Influence of phosphate buffer and proteins on the potentiometric response of a polymeric membrane-based solid-contact Pb(II) ion-selective electrode

摘要

In this work, the influence of phosphate buffer and proteins on the potentiometric response of a polymeric membrane-based solid-contact Pb-selective electrode (Pb-ISE) was studied. The effects of bovine serum albumin (BSA) adsorption at the surface of the ion-selective membrane combined with electrode conditioning in phosphate-buffered saline (PBS) solution was elucidated by potentiometry and electrochemical impedance spectroscopy. The adsorbed BSA at the surface of the Pb-ISE slightly lowered the detection limit but did not influence the selectivity of the Pb-ISE towards the interfering ions studied (Cu, Cd). Conditioning of the Pb-ISE in 0.01 mol dm PBS resulted in a super-Nernstian response which was related to fixation/extraction of Pb in the ion-selective membrane via precipitation of Pb(PO) by PO anions present in PBS. By conditioning of the Pb-ISE in 0.01 mol dm–3 PBS + 1 mg/ml BSA it was possible to extend the linear response range of the Pb-ISE towards lower analyte concentrations. The utilization of this conditioning procedure was validated by determination of Pb concentrations down to ca 20 ppb in aqueous samples by Pb-ISEs and by comparing the results with those obtained by ICP-MS.