## 2 Materials and Methods
### Apparatus  
The electrochemical measurements were carried out with a PalmSens4 potentiostat (purchased from Thasar Srl, Milan, Italy), controlled by the PSTrace v5.8 software, and connected with an IKA-Topolino magnetic stirrer. The electrochemical cells were composed of a common three-electrode system or screen-printed electrodes. The configuration of the three-electrode system was: a Glassy Carbon Electrode (GCE) with a surface diameter of 3 mm (purchased from ALS Co., Ltd., Tokyo, Japan) as a working electrode; a platinum wire (0.5 mm, surface area \(\sim\)0.7 cm\({}^{2}\)) as a counter electrode, and an RE-1B Ag/AgCl, 3 mol L\({}^{-1}\) KCl (ALS Co., Ltd.), as a reference electrode. The screen-printed electrodes, BTV-SPCEs (model AC1.W4.R1, henceforth SPCE1), and DropSens SPCEs (model C11L, henceforth SPCE2) were purchased from BVT Technologies (Czech Republic) and by Metrohm (Italiana Srl, Origgio (VA), Italy), respectively. The working, the reference, and the auxiliary electrodes are applied on a corundum ceramic base. The working electrode was made of  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Electrode 1** & **Linear Range** & **Detection Limit** & **Reference** \\  & **(umol L\({}^{-1}\))** & **(umol L\({}^{-1}\)/ug L\({}^{-1}\))** & **Reference** \\ \hline GCE-anodic act & 0.01–0.05 & 0.0053/1.6 & This work \\ SPCE-anodic act & 0.067–0.49 & 0.024/7.0 & This work \\ \hline \hline \end{tabular}  
* EPPGE = edge plane pyrolytic graphite electrode; MWCNTs/Cu(OH\({}_{2}\))\({}_{2}\)NP/ILNC/GCE = multiwalled carbon nanotubes/Cu(OH\({}_{2}\)) nanoparticles/ionic liquid nanocomounds (1-ethyl)3-methylimidazolium hexafluorophosphate) modified glassy carbon electrode; VFMCNTPE = vinyl ferrocene modified multiwall carbon nanotubes paste electrode; IMCNT-IL (CCE) = multiwalled carbon nanotube and ionic liquid modified carbon ceramic electrode (MWCNT-IL-CCE). II/CNTPE = 1-butyl-3 -methylimidazolium hexafluorophosphate modified carbon nanotube’s paste electrode; MWCNTs/PCE = multiwalled carbon nanotubes modified pencil graphite electrode; Cu/CTS/MWCNTs/GCE = chitosan-copper complex multivalled carbon nanotubes modified glassy carbon electrode; Silica NPs-CPE = Silica nanoparticles modified carbon paste electrode; SPCE-CCO\({}_{2}\) NP\({}^{-}\) = CeO\({}_{2}\) nanoparticle modified screen-printed carbon electrodes; SPCE/MWCNTs-COOH = screen-printed carbon electrode modified with carboxyl functionalized multivalled carbon nanotubes; G/SPE = graphene nanoribbon modified screen printed electrode; GCE-anodic act = Glassy Carbon Electrode after anodic activation; SPCE-anodic act: screen-printed carbon electrode after anodic activation.  
\end{table}
Table 1: Cont.  
carbon and had a diameter of 1 mm (SPCE1) and 4 mm (SPCE2), the reference electrode was made of Ag/AgCl (mixing ratio 60/40), and the counter electrode was made of carbon (SPCE1) or graphite (SPCE2). The SPEs were connected through a PalmSens SPE connector (purchased from Thasar SrI) with 3 banana receptacles (2 mm) and a connection for the screen-printed electrodes (maximum thickness of 0.5 mm).  
The solution pH was measured by the Metrohm, mod. 713 potentiometer (resolution of \(\pm\)0.1 mV) coupled with a Metrohm combined glass electrode (mod. 6.0259.100), with Ag/AgCl/AgCl/3M KCl internal reference).  
For the characterization of the surface of the SPCEs, the Field Emission Scanning Electron Microscope-FE-SEM-TESCAN (Kohoutovice, Czech Republic) S9000G was used.