On-line extractive separation in flow injection analysis based on polymer inclusion membranes: a study on membrane...

The effect of temperature on the sensitivity and sampling rate is studied for a flow injection analysis (FIA) system that uses a membrane separation cell fitted with a polymer inclusion membrane (PIM) for the determination of Zn(II). A temperature of 50 °C for the flowing donor and acceptor solutions and the membrane separation cell improves the sensitivity and the sampling rate relative to 20 °C up to 10-fold and 2-fold, respectively. Studies on the stability of the PIM are reported that show a limited loss of the membrane liquid phase into the aqueous phases used in the FIA system but this has exhibited a negligible effect on the amount of Zn(II) transported across the membrane. Most importantly, the extent of leaching of the PIM components is shown to depend on the nature of the aqueous phase with the membrane eventually reaching a stable composition. It is also shown that the application of ultrasound to the membrane separation cell leads to a slight increase in sensitivity without affecting the long term membrane stability.