A carbon paste ion selective electrode based on benzo15-crown-5 as an ionophore is proposed for determination of silver in real samples. Important factors such as the amounts of benzo15-crown-5, carbon nanotube as modifier, paraffin as binder and sodium tetraphenylborate (NaTPB) as an additive have been optimized. Under the optimized working conditions: 62.95% (w/w) of graphite powder, 1.80% (w/w) of ionphore, 30.57% (w/w) of paraffin, 30.60% (w/w) of carbon nanotube and 1.08% (w/w) of NaTPB, a nernestian response with a slope of 59.43 (mv) over the concentration range of 10 ² M to 10 ⁵ M was obtained. The limit of detection was calculated to be 10 ⁵ M. The electrode can be used in the pH range of 2-5 and was employed for potentiometric titration of silver with KSCN. The influence of interfering ions was also investigated and the selectivity factors were determined. The proposed electrod was applied for determination of silver in radiographic films.

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