Direct determination of aluminium in foods and pharmaceutical preparations by potentiometry using an AlMCM-41 modified polymeric membrane sensor

Abstract

A potentiometric aluminium sensor, based on the use AlMCM-41 as a neutral carrier, in poly(vinyl chloride) (PVC) matrix, is reported. The sensor exhibits significantly enhanced selectivity toward Al 3+ ions over the concentration range 1.0 × 10 −7 to 1.0 × 10 −1 M with a detection limit of 8.6 × 10 −8 M and a Nernstian slope of 19.5 ± 0.4 mV/decade of activity. The best performance was obtained with membrane composition 30% poly(vinyl chloride), 67% acetophenone, 3% ionophore and 2 mL tetrahydrofuran. Fast and stable response, good reproducibility and long-term stability are demonstrated. The response time of the sensor is ∼10 s and membrane could be used over a period of 3 months without any considerable divergence in potentials. Selectivity coefficients were determined by matched potential method (MPM). The AlMCM-41-based sensor is suitable for use in aqueous solution of pH 3–6. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode. It was used to determine Al 3+ in drugs and food products.