Highly sensitive fluorescence optode based on polymer inclusion membranes for determination of Al(III) ions.

This paper reports the use of a polymer inclusion membranes (PIMs) for direct determination of Al(III) ions in natural water by using a fluorescence based optode. The best composition of the PIMs consisted of 60 wt.% (m/m) poly (vinyl chloride) (PVC) as the base polymer, 20 wt.% (m/m) triton X-100 as an extractant, 20 wt.% (m/m) dioctyl phthalate (DOP) as plasticizer and morin as the reagent, was used in this study. The inclusion of triton X-100 was used for enhancing the sorption of Al(III) ions from liquid phase into the membrane phase, thus increasing the optode fluorescence intensity. The optimized optode was characterized by a linear calibration curve in the range from 7.41 × 10(-7) to 1.00 × 10(-4) molL(-1) of Al(III), with a detection limit of 5.19 × 10(-7) molL(-1). The response of the optode was 4 min and reproducible results were obtained for eight different membranes demonstrated good membrane stability. The optode was applied to the determination of Al(III) in natural water samples. The result obtained is comparable to atomic absorption spectrometry method.

Producing "self-plasticizing" ion-selective membranes.

Polymer membranes have been explored for the analysis of ions that do not require plasticizers and with photocurable properties. This work was focused on investigating the viability of the methacrylic-acrylic copolymers as new self-plasticizing membrane matrixes for ion-selective electrodes or other ion-sensor applications. Copolymers with glass transition temperatures ranging from -20 to -44 degrees C could be prepared without added plasticizer and were found to be functional as ion-selective membranes. Both free-radical solution polymerization and photopolymerization could be used, and "self-plasticizing" behavior of copolymers was observed with a high alkylacrylate (R = C4) content. This was found to be compatible with most commercially available ionophores, and sensors for potassium, sodium, calcium and pH were fabricated entirely by photocure procedures; single-step procedures for the immobilization of benzo-15-crown-5 ionophore on these self-plasticizing copolymer matrixes were also developed. Even though the ionophore was immobilized, potentiometric studies revealed that the ionophore remained functional, and thus, these copolymers have the advantage of suffering neither leaching of ionophore nor plasticizers. All these sensors exhibited a Nernstian or near Nernstian response with selectivity comparable to plasticized PVC membranes or other plasticized and photocurable polymer membranes. The long-term response of the potassium sensor with immobilized ionophore and the sodium sensor showed little deterioration for as long as one month and three months, respectively, under continuous use.