Optical sensing membrane for determination of trace cadmium(II), zinc(II) and copper(II) based on immobilization of 1-(2-pyridylazo)-2-naphthol on polymer inclusion membrane

Abstract A colour changeable optical sensing membrane was prepared for quantitative detection of Cd(II), Zn(II) and Cu(II) by using polyvinyl chloride membrane containing bis(2-ethylhexyl) phosphate for chemical absorption of chromogenic reagent 1-(2-pyridylazo)-2-naphthol. Under the optimum conditions, the three ions were measured by UV-visible spectrophotometer at λmax=547, 554 and 560 nm, respectively. The linear ranges of 8.90×10-9-8.90×10-4 mol·L-1 [Cd(II)], 1.78×10-9-1.78×10-4 mol·L-1 [Zn(II)] and 1.78×10-7-1.78×10-3 mol·L-1 [Cu(II)] and detection limits of 3.89×10-9, 3.42×10-10 and 1.20×10-7 mol·L-1 were obtained, respectively. The response time was between 7-15 min. For common anions and cations, the sensing membrane exhibited good selectivity. Selective determination of Cd(II), Zn(II) and Cu(II) was achieved by adding a suitable masking agent. The sensing membrane was regenerated by soaking in nitric acid for 1-3 min and maintained a stable response after three times of reuse. The sensing membrane was successfully used for the determination of Cd(II), Zn(II) and Cu(II) in real samples.