An agarose based optical membrane sensor for selective monitoring of trace nickel ions

Abstract

In this paper, a new highly selective optical sensor was prepared by epoxy activation of agarose membrane pieces and chemical immobilization of 1-p-tolyl-3-(3-(trifluoromethyl)phenyl)triaz-1-ene 1-oxide on it. The absorbance variation of immobilized triazene derivative on agarose as a film upon the addition of 1.5 × 10−5 mol L-1 aqueous solutions of Zn2+, Tl+, Al3+, Ca2+, Co2+, CrO42-, Ni2+, Cu2+, H3BO3, Mg2+, Na+, Pb2+, S2O32-, Sn2+, Mn2+, Ce3+, Ag+, Ba2+, Cd2+, Cr3+, Fe3+ and KIO3 revealed substantiality higher changes for the Ni2+ ion compared to other considered ions. Thus, using a triazene derivative as an appropriate ionophore, a selective optical sensor for Ni2+ was prepared by its chemical immobilization on a transparent agarose membrane. The concentration effects of the reagent, pH, and time duration of reaction in immobilizing the ligand were investigated. A distinct change for the absorbance maximum of the ligand was found via contact between the sensing membrane with Ni2+ions at pH = 5.75. For the membrane sensor, a linear relationship was observed between the variance in membrane absorbance (ΔA) at 332 nm and Ni2+ concentrations in a range from 6.28 × 10−5 to 2.80 × 10-10 mol L-1 with a detection limit (3σ) of 1 × 10-10 mol L-1 for Ni2+. The effects of some potentially interfering ions on determining Ni2+ were investigated and no considerable interference was found. The sensor indicated a short response time and decent durability with no reagent leaching trace. The sensor was effectively regenerated by an EDTA solution, and its response was reversible and reproducible with R.S.D. less than 1.7 %. This optode was used to determine Ni2+ in synthetic and environmental water samples.