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

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 Al³⁺ 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 Al³⁺ in drugs and food products.