A highly sensitive and selective bulk optode based on benzimidazol derivative as an ionophore and ETH5294 for the determination of ultra trace amount of silver ions

A novel optical chemical sensor (optode) was fabricated for the determination of silver ions. The optical sensor was prepared by incorporating recently synthesized ionophore, 7-(1H-benzimidazol-1-ylmethyl)-5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioxatriaza cyclopentadecine-3,11(4H,12H)-dione, sodium tetraphenyl borate (NaTPB) as an anionic additive, 3-octadecanoylimino-7-(diethylamino)-1,2-benzophenoxazine (ETH5294) as a chromoionophore, and dioctyl phthalate (DOP) as a plasticizer in a poly(vinyl chloride) membrane. The effect of several parameters in determining Ag+ was studied and optimized. The spectrophotometric method (λmax of 660 nm) was used for the determination of Ag+. Under the optimum conditions, the optical sensor has a wide dynamic range of 1.02×10−11 to 8.94×10−5 mol L−1 Ag+ with the detection limit as low as 2.8×10−12 mol L−1. The response time of the sensor was ∼150 s, with a RSD% of 0.4% (for 1.0×10−6 mol L−1, n=7). The optode could be regenerated by 0.2 mol L−1 HCl solution. The interferences of potential interfering ions were studied. It was shown that the new optode was very selective to silver ions and had no significant response to common ions such as Mn2+, Cd2+, Ni2+, Hg2+, and Co2+. It can be claimed that the sensor can specifically detect silver ions. The sensor was successfully applied for the determination of silver ions in different real samples.