A disposable electrochemical sensor based on bifunctional periodic mesoporous organosilica for the determination of lead in drinking waters
A new bifunctional disulfide- and tetrasulfide-bridged periodic mesoporous organosilica (PMO) with mercaptothiazoline ligand was synthesized and employed to prepare chemically modified carbon paste electrodes for Pb(II) detection in aqueous media by square wave adsorptive stripping voltammetry. To demonstrate the real interest of bifunctionalization, carbon paste electrodes were prepared with disulfide- and tetrasulfide-bridged PMO without mercaptothiazoline ligand. Results showed the importance of bifunctionalization of PMOs to improve the sensitivity for the determination of Pb(II) in water samples. To achieve the most accurate and sensitive Pb(II) measurements, optimization of the operating parameters in preconcentration and detection steps was performed. Finally, the modified carbon paste electrode prepared with bifunctional disulfide-bridged PMO with mercaptothiazoline ligand was applied to determine Pb(II) in different water samples without any pre-treatment. Using this electrode, the optimal operating conditions were 120 s of electrolysis time in HCl 0.4 M. In these conditions, the voltammetric signal increased linearly with the preconcentration time from 1 to 10 min. Under optimized conditions, the linear range was 2 - 100 ¿g/L (R2 = 0.9943) with a detection limit of 0.5 ¿g/L (for 5 min preconcentration time). Good reproducibility was achieved on both single and equally prepared electrodes. The accuracy of the method was validated by analysing Pb(II) in different drinking and natural water samples, with spiked recoveries in the range of 95 ¿ 105 ± 10%. The results demonstrated that the prepared electrochemical sensor exhibited selectivity, fast response time and exceptional long-time stability.
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