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.