High sensitive optode for selective determination of Ni 2+ based on the covalently immobilized thionine in agarose membrane

Abstract

A novel Ni 2+ optode was prepared by covalent immobilization of thionine, 3,7-diamine-5-phenothiazoniom thionineacetate, in a transparent agarose membrane. Influences of various experimental parameters on Ni 2+ sensing, including the reaction time, the solution pH and the concentration of reagents were investigated. Under the optimized conditions, a linear response was obtained for Ni 2+ concentrations ranging from 1.00 × 10 −10 to 1.00 × 10 −7 mol l −1 with an R 2 value of 0.9985. The detection limit (3 σ) of the method for Ni 2+ was 9.30 × 10 −11 mol l −1. The influence of several potentially interfering ions such as Ag +, Hg 2+, Cd 2+, Zn 2+, Pb 2+, Cu 2+, Mn 2+, Co 3+, Cr 3+, Al 3+ and Fe 3+ on the determination of Ni 2+ was studied and no significant interference was observed. The membrane showed a good durability and short response time with no evidence of reagent leaching. The membrane was successfully applied for the determination of Ni 2+ in environmental water samples.