PVC membrane and coated graphite potentiometric sensors based on dibenzo-21-crown-7 for selective determination of rubidium ions

Solution studies on the binding properties of dibenzo-21 -crown-7 (DB21 C7) with alkali metal and ammonium ions revealed the occurrence of a selective 1:1 complexation of the ligand with Rb+ ion. Consequently, DB21C7 was used as a suitable ionophore for the preparation of novel polymeric membrane (PME) and coated graphite (CGE) Rb+-selective electrodes. The electrodes exhibit near-Nernstian behavior for Rb+-ions over concentration ranges of 5.0 x 10(-5) to 1.0 x 10(-1) M for PME and 1.0 X 10(-5) to 5.0 x 10(-2) M for CGE with limits of detection of 1.5 x 10(-5) M for PME and 7.1 X 10(-6)M for CGE. The proposed potentiometric sensors possess response times of < 40 s and can be used for at least 7 weeks without observing any deviation. The electrodes revealed comparatively good selectivities with respect to many alkali, alkaline earth, transition, and heavy metal ions. The working pH range of the electrodes is 3.5-8.0.