Highly selective and sensitive determination of copper ion by two novel optical sensors

New optical sensors for the determination of copper ion by incorporation of 1,1′-(4-nitro-1,2-phenylene)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-lidene)dinaphthalen-2-ol(L1), 1,1′-2,2′-(1,2-phenylene)bis(ethene-2,1-diyl)dinaphthalen-2-ol 1(L2), dibutylphthalate (DBP) and sodium tetraphenylborate (Na-TPB) to the plasticized polyvinyl chloride matrices were prepared. The tendency of both ionophores (L2 and L1) as chromoionophore was significantly enhanced by the addition of DBP to the membrane. The proposed sensors benefit from advantages such as high stability, reproducibility and relatively long lifetime, good selectivity for Cu2+ ion determination over a large number of alkali, alkaline earth, transition and heavy metal ions. At optimum values of membrane compositions and experimental conditions, both sensors' response was linear over a concentration range of 7.98 × 10−6 to 1.31 × 10−4mol L−1 and 1.99 × 10−6 to 5.12 × 10−5 mol L−1 for L2 and L1, respectively. Sensor detection limit based on the definition that the concentration of the sample leads to a signal equal to the blank signal plus three times of its standard deviation was found to be 3.99 × 10−7 and 5.88 × 10−7 mol L−1 for L2 and L1, respectively. The response time of the optodes (defined as the time required reaching the 90% of the peak signal) was found to be 5-8 min for L2 and 20-25 min for L1 based sensor. The proposed optical sensors were applied successfully for the determination of Cu2+ ion content in water samples.