Analytical and Bioanalytical Chemistry. Electronic Supplementary Material

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1 Analytical and Bioanalytical Chemistry Electronic Supplementary Material Novel sensor based on carbon paste/nafion modified with gold nanoparticles for the determination of glutathione Nada F. Atta, Ahmed Galal, Shereen M. Azab List of Supplements Fig. S1. SEM (15000 x magnification) of CP-electrode, [electrode (1)], [electrode (2)] and CP-electrode (8000 x magnification) Fig. S2. Relation between the anodic and cathodic peak potentials of GSH versus the scan rate at [electrode (2)] Fig. S3A, B. A: Nyquist plots for GSH using [electrode (2)] at two oxidation potentials 110 mv and 275 mv. (Symbols and solid lines represent the experimental measurements and the computer fitting of impedance spectra, respectively. Other experimental conditions can be found in the experimental section). B: Equivalent circuit used for data fitting of the Nyquist plots of figures 4a, 4b, and Fig. S3A Fig. S4. Fig. S5. Comparison of data obtained using [electrode (2)] with the reported literature using gold nanoparticles or Nafion for the determination of GSH Schematic diagrams showing the mechanism of sensing at the modified electrode Fig. S6 A-C. A: Typical impedance spectrum presented in the form of the Nyquist plot for potassium ferricyanide/ferrocyanide using a) bare CP-electrode, b) [Electrode (1)] and c) [Electrode (2)] at the oxidation potential 275 mv. (Symbols and solid lines represent the experimental measurements and the computer fitting of impedance spectra, respectively). B: Equivalent circuit used in the fit procedure of the impedance spectra in A. C: Electrochemical impedance spectroscopy fitting data corresponding to A Fig. S7. DPV of a mixture of 1 x 10-3 M GSH and 1 x 10-3 M Paracetamol (ACOP) in B-R buffer (ph 7.4), scan rate 10 mv/s at [electrode (2)]

2 SEM (CP-electrode) SEM [Electrode (1)] SEM [Electrode (2)] SEM (CP-electrode) (Lower magnification) Fig. S1. SEM (15000 x magnification) of CP-electrode, [electrode (1)], [electrode (2)], and CP-electrode (8000 x magnification)

3 0.14 (C) E/V (vs Ag/AgCl) OX υ (mv/s) Fig. S2. Relation between the anodic and cathodic peak potentials of GSH versus the scan rate at [electrode (2)]. Red

4 Fig.S3A. Nyquist plots for GSH using [electrode (2)] at two oxidation potentials 110 mv and 275 mv. (Symbols and solid lines represent the experimental measurements and the computer fitting of impedance spectra, respectively. Other experimental conditions can be found in the experimental section) Fig. S3B Equivalent circuit used for data fitting of the Nyquist plots of figures 4a, 4b, and Fig. S3A.

5 Fig. S4. Comparison of data obtained using [electrode (2)] with the reported literature using gold nanoparticles or Nafion for the determination of GSH Electrode Detection Sensitivity reference limit Colloidal gold-cysteamine-carbon 0.09 µm 4.2 ± 0.3 naµm 1 1 paste electrode (Au coll -Cyst-CPE) Gold electrode modified with phtalocyanide 5.8 µm 22.4 naµm 1 2 carbon paste elect rode modified 0.3 μm 90.1 μa l/mmol 3 withttf TCNQ complex and Nafion cm 2 Electrode nm µaµm 1 This work [1] L. Agui, C. Pena-Farfal, P. Yanez-Sedeno, J.M. Pingarron, Electrochemical determination of homocysteine at a gold nanoparticle-modified electrode, Talanta 74 (2007) [2] K.I. Ozoemena, T. Nyokong, P. Westbroek, Self-Assembled Monolayers of Cobalt and Iron Phthalocyanine Complexes on Gold Electrodes: Comparative Surface Electrochemistry and Electrocatalytic Interaction with Thiols and Thiocyanate, Electroanalysis 14 (2003) [3] Percy Calvo-Marzal, Karin Y. Chumbimuni-Torres, Nelci Fenalti Höehr, Lauro T. Kubota, Determination of glutathione in hemolysed erythrocyte with amperometric sensor based on TTF-TCNQ, Clinica Chimica Acta 371 (2006) Fig. S5. Schematic diagrams showing the mechanism of sensing at the modified electrode

6 Bare CPE [electrode (1)] [electrode (2)] Z'' (Ω) A Z' (Ω) B Electrochemical impedance spectroscopy fitting data corresponding to Figure A Electrode E/mV Rp Ru C f R f CPE n (kω cm 2 ) (kω cm 2 ) (μfcm 2 ) (kω -1 cm -2 ) (μfcm 2 ) Bare CPE C [Electrode (1)] [Electrode (2)] Fig. S6 A-C. A: Typical impedance spectrum presented in the form of the Nyquist plot for potassium ferricyanide/ferrocyanide using a) bare CP-electrode, b) [Electrode (1)] and c) [Electrode (2)] at the oxidation potential 275 mv. (Symbols and solid lines represent the experimental measurements and the computer fitting of impedance spectra, respectively). B: Equivalent circuit used in the fit procedure of the impedance spectra in A. C: Electrochemical impedance spectroscopy fitting data corresponding to A

7 20 15 GSH ACOP 10 I /µα E/V (vs Ag/AgCl) Fig. S7. DPV of a mixture of 1 x 10-3 M GSH and 1 x 10-3 M Paracetamol (ACOP) in B-R buffer (ph 7.4), scan rate 10 mv/s at [electrode (2)]