Feature Article Cobalt(II)-Selective Coated Graphite PVC-Membrane Electrode Based on a Recently Synthesized Dibenzopyridino-Substituted Macrocyclic Diamide Mojtaba Shamsipur a ,* Shohre Rouhani b , Tahereh Poursaberi c , Mohammad Reza Ganjali c , Hashem Sharghi d ,and Khodabakhsh Niknam d a Departments of Chemisty, Razi University, Kermanshah, Iran; e-mail: mshamsipur@yahoo.com b Center of Color Research, Tehran, Iran c Department of Chemistry, Tehran University, Tehran, Iran d Department of Chemistry, Shiraz University, Shiraz, Iran Received: July26, 2001 Final version: October11, 2001 Abstract Acobalt(II)-selectivegraphitecoatedPVC-membraneelectrodehasbeendevelopedbyusinganewdibenzopyridino- substitutedmacrocyclicdiamideasaneutralcarrier.TheelectrodeexhibitsaNernstianresponseforCo 2 ionsovera verywideconcentrationrange(7.0  10 7  1.0  10 2 M).Thelimitofdetectionwas2.0  10 7 M(ca.12ppb).Ithasa fastresponsetimeofabout10sandcanbeusedforatleast3monthswithoutobservinganydeviation.Theproposed electroderevealedgoodselectivitiesforCo 2 overawidevarietyofalkali,alkalineearth,transitionandheavymetal ions, and could be used in a pH range of 3.0±8.5. It has been used as an indicator electrode in the potentiometric titration of Co 2 ions and in direct determination of cobalt ion in waste water samples. Keywords: Cobalt ion-selective electrode, Coated graphite, PVC-membrane, Macrocyclic diamide, Potentiometry 1. Introduction Potentiometricdetectionbasedonion-selectivesensors,asa simpleandreliablemethods,offersgreatadvantagessuchas speed, ease of preparation, wide dynamic range, and low cost [1]. Especially, potentiometric sensors prepared by coatingpolymericfilmscontainingelectroactivespecieson metallicorgraphiteconductorsofanyconvenientgeometric size and shape (i.e. wire, disk, cylinder, thin film, etc) are shown to be very effective for the selective detection of a widevarietyoforganicandinorganiccationsandanions[2± 6].Althoughtherelevantprocessesthatoccuratmembrane- solid contact interfaces are still not fully understood, electrodesofthistypehavebecomequitepopular,because they are very simple, durable, inexpensive, and capable of reliableresponseinawideconcentrationrange[1,3].These typeofelectrodeshaveamuchhighermechanicalresistance so they have been used as potentiometric detector in capillaryelectrophoresis[3,7]. Inthepastfewdecades,considerableeffortshaveledto the development of selective sensors for alkali, alkaline earth, transition and heavey metal ions [8]. Among tran- sitionmetals,cobalt(II)hasreceivedlessattentioninspiteof its wide spread occurance in meteorites, sea-and fresh waters,soils,plants,andanimals[9].However,despitethe urgent need for Co 2 -selective sensors for potentiometric monitoringofCo 2 ioninvarioussamples,therehavebeen onlylimitedreportsofcobaltion-selectiveelectrodesinthe literature[10±15].Moreover,mostoftheseelectrodeshave narrow working concentration ranges (some 1.0  10 5  1.0  10 1 M), near or non-Nernstian response, long re- sponse times, and they suffer from serious interferences fromvariousionssuchasNi 2 ,Fe 3 andNa  . Wehavebeenrecentlyinvolvedinpreparationofnewion- selective electrodes for some metal ions such as Ag  [16], Pb 2 [17±22],Zn 2 [23],Cu 2 m[24,25],Hg 2 [26,27],Ni 2 [28], Cd 2 [29], Be 2 [30], Sr 2 [31] and Ce 3 [32] using differentnon-cyclicandmacrocyclicneutralionophores.In this work, we report the first synthesis and use of 9-tert- butyl-3,9,15,21-tetraaza-4,5;13,14-dibenzo-6,12-dioxabicy- clo[15.3.1]henicosa-1(21),17,19-triene-2,16-dione (I, Scheme1)asanexcellentneutralioncarrierinconstruction of a highly selective Co 2 coated graphite membrane electrode. Scheme1. 729 Electroanalysis 2002,14,No.11 ¹WILEY-VCH Verlag GmbH, 69469 Weinheim, Germany, 2002 1040-0397/02/1106-0729 $ 17.50+.50/0