Electroanalytical determination of lead with ion-exchange polymer modified electrodes: mesoporosity and preconcentration effect

In the last couple of decades, electrode coatings based on proton conducting polymers were extensively adopted in the electroanalytical field for the preparation of modified electrodes to be used as highly performing sensors. These devices offer several advantages: they reduce adsorption phenomena, suppress the inclusion of interfering species, protect the electroactive surface from passivation and fouling, act as pre-concentrating agents towards selected analytes, modify the process kinetics and diffusion yielding to high electroanalytical sensitivity and selectivity [1-2]. In this context, we would like to show some results on the use of sulphonated poly(aryl ether sulphone) (SPAES) [2-3], an innovative polymer in this field, whose properties can be appropriately designed, tailored and used in the preparation of modified electrodes for electroanalytical applications [2]. Since connectivity and morphology of the modifying polymer are critical factors in controlling conductivity, stability, active surface and diffusion mechanism of the modified electrodes, much attention is devoted to the polymer casting conditions on the glassy carbon support. In particular, the effect of the use of different casting solvents (dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethylsulphoxide (DMSO), N-methylpyrrolidone (NMP)) is evaluated and different quantities of sulphonic groups, in terms of ion exchange capacity (IEC), are tested. Each sample is characterized in terms of residual solvent, water contact angle and analyte adsorptive preconcentration capability. The electrochemical performances are investigated by using a positively charged probe molecule (ruthenium(III) hexaammine chloride), while lead ion is chosen to evaluate the electroanalytical features of the polymeric membranes towards a small analyte of environmental interest. In this last case, linear sweep voltammetry with and without the stripping preconcentration step is employed and the best conditions for lead determination are discussed. In particular, the polymeric mesoporous structure obtained in controlled conditions, appears to be the major responsible of a preconcentration effect yielding to higher peak currents and hence increased sensitivities and lower detection limits in sensors applications. Finally, a Principal Component chemometric Analysis is also employed for results rationalization. References [1] G. Inzelt, M. Pineri, J. Schultze, and M. Vorotyntsev, Electrochim. Acta 45 (2000) 2403–2421. [2] L. Falciola, S. Checchia, V. Pifferi, H. Farina, M.A. Ortenzi, V. Sabatini, Electrochim. Acta 194 (2016) 405-412. [3] V. Sabatini, S. Checchia, H. Farina, M. A. Ortenzi, Macromol. Res. 24 (2016) 800-810.