New flow injection potentiometric graphite coated ion-selective electrode for the determination of VO2+ ions

A new coated ion-selective electrode for the determination of trace vanadyl ions (VO 2+ ) by flow injection potentiometry (FIP) with a home-made flow cell has been developed. The PVC-based membrane was coated on a graphite electrode with an effective area of 4.90 mm 2 . The optimum membrane contains 5 wt.% 1,8-diaminonaphtalene as ionophore, 35 wt.% plasticizer 2-nitrophenyl octyl ether, 55 wt.% PVC and 5 wt.% additive potassium tetrakis ( p -chlorophenyl) borate. The electrode in flow injection potentiometry resulted in well defined peaks for vanadyl ions with a very high sampling rate (180 injections/h). Linear calibration was obtained from 1.14×10 −7 to 1.14×10 −1 M vanadyl ions, with a slope of 28.3±0.3 mV per decade change in vanadyl concentration, and very low detection limit of 1.14×10 −7 M and the electrode can be used for at least 1 months without any considerable change in potential response. Selectivity coefficients for several ions were obtained by the matched potential method with respect VO 2+ ions. The flow cell is simple to construct and free from memory effect problems over long periods of use. The sensor was used for the recovery of trace VO 2+ ions from tap water and the determination of VO 2+ in synthetic sample.