned GCE was coated with 10 µL of nano ZnO suspension and dried. Then the modified GCE was functionalized in pH 3.0 by CV scan in the working potential range till stable CV was found. Finally the pre-treated electrode transferred to 10 ml glass cell containing pH 3.0 with analyte.

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2.3 Procedures for pharmaceutical preparations and spiked human urine samples TSA containing tablets were purchased from a pharmacy. Stock solution equivalent to 1.0 mM TSA was prepared in 100 mL volumetric flask and sonicated correctly for complete dissolution, clean supernatant liquid of the aliquots were taken and diluted with pH 3.0. Using SWV technique and adopting standard addition method TSA analysis was carried out in the syrup. Likewise excipients effect also studied to check the proposed method accuracy. From healthy volunteers, urine samples were collected. The collected samples 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 active surface area of the sensor was calculated utilizing Randles-Sevcik equation. To obtain 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 [17]. From the calculation, we found 0.040 cm2 area for GCE while nano ZnO modified GCE shows higher area than the bare. Ip = (2.69 x 105) n3/2 A D01/2 ν1/2 C0*

(1)

3.2 Influence of pre-concentration time and modifier amount The study of pre-concentration time impact was carried out in a range of 0-60 s. The utmost oxidation peak was reported at 0 s (Fig. 1). This effect indicates drenched adsorption on the modified sensor was achieved without accumulation time. Hence for further studies carried out with no accumulation time. Voltammograms were recorded using fabricated GCE by varying the amount of suspension of ZnO 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 0.5 µL of nano ZnO suspension was found be optimum to fabricate modified GCE. Peak current (Ip/µA)

6

4

2

0

0

15

30

45

60

Time (sec) Fig. 1. Effect of accumulation time

3.3 Electrochemical behavior of TSA The CV obtained in pH 3.0 with sweep rate of 50 mVs−1 at GCE and ZnO-GCE, in the existence and absence of 1.0 mM TSA is exhibited in Fig. 2. In the active existence of 1.0 mM TSA at GCE with low current while an enhanced anodic peak seen at ZnO-GCE. No reduction peaks were observed indicating that the present reaction was entirely irreversible process.

N. Navelkar et al. / Materials Today: Proceedings 18 (2019) 710–716

713

Current /µA

d

b

c a

Potential/V (vs. Ag/AgCl)

Fig. 2. Electrochemical behavior of TSA 1.0 mM in pH 3.0 with scan rate = 0.05 Vs-1; (a) blank GCE; (b) CV of 1.0 mM TSA at GCE; (c) blank ZnO-GCE; (d) CV of 1.0 mM TSA at ZnO-GCE.

3.4 Effect of supporting electrolyte Variation in supporting electrolyte pH results change in the electrochemical behavior of TSA (Fig. 3). The studied pH range was 3.0-11.2 with sweep rate 50mVs-1. From the acquired data, at 3.0 pH an accentuated performance of TSA was noticed and thus 3.0 pH only opted for further studies. With pH of supporting electrolyte the peak current goes on decreasing and no peaks were observed above 6.0 pH. From the collected data, graphs were plotted to know the potential, peak current relation with pH (Fig. 3A & 3B) & found linearity in Ep v/s pH, i.e. Ep= 0.055 pH + 1.467; R2 = 0.998. The value of slope indicates that in the TSA oxidation, there is involvement of unequal number of protons and electrons [18].

Potential/V

1.4 3

.

1.2 /V p

1.1

E

(A)

1.0 2

6

5

3

4

5

pH

6

7

8

8 4.2

7 8

Current/µA

Current/µA

1 -

.

1.3

7 6 5 /µA p I

4 3

(B)

2 2

4

pH 6

8

Potential/V (vs. Ag/AgCl) Fig. 3. Study of effect of pH using of 1.0 mM TSA by CV technique at ZnO-GCE; Scan rate = 0.05 Vs-1; (A) Effect of pH on the peak potential Ep/V; (B) Influence of pH on the peak current Ip /µA.

3.5 Influence of scan rate LSV technique was adapted to study the sweep rate impact on TSA behavior at the ZnO-GCE in 3.0 pH (Fig. 4). From the study we observed that, there is positive shift of potential with the enhancement of current for each scan rate raise (Fig. 4A). In addition to this, adsorption controlled behavior was observed from the slope value of log Ip v/s log υ, 0.779; which is nearer to 1.0 theoretically (Fig. 4B) [19, 20]. The corresponding equation is log Ip (µA) = 0.330 log υ + 0.779; R2 = 0.974. The relation between Ep and log ʋ was also found to be linear (Fig. 4C). Scan rate and Ep relationship for a process involved by sensor can be stated by Laviron’s theory [21].

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N. Navelkar et al. / Materials Today: Proceedings 18 (2019) 710–716

RTk0 + 2.303RT 2.303RT log Ep = E + nF nF nF

(2)

log ʋ

0

Based upon Bard and Faulkner [22] the transfer coefficient (), heterogeneous rate constant and number of electrons were calculated.

p= Ep - Ep/2=

47.7

(3)

mV

n

The ‘α’ value calculated to be 0.55 and k0 as 3.9 x 10-3 s-1. The number of electron (s) transferred in the electro-oxidation of TSA to be 2.06 ≈ 2.

.

5 .

0.75

Ip/µA

0.73

3

0.71

2

0.69

Ep/V

14

0.77

. .

.

4

1 -

/Vs p

Current/µA

Ip/ µA

1 0 0.00

(C)

(A) 0.10

ʋ/

0.20

0.67

E

0.65

0.30

-2.2 -1.7

-1 Vs

-1.2

-0.7

log ʋ/ Vs-1 4

0.8 .

0.4

log Ip Ip/µA

0.6

3

/µA p

/µA

p

I

0.2

1 (B)

0.0 -2.4

-1.8

-1.2

-0.6

2

log I

(D) 1 0.05 0.15 0.25 0.35 0.45

-1 ʋ1/2 / Vs-1 log ʋ / Vs Potential/V (vs. Ag/AgCl) Fig. 4. Impact of sweep rate on TSA in pH 10.4 at ZnO-GCE: (1) blank; (2) 0.01; (3) 0.03; (4) 0.05; (5) 0.07; (6) 0.1; (7) 0.13; (8) 0.15 V s-1. Plot of; (A) peak current (Ip / µA) versus scan rate (υ / Vs-1); (B) log Ip / µA versus log υ / Vs-1; (C) Ep / V versus log υ / Vs-1; (D) Peak current (Ip / µA) versus square root of scan rate (υ1/2 / Vs-1).

4.

Analytical applications

4.1. TSA concentration variation The peak current response towards the concentration variation was carried out by SWV technique in the range of 0.01-0.15 µM at the fabricated sensor (Fig. 5). The relative equation is: Ip (μA) = 9.34C (µM) + 0.494; R2 = 0.985. From the calculation, 2.77x10-8 of LOD and 9.24 x 10-8 of LOQ was found by using standard equations [2325]. The current research suggests highly sensitive method with low detection and quantification limit for TSA compared to sensor performances of the earlier reported publication i.e., electro-oxidation of TSA at CTAB modified GCE with LOD value 113 nM. 4.2. Urine sample analysis The spiked urine samples were prepared for the analysis by utilizing the calibration graph. Recovery values are showed in Table 1, which are agreeable for TSA quantification [26].

N. Navelkar et al. / Materials Today: Proceedings 18 (2019) 710–716

Ip/µA

2.5

µA p/ I

.

2.0

.

715

8

1.5 1.0 0.5 0.0

Current/µA

0

0.05 0.1 0.15 0.2

Concentration (µM)

1

Potential/V (vs. Ag/AgCl) Fig. 5. Study of concentration variation of TSA using SWV technique ions at ZnO-GCE: (1) Buffer; (2) 0.01; (3) 0.03; (4) 0.05; (5) 0.07; (6) 0.1; (7) 0.13; (8) 0.15µM. Inset: Plot of concentration versus peak current Ip / µA. Table 1. Application of SWV for the determination of TSA in spiked human urine samples. Spiked RSD % RSD Detected (10-4 M) (10-4 M) 1 0.1 0.0984 0.01909 1.909 2 0.5 0.4745 0.01981 1.981 3 1.0 0.9786 0.19212 1.921 *Average five readings Urine Samples

4.3. Effect of excipients and metal salts Study of excipients examined to check the TSA behavior in the existence of some general biological metabolites. The result indicates that the potential of the drug changed slightly but not exceed ±5%, which suggests that TSA reactions at the sensing base, does not affects the existence of any metabolites tested. Hence, the fabricated electrose can be efficiently employed for TSA detection. 4.4. Repeatability and Reproducibility of the ZnO-GCE The sensing electrode reliability was tested for 10 days, by conserving the prepared electrode in an air sealed container. The sensor maintained 96% of its peak current corresponding to a concentration of 1.0 mM TSA. This showed the long-standing reliability of ZnO-GCE. At constant temperature, via intra-day study the reproducibility of the sensor was explored. Taking a steady concentration of analyte, five tiresome measurements were documented. % RSD (relative standard deviation) of about 2.5 % was noticeable for good reproducibility of the sensor for TSA detection. 5.

Conclusions

In the present study, zinc oxide nanoparticles are introduced as an efficient modifier GCE surface and thus fabricated sensing electrode for TSA quantification. Cyclic voltammetry, linear sweep voltammetry and square wave voltammetry techniques were utilized. Compared to bare GCE the modified GCE shows improved results with high sensitivity and selectivity towards the analysis in pH 3.0. From the voltammetry study an irreversible, adsorption controlled process with the involvement of two electrons in the electro-oxidation process was witnessed. Contrasted with prior reports, this study is very expedient because of its selectivity and lower detection limit value. Good recovery results were obtained from the analysis of urine samples. Addition to this excipients study showed no interference on the TSA analysis and its detection.

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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, Electroanal. 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] N.P. Shetti, S.J. Malode, S.T. Nandibewoor, Anal. Methods, 7 (2015) 8673-8678. [12] R.M. Pattabi, M. Pattabi, Spectrochem. Acta, 74 (2009)195–201. [13] C.W. Chien, C.L. Liu, F.J. Chen, K.H. Lin, C.S. Lin, J. Electrochim. Acta, 72 (2012) 74–80. [14] J.M. Kauffmann, J.C. Vire, Anal Chim Acta, 273 (1993) 329–333. [15] G.D. Christain, W.C. Purdy, J. Electroanal Chem., 3 (1962) 363–367. [16] D.K. Gosser, (ed) Cyclic Voltammetry. VCH (1994) New York. [17] T. Iwasita, Electrochim. Acta, 47 (2002) 3663–3674. [18] N.P. Shetti, S.J. Malode, S.T. Nandibewoor, Bioelectrochem., 88 (2012) 76-83. [19] M.R. Smyth, J.G. Vas, Comprehensive analytical chemistry. Elsevier (1992) Amsterdam. [20] J. Wang (2006) Analytical electrochemistry, 3rd edn. Wiley, New Jersey. [21] N.P. Shetti, D.S. Nayak, S.J. Malode, R.M. Kulkarni, J. Electrochem. Soc. 164 (2017) B3036-B3042. [22] G.R. Peat, L.M. Pletcher, J. Robison, Instrumental methods in electrochemistry. Ellis Horwood, Chicherster (1985) 185–191. [23] N.P. Shetti, D.S. Nayak, S.J. Malode, R.M. Kulkarni, Sens. Biosensing Res. 14 (2017) 39-46. [24] N.P. Shetti, D.S. Nayak, G. T. Kuchinad, R. R. Naik, Electrochimica Acta, 269 (2018) 204-211. [25] N.P. Shetti, D.S. Nayak, S.J. Malode, Sens. Actuators B. 247 (2017) 858-867 [26] S.J. Malode, N.P. Shetti, S.T. Nandibewoor, Colloids Surf. B Biointerfaces, 97 (2012) 1-6.