Abstract

Ni²⁺ ion–selective electrode (Ni-ISE) based on plasticized poly(vinyl chloride) (PVC) membrane with 25, 26, 27 tri propoxy 28, Amino 5, 11, 17, 23–tetra–tert–butyl–calix[4]arene as ionophore and dibutyl phthalate (DBP) as plasticizer was designed and constructed. The Ni-ISE showed a linear reply in the concentration range of 1.0 × 10^-1 to 1.0 × 10^-4 M with slope of 29.3 ± 0.5 mV/decad. The Ni-ISE response time was ≤ 6 s and was used for two months with no deviation in the pH range 4 to 9. The best performance was obtained with a membrane composition of 30% PVC, 62% DBP, 3% 25, 26, 27–tripropoxy–28, amino 5, 11, 17, 23–tetra–tert–butyl-calix[4]arene and 5% potassium tetrakis[p–cholorophenyl]borate (KTpClPB). Its detection limit was 1.0 × 10^-5 M. The selectivity coefficients  for different cations were calculated by the matched potential method (MPM). The scanning electron microscopy (SEM) of the Ni-ISE’s membranes showed some morphological changes during its life span, probably due to both the reaction between the Ni²⁺ ion and / or less of the membrane parts by permeation.

Key words: Ni²⁺ ion–selective electrode, 25, 26, 27 tri propoxy 28, amino 5, 11, 17, 23–tetra–tert–butyl–calix[4]arene; scanning electron microscopy (SEM).