Novel coated-graphite membrane sensor based on N,N′-dimethylcyanodiaza-18-crown-6 for the determination of ultra-trace amounts of lead

A novel selective membrane electrode for determination of ultra-trace amount of lead was prepared. The PVC membrane containing N,N'-dimethylcyanodiaza-18-cown-6 (DMCDA18C6) directly coated on a graphite electrode, exhibits a Nernstian response for Pb2+ ions over a very wide concentration range (from 1.0 x 10(-2) to 1.0 x 10(-7) M) with a limit of detection of 7.0 x 10(-8) M (similar to14.5 ppb). It has a fast response time of similar to10 s and can be used for at least 2 months without any major deviation in potential. The electrode revealed very good selectivity with respect to all common alkali, alkaline earth, transition and heavy metal ions. The proposed sensor was used as an indicator electrode in potentiometric titration of lead ions and in determination of lead in edible oil, human hair and water samples. The proposed sensor was found to be superior to the best Pb2+-selective electrodes reported in terms of detection limit and selectivity coefficient. (C) 2002 Elsevier Science B.V. All rights reserved.