Development of a highly sensitive and selective optical sensor for determination of ultra-trace amount of silver ions

A new selective membrane optical sensor was prepared for the determination of ultra-trace amounts of silver(I). The optical sensor was prepared using a recently synthesized ionophore, 7-(1H-indol-3-ylmethyl)-5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioxatriaza cyclopentadecine 3,11(4H,12H)-dione, as an ionophore and ETH-5294 as a chromoionophore in a PVC membrane. The influence of several parameters on the preparation of the optical sensor and the determination of Ag(I) was studied and optimized. The optical sensor has a wide linear dynamic range (2.27 × 10−11 to 1.13 × 10−3 mol L−1) with a low detection limit of 9.5 pmol L−1 Ag(I). The response time of this sensor was 210 s. The optical sensor could be regenerated several times using 0.2 mol L−1 HCl solution. The influence of potential interference ions on the Ag(I) determination was studied. The results showed that the prepared optical sensor was very selective to silver ions so that it had no significant response to common ions such as Mn2+, Cd2+, Ni2+, Pb2+, Hg2+, and Co2+. The sensor was also applied successfully for the determination of silver ions in different real samples such as Zayandehrood river water, two polymetallic ores, and silver sulfadiazine (1.0%) topical cream.