Preparation and characterization of polymer inclusion membrane based optode for determination of Al³⁺ ion

The use of a polymer inclusion membrane (PIM) as a sensing material is a new approach to overcome the selectivity and stability drawbacks of the optical chemical sensor (optode). In this study, non-plasticized PIM containing poly(vinyl chloride) as a support base, sodium morin-5-sulfonate (NaMSA) as a reagent and Aliquat 336 as a fixed carrier (ionophore) was prepared and its performance was tested for application in an optode to determine Al³⁺ ions. The results showed that PIM properties are greatly influenced by the membrane composition. The studies revealed that the optode response was dependent on film thickness, the presence of plasticizer, stirring effect, concentration of NaMSA, concentration of Aliquat 336 and pH of the aqueous solution used. The dynamic range of Al³⁺ ions concentration determined using this optode was linear from 5.19 × 10^-7 to 6.00 × 10^-5 mol L^-1 and the calculated limit of detection (L.O.D.) was found to be 4.07 × 10^-7 mol L^-1. The maximum emission wavelength (λ_em) for the PIM based optode was 512 nm. Scanning electron microscopy analysis of the PIM revealed that a dense texture was formed. Fourier transform infra-red and thermal gravimetry analysis characterizations proved that all of the constituents of the PIM remain within the membrane. The PIM developed in this work was found to be stable, has good mechanical strength, and is sensitive and reusable. Lastly, the PIM was successfully applied as an optical sensor for determination of Al³⁺ ions in an aqueous solution.