Scholarly article on topic 'Electroanalysis of estriol hormone using electrochemical sensor'

Electroanalysis of estriol hormone using electrochemical sensor Academic research paper on "Chemical sciences"

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Abstract of research paper on Chemical sciences, author of scientific article — J.G. Manjunatha

Abstract At present, there is the whole area of research community occupied with developing of new materials and fabrication of new biosensors. With the intention to propose an effective, quick and inexpensive method for determination of biomolecules. Here in, we report the electrocatalytic oxidation of Estriol (ET) was analysed by poly (glycine) modified carbon paste electrode (PGMCPE) using cyclic voltammetry and differential voltammetry. Compared to bare carbon paste electrode (BCPE), the PGMCPE indicates good electrocatalytic activity towards the oxidation of ET in phosphate buffer solution (PBS) pH6. PGMCPE shows a linear response between concentrations of ET. The prepared modified electrode showed high voltammetric responses with sensitivity for ET, results showed it very suitable for the detection of ET at trace levels. Under the optimized conditions, the peak current was linear to ET concentration over the concentration range of 2×10−6 to 1×10−4 M using cyclic voltammetry (CV). The detection limit and limit of quantification were 8.7×10−7 M and 2.6×10−6 M. The proposed method was successfully applied for the determination of ET in the real samples.

Academic research paper on topic "Electroanalysis of estriol hormone using electrochemical sensor"

Accepted Manuscript

SENSING AND

BIO-SENSiNG RESEARCH

J.G. Manjunatha

Electroanalysis of estriol hormone using electrochemical sensor

PII: DOI:

Reference:

S2214-1804(17)30168-X doi:10.1016/j.sbsr.2017.11.006 SBSR 214

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Sensing and Bio-Sensing Research

Received date: Revised date: Accepted date:

8 October 2017 18 November 2017 22 November 2017

Please cite this article as: J.G. Manjunatha , Electroanalysis of estriol hormone using electrochemical sensor. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Sbsr(2017), doi:10.1016/ j.sbsr.2017.11.006

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Electroanalysis of Estriol Hormone Using Electrochemical Sensor

J.G. Manjunatha

Dept of Chemistry, FMKMC College, Madikeri, Mangalore University Constituent College,

Karnataka, India

ABSTRACT

At present, there is the whole area of research community occupied with developing of new materials and fabrication of new biosensors. With the intention to propose an effective, quick and inexpensive method for determination of biomolecules. Here in, we report the electrocatalytic oxidation of Estriol (ET) was analysed by poly (glycine) modified carbon paste electrode (PGMCPE) using cyclic voltammetry and differential voltammetry. Compared to bare carbon paste electrode (BCPE), the PGMCPE indicates good electrocatalytic activity towards the oxidation of ET in phosphate buffer solution (PBS) pH 6. PGMCPE shows a linear response between concentrations of ET. The prepared modified electrode showed high voltammetric responses with sensitivity for ET, results showed it very suitable for the detection of ET at trace levels. Under the optimized conditions, the peak current was linear to ET concentration over the concentration range of 2*10-6 to 1*10-4 M using cyclic voltammetry (CV). The detection limit and limit of quantification were 8.7*10-7 M and 2.6*10-6 M. The proposed method was successfully applied for the determination of ET in the real samples

Keywords: Electrochemical sensor; Cyclic voltammetry; Estriol; Detection limit.

* Corresponding author. Tel: +91- 08272228334.

E-mail address: manju1853@gmail.com (J.G. Manjunatha).

1. Introduction

Estriol is one of the four classical ovarian estrogens (estriol, estradiol, estrone, and estetrol), estriol represents a serious influences on reproductive and sexual functioning, the concentrations of which and their changes in humans are closely related to many diseases (12). In aquatic organisms it leads cancer, vitellogenin induction, feminized reproductive organs, reduced fecundity, changes in sex ratio and developmental degeneration. Therefore, developing sensitive, rapid and simple method for the determination of ET is urgent (3-7). Many type analytical methods have been developed to determine the concentrations of ET including chromatographic techniques [8-11], immunoassays [12, 13], UFLC-ffuorescence [14] electrophoresis [15, 16] and electroanalytical methods [17, 18]. Although these methods have been successfully employed, they require long time and lengthy steps for the sample pretreatment. The redox mechanism equations of ET were shown in Scheme 1[19]. The electrochemical techniques are largely used for the determination of electroactive molecules in pharmaceutical forms and physiological fluids due to their easy handling, simplicity and low cost [20-27]. As an electroactive substance, ET has also attracted much interest from electrochemists.

The approach of chemically fabricated modified electrodes in electrochemical determination offers several advantages. They can lower the over potential, increase the reaction rate and sensitivity, improve the selectivity and represents the good LOD [28-33]. Polymer-modified electrodes fabricated by electropolymerization have received wide interest in the detection of biomolecules because of its high selectivity, sensitivity and homogeneity in electrochemical deposition, strong adherence to electrode surface and chemical stability of the films [34, 35]. Protiva Rain Roy et al. [36] has reported Simultaneous electroanalysis of dopamine and ascorbic acid using poly-(N,N-dimethylaniline) modified electrode. Milczarek and Ciszewski reported an electrode modification with polymeric film of 2,2-bis(3-Amino-4-

hydroxyphenyl) hexafluoropropane and studied the electrocatalytic activities toward the oxidation of DA, UA and AA [37].

In our recent studies using PGMCPE, which was planned in our laboratory, satisfactory results were obtained. According to our knowledge no examination has appeared related to the voltammetric determination of ET at PGMCPE in the literature. The aim of this study was to investigate the electrooxidation of ET with various parameters and to test the fate of PGMCPE, for the electroanalysis of ET and to construct a rapid, simple and sensitive method for its determination. 2. Experimental

2.1. Reagents

ET obtained from Tokyo chemical industries company limited (Japan) was used as received. Silicone oil, Glycine, disodium phosphate, monosodium phosphate was obtained from Himedia chemicals, Bangalore, India. Stock solution of ET prepared in ethyl alcohol (25*10" 4 M), Glycine (25*10-3 M) in double distilled water. All other reagents were of analytical grade or equivalent and obtained from Merck. Phosphate buffer solution was prepared by mixing the required amount of 0.2 M monosodium phosphate and 0.2 M disodium phosphate. ET injections containing 10mg/mL were purchased from the local pharmacy. All experiments were carried out at approx. 25OC.

2.2. Apparatus

CV and DPV experiments were carry out using a model EA-201 Chemilink system. A conventional three"electrode system was used with a carbon paste electrode (3 mm diameter CPE), a KCl-saturated calomel reference electrode (SCE), and a Pt wire as the counter electrode. A digital pH meter was utilized for the preparation of the buffer solutions which were used as the supporting electrolyte in CV and DPV experiments.

2.3. Preparation of BCPE

The BCPE was prepared by hand mixing of graphite powder and silicon oil in the ratio of 70:30 (w/w) in an agate mortar until a uniform paste was obtained. The prepared carbon paste was fitting closely packed into a PVC tube (3 mm internal diameter) and the electrical contact was provided by a copper wire connected to the paste at the end of the tube [25].

2.4. Fabrication of PGMCPE:

BCPE was electrochemically fabricated in 1mM Glycine in a PBS solution (pH 5.5) using 10 times cyclic potential sweeps in the range of 500 to 1800 mV at a scan rate of 100mVs-1, as shown in Fig. 1. After electropolymerization, the modified electrode was rinsed thoroughly with distilled water.

3. Results and discussions

3.1. Surface morphology of BCPE and PGMCPE modified electrode

Fig. 1 displays the FESEM images of BCPE (Fig. 3a) and PGMCPE (Fig. 3b). The FESEM image of BCPE shows a rough morphology on the electrode surface. The FESEM of PGMCPE clearly shows that the poly (glycine) is uniformly attached on the electrode surface. 3.1. Optimization of experimental parameters

The experimental results showed that a better conductive polymeric film could be formed when potential scan window was from 500 to 1800 mV. Therefore we selected it for electropolymerisation potential window in this work. In the first scan a broad voltammogram was obtained which goes on decreasing from the second cycle. The gradual decrease of the voltammograms as the number of cycle's increases shows that glycine was deposited on the surface of CPE by electropolymerisation. The number of electropolymerization cycles was

investigated (data not shown), 10 electropolymerization cycles were selected in this work [32].

3.3. Repeatability and long-term stability of the modified electrode

For the application of the sensors, the stability and reproducibility are the powerful features decide the fate of the sensors. To examine the working stability of PGMCPE electrodes, these sensors without renewing the electrode surface were subjected to every 20 min determination of 1*10-4 mol L-1 ET in 0.2 mol L-1 phosphate buffer solutions (pH 6). After 100 min, five PGMCPE retained 95%, when the measurements were completed; the electrodes are stored in the closed vessel. After 15 days, the current response on PGMCPE still remained about 84%, mentioning this electrochemical sensor had the excellent stability. To determine the reproducibility of the sensor, the relative standard deviations of the peak currents are found to be 4.75%, confirming eminent reproducibility. These data show PGMCPE are stable and display reproducible peak current for the sensing of ET.

3.4. Electrochemical behaviors of ET

Cyclic voltammograms of ET at PGMCPE in PBS were shown in Fig 4. In the absence of ET, no peaks were observed at PGMCPE during the cyclic voltammetric measurements within the potential window of 100 mV to 1000 mV. However, upon addition of 1 x 10-4 mol/L ET, a well-defined and sensitive redox peak appears at 542 mV. This parameter indicates, the electrode response was proportional to the oxidation of the electroactive species produced.

3.5 Electrochemical behaviour of ET at PGMCPE and BCPE

The modified electrode was constructed by polymer film attachment. Fig.5 shows the effects of using BCPE and PGMCPE on the electrochemical oxidation of ET based on results from CV. The PGMCPE shows a better sensitivity in comparison to the BCPE. The oxidative peak potential of ET shifted approximately 150 mV towards a negative potential. At BCPE, peak

appeared at 692 mV. At PGMCPE, however, peak observed at 542 mV. The peak currents at the PGMCPE increased by 485% compared to BCPE. The voltammograms showing catalytic oxidation of ET at the PGMCPE.

3.6 Electrocatalytic oxidation of ET by DPV at PGMCPE and BCPE

Fig. 6 shows DPV of ET at a BCPE and at a PGMCPE. At BCPE, ET exhibited a poor electrochemical response, but at the PGMCPE exhibited good response, the peak potential and peak current appears for PGMCPE at 521 mV 10.75 |A respectively. The oxidation current of ET at the PGMCPE was more than that of ET at the BCPE. These results indicated that PGMCPE could accelerate the rate of electron transfer of ET in pH 6, 0.2M PBS.

3.7 The effect of the scan rate on the electrochemical response of ET at PGMCPE

The effect of scan rate on the anodic peak current of ET was studied. As the scan rate increased, the oxidation peak current increased (Fig.7a). The peak current was directly proportional to the scan rate v over the range of 50-200 mVs-1, which suggested a surface-controlled process on the modified electrode surface. The linear regression equation was Ipa (|A) = 0.975 + 0.0799 v (mVs-1) [31], with a correlation coefficient of 0.9989. This result is in good agreement with that in Fig. 7b.

3.5. The influence of pH on the oxidation of ET at the PGMCPE

The effect of varying of pH (5.5-8.0) on the electrochemical responses of the PGMCPE towards the determination of ET was shown in Fig. 8a. It can be seen that the peak current of ET reaches a maximum at pH 6.0, and then decreases gradually with increase of pH value in Fig. 8b. In addition, the solution pH affected the current peak potentials of ET. With pH increasing, their oxidation peak potentials shift to negatively values, showing that protons take part in their electrode reactions. Thus solution pH 6.0 was taken for the determination of ET. Fig.8c shows that the relationship between anodic peak potential (Epa) of ET and pH of PBS solution. It can be found that Epa decreased with the increasing of solution pH. The Epa

is proportional to the pH over the range of 5.5-8. The linear regression equation is Epa (mV) = 808.04-43.14 pH [30], with a correlation coefficient of R = 0.99806.

3.9 Determinatio n of ET

Using a standard addition method, the determination of ET concentration at PGMCPE was using CV. CVs of various concentrations of ET at PGMCPE in 0.2 M PBS at pH 6.0 is shown in Fig. 9. The response of anodic peak currents of ET was proportional to the ET concentrations over a range of 2x10-6 to 1*10-4 M. The linear regression equation obtained is ipa / A = 4.398 + 0.02104 C (M) [30] with a correlation coefficient of 0.9958. The detection limit (3S/M) and limit of quantification (10S/M) were 8.7x10-7 M and 2.6x10-6 M (2x10-6 to 1x10-5 in this range). The comparison of the performance of PGMCPE with previous works was summarized in Table 1. It can be seen that this sensor exhibited higher sensitivity and lower detection limit than most of other sensors reported.

3.10 Analytical Applications

Proposed method was applied to determine ET in ET injections. In our experiments, the concentration of ET was calculated using standard addition method. The relative standard deviation of each sample for five time's parallel detections is less than 4.2%. In addition, the recovered ratio on the basis of this method was investigated and the value is between 96.8 and 102.7%, indicating that determination of ET using PGMCPE is effective and sensitive. 4. Conclusions

This study has indicated that PGMCPE exhibits highly electrocatalytic activity towards the oxidation of ET. The obtained results also showed that PGMCPE has accelerated the electron transfer rate of ET. The results have also indicated that the PGMCPE shows an excellent sensitivity, wide range and low detection limit. Moreover, the sensor has been applied to determination of ET in real samples with satisfactory results. This sensor platform combines easy fabrication and high sensitivity for ET, which has great potential for sensor or biosensor

applications of several analytes in clinical diagnosis, pharmaceutical analysis and in the field

of bio-electrochemistry.

Conflicts of interest

The authors don't have any conflict of interest.

Acknowle dge me nts

We gratefully acknowledge the financial support (Seed money for Young Scientist scheme)

from the VGST, Bangalore under Research Project. No. VGST/SMYSR/2014-15/GRD-

395/2015-16, April 30, 2015 and Mangalore University under Research Project order No.

MU/DEV/2014-15/D3 D.t:30.04.2016

References

[1] P. Gan, R.G. Compton, J.S. Foord, The voltammetry and electroanalysis of some estrogenic compounds at modified diamond electrodes, Electroanalysis 25(2013) 24232434.

[2] T.S. Chen, K.L. Huang, Effect of operating parameters on electrochemical degradation of estriol (E3), Int. J. Electrochem. Sci. 8 (2013) 6343-6353.

[3] Carol Rice, Linda S Birnbaum, James Cogliano, Kathryn Mahaffey, Larry Needham, Walter J Rogan, and Frederick S vom Saal, Environ. Health Perspect. 111 (2003)1683-1690.

[4] T. Colborn, F.S. vom Saal, A.M. Soto, Developmental effects of endocrine-disrupting chemicals in wildlife and humans. Environ, Health Perspect. 101 (1993) 378-384.

[5] S. Jobling M. Nolan, C.R. Tyler, G. Brighty, J.P. Sumpter, Widespread Sexual Disruption in Wild Fish, Environ. Sci. Technol. 32 (1998) 2498-2506.

[6] C. Desbrow, E.J. Routledge, G.C. Brighty, J.P. Sumpter, M. Waldock, Identification of Estrogenic Chemicals in STW Effluent. 1. Chemical Fractionation and in Vitro Biological Screening, Environ. Sci. Technol. 32 (1998) 1549-1558.

[7] N. Hirai, A. Nanba, M. Koshio, T. Kondo, M. Morita, N. Tatarazako, Feminization of Japanese medaka (Oryzias latipes) exposed to 17beta-estradiol: formation of testis-ova and sex-transformation during early-ontogeny, Aquat. Toxicol. 77 (2006) 78-86

[8] S. Studzinska, B. Buszewski, Fast method for the resolution and determination of sex steroids in urine, J. Chromatogr. B: Anal. Technol. Biomed. Life Sci. 927 (2013) 158— 163

[9] N. Tagawa, H. Tsuruta, A. Fujinami, Y. Kobayashi, Simultaneous determination of estriol and estriol 3-sulfate in serum by column-switching semi-micro high-performance liquid chromatography with ultraviolet and electrochemical detection, J. Chromatogr. B. 723 (1999) 39-45.

[10] S. Wang, W. Huang, G. Fang, J. He, Y. Zhang, On-line coupling of solid-phaseextraction to high-performance liquid chromatography for determination of estrogens in environment, Anal. Chim. Acta 606 (2008) 194-201.

[11] Z.L. Li, S. Wang, N.A. Lee, R.D. Allan, I.R. Kennedy, Development of a solid-phase extraction—enzyme-linked immune sorbent assay method for the determination of estrone in water, Anal. Chim. Acta 503 (2004) 171-177.

[12] Y.P. Tang, S.Q. Zhao, Y.S. Wu, J.W. Zhou, M. Li, A direct competitive inhibition time-resolved fuoro immunoassay for the detection of unconjugated estriol inserum of pregnant women, Anal. Methods 5 (2013) 4068-4073.

[13] S.H. Wang, S.L. Lin, L.Y. Du, H.S. Zhuang, Electrochemical enzyme-linked immunoassay for the determination of estriol using methyl red as substrate, Anal. Lett. 39 (2006) 947-956.

[14] N.S. Lisboa, C.S. Fahning, G. Cotrim, J.P. Anjos, J.B. Andrade, V. Hatje, G.O. Rocha, A simple and sensitive UFLC-fuorescence method for endocrine disrupters determination in marine waters, Talanta 117 (2013) 168-175.

[15] A.P. Fonseca, D.L.D. Lima, V.I. Esteves, Degradation by solar radiation ofestrogenic hormones monitored by UV-visible spectroscopy and capillary electrophoresis, Water Air Soil Pollut. 215 (2011) 441-447.

[16] S. Flor, S. Lucangioli, M. Contin, V. Tripodi, Simultaneous determination of nineendogenous steroids in human urine by polymeric-mixed micelle capillary electrophoresis. Electrophoresis 31 (2010) 3305-3313.

[17] K.D. Santos, O.C. Braga, I.C. Vieira, A. Spinelli, Electroanalytical determination of estriol hormone using a boron-doped diamond electrode, Talanta 80 (2009) 1999-2006.

[18] X. Lin, Y. Li, A sensitive determination of estrogens with a Pt nano-clusters/multi-walled carbon nanotubes modified glassy carbon electrode, Biosens. Bioelectron. 22 (2006) 253-259.

[19] Ivana Cesarinoa, H. Fernando, Cincottob, Sergio A.S. Machado, A synergistic combination of reduced graphene oxide and antimonynanoparticles for estriol hormone detection, Sens. Actuators B 210 (2015) 453-459

[20] Hadi Beitollahi, Hassan Karimi-Maleh, Hojatollah Khabazzadeh, Epinephrine in the Presence of norepinephrine using carbon paste electrode modified with carbon nanotubes and novel 2-(4-Oxo-3-phenyl-3,4-dihydro-quinazolinyl)-N'-phenyl-hydrazinecarbothioamide, Anal. Chem. 80 (2008) 9848-9851.

[21] Somayeh Tajik, Mohammad Ali Taher, Hadi Beitollahi, Application of a new ferrocene-derivative modifed-graphene paste electrode for simultaneous determination of isoproterenol, acetaminophen and theophylline, Sens. Actuators B Chem. 197 (2014) 228-236.

[22] Zahra Taleat, Mohammad Mazloum Ardakani, Hossein Naeimi, Hadi Beitollahi, Maryam Nejati, Hamid Reza Zare, Electrochemical behavior of ascorbic acid at a 2,20-[3,6-Dioxa- 1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone carbon paste electrode, Anal. Sci. 24 (2008) 1039-1044.

[23] Mohammad Mehdi Foroughi, Hadi Beitollahi, Somayeh Tajik, Mozhdeh Hamzavi, Hekmat Parvan, Hydroxylamine Electrochemical sensor based on a modified carbon nanotube paste electrode: Application to determination of hydroxylamine in water samples, Int. J. Electrochem. Sci. 9 (2014) 2955 - 2965.

[24] Mohammad Mazloum-Ardakani, Bahram Ganjipour, Hadi Beitollahi, Mohammad Kazem Amini, Fakhradin Mirkhalaf Hossein Naeimi, Maryam Nejati-Barzoki, Simultaneous determination of levodopa, carbidopa and tryptophan using nanostructured electrochemical sensor based on novel hydroquinone and carbon nanotubes: Application to the analysis of some real samples, Electrochim. Acta 56 (2011) 9113-9120.

[25] S. Mohammadi, H. Beitollahi, A. Mohadesi, Electrochemical behaviour of a modified carbon nanotube paste electrode and its application for simultaneous determination of epinephrine, uric acid and folic acid. Sensor Lett. 11 (2013) 388-394.

[26] Hadi Beitollahi, Jahan-Bakhsh Raoof, Hassan Karimi-Maleh, Rahman Hosseinzadeh, Electrochemical behavior of isoproterenol in the presence of uric acid and folic acid at a

carbon paste electrode modified with 2,7-bis(ferrocenyl ethyl)fluoren-9-one and carbon nanotubes, J. Solid State Electr. 16 (2012) 1701-1707.

[27] Mohammad Reza Akhgar, Hadi Beitollahi, Mohammad Salari, Hassan Karimi-Maleh and Hassan Zamani, Fabrication of a sensor for simultaneous determination of norepinephrine, acetaminophen and tryptophan using a modified carbon nanotube paste electrode, Anal. Methods 4 (2012) 259-264.

[28] J.G. Manjunatha, M. Deraman, N. H. Basri, N, S, M. Nor, I. A. Talib, N. Ataollahi, 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 17(2014) 465-476.

[29] J.G. Manjunatha, M. Deraman, N. H. Basri, I. A. Talib, Selective detection of dopamine in the presence of uric acid using polymerized phthalo blue film modified carbon paste electrode, Adv. Mater. Res. 895 (2014) 447-451.

[30] J.G. Manjunatha, M. Deraman, N. H. Basri, I. A. Talib, 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, Arab. J. Chem, (2014) http://dx.doi.org/ 10.1016/j. arabj c.2014.10.009.

[31] J.G. Manjunatha, M. Deraman, N. H. Basri, Electrocatalytic detection of dopamine and uric acid at poly (Basic blue b) modified carbon nanotube paste electrode, Asian J. Pharm.Clin. Res. 8 (2015) 48-53.

[32] J.G. Manjunatha, Poly (Nigrosine) Modified Electrochemical Sensor for the Determination of Dopamine and Uric acid: A Cyclic Voltammetric Study, Int. J. Chem.Tech. Res. 9 (2016) 136-146.

[33] J.G. Manjunatha, A novel poly (glycine) biosensor towards the detection of indigo carmine: A voltammetric study, J. Food. Drug. Anal. (2017) http://dx.doi.org/10.10167j.jfda.2017.05.002.

[34] Y. Ohnuki, T. Ohsaka, H. Matsuda, N. Oyama, Permselectivity of films prepared by electrochemical oxidation of phenol and amino-aromatic compounds, J. Electroanal. Chem. 158 (1983) 55-67.

[35] A. Volkov, G. Tourillon, P.C. Lacaze, J.E. Dubois. Electrochemical polymerization of aromatic amines: IR, XPS and PMT study of thin film formation on a Pt electrode, J. Electroanal. Chem. 115 (1980) 279-291.

[36] Protiva Rain Roy, Takeyoshi Okajima, Takeo Ohsaka. Simultaneous electroanalysis of dopamine and ascorbic acid using poly-(N,N-dimethylaniline) modified electrode, Bioelectrochemistry 59 (2003) 11-19.

[37] G. Milczarek, A. Ciszewski, 2,2-bis(3-amino-4-hydroxyphenyl)hexafuoropropane modified glassy carbon electrodes as selective and sensitive voltammetric sensors, Selective detection of dopamine and uric acid. Electroanalysis 16 (2004) 1977-1983.

[38] P.A. Raymundo-Pereira, A.M. Campos, F.C. Vicentini, B.C. Janegitz, C.D. Mendon9a , L.N. Furini , N.V. Boas, M.L. Calegaro, C.J.L. Constantino, S.A.S. Machado, Jr. Oliveira ON, Sensitive detection of estriol hormone in creek water using a sensor platform based on carbon black and silver nanoparticles, Talanta. 754 (2017) 652-659.

[39] ] H.S. Kushwaha, R. Sao, R. Vaish. Label free selective detection of estriol using graphene oxide-based fluorescence sensor, J. Appl. Phys. 116 (2015) 034701-034701.

[40] Leticia Vieira Jodar, Fabricio Aparecido Santos, Valtencir Zucolotto, Bruno Campos Janegitz, Electrochemical sensor for estriol hormone detection in biological and environmental samples, J. Solid State Electrochem. 8 (2017) 3726-3729.

[41] K.D. Santos, O.C. Braga, I.C. Vieira, A. Spinelli, Electroanalytical determination of estriol hormone using a boron-doped diamond electrode, Talanta. 80 (2010) 1999-2006.

[42] X. Lin, Y. Li, A sensitive determination of estrogens with a Pt nano-clusters/multi-walled carbon nanotubes modified glassy carbon electrode, Biosens. Bioelectron. 22 (2006) 253-259

Figure captions

Fig.1. The scheme of oxidation mechanism of ET.

Fig.2. Continuous 10 cyclic voltammograms for the electrochemical polymerization of 1x10"3 M glycine on a CPE in 0.2M PBS (5.5pH) at the scan rate 50 mV/s.

Fig.3. FESEM images of (a) BCPE (b) PGMCPE

Fig.4. A typical cyclic voltammograms of PGMCPE with ET (1x10-4M) (solid line) in pH 6, 0.2M PBS without 1x10"4 M ET (dashed line) at pH 6, 0.2M PBS.

Fig.5. Cyclic voltammograms of ET (1x10-4M) in 0.2 M phosphate buffer solution of pH 6 at BCPE (solid line) and PGMCPE (dashed line).

Fig.6. DPVs of a solution containing ET (1x10-4M) in 0.2 M PBS (pH 6) at the BCPE, the PGMCPE.

Fig.7. (a) Cyclic voltammograms of ET (1x10-4M) at the PGMCPE in pH 6.5 PBS at various scan rates. From: 50,75, 100,125, 150 and 200 mV/s. (b) Plot of the peak current of ET as a function of the scan rate.

Fig.8. (a) Cyclic voltammograms obtained at the PGMCPE in 0.2 M PBS in pH values, (a) 5.5 (b) 6 (c) 6.5 (d) 7 (e) 7.5 (f) 8 containing ET (1x10-4M) (b) Plot of anodic peak current vs. pH (5.5-8.0) of ET (1x10-4M) at the PGMCPE c. Plot of Epa vs pH for ET.

Fig.9. Calibration plot for the determination of ET at the PGMCPE in pH 6 PBS with the scan rate 50 mV/s.

Table.1 Detection limits and Linear range for determination of ET at some methods

Methods/Electrodes Linear range (mol/L) Detection limits (mol/L) Refere nce

Differential pulse voltammetry 0.2 x 10-6 to 3 x10-6 0.16 x10-6 [38]

fluorescence sensor 1.3 x10-9 [39]

RGO-GNPs-PS/GCE electrodes 1.5 x 10-6 to 22 x10-6 0.48 x 10-6 [40]

Square-wave voltammetry. 2 x 10-7 to 2 x 10-5 1.7 x 10-7 [41]

square-wave voltammetry/ (MWNTs/GCE) 1 x 10-6 to 5 x 10-5 - [42]

Cyclic voltammetry 2x10-6 to 1x10-4 8.7x10-' This work

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Highlights

• Highly sensitive detection of Estriol by cyclic voltammetry.

• A high-performance polymer based biosensor.

• Great applicability towards clinical samples.

• A wide dynamic range, detection limit and remarkably high sensitivity are obtained.