A calmagite immobilized agarose membrane optical sensor for selective monitoring of Cu2+

Spectrophotometric studies of 2-hydroxy-1-(2-hydroxy-5-methylphenylazo)-4-naphthalenesulfonic acid (calmagite) complexes with Cu2+, Al3+, Cd2+, Ni2+, Ag+, Pb2+ and Hg2+ ions in acetonitrile solution indicated a substantially larger stability constant for the Cu2+ complex. Consequently, calmagite was used as a suitable ionophore for the preparation of a selective Cu2+ optical sensor, by its immobilization on a transparent agarose film. The effects of pH, reagent concentration and reaction time on the immobilization of calmagite were studied. A linear response curve was observed for the membrane sensor in Cu2+ concentration range of 0.4–200 μg l−1 with an R2 value of 0.997. The detection limit (3σ) of the method for Cu2+ was 0.07 μg l−1. The influence of several potentially interfering ions on the determination of Cu2+ was studied and no significant interference was observed. The sensor showed a good durability and short response time with no evidence of reagent leaching. The sensor was successfully applied for the determination of Cu2+ in environmental water samples.