Potassium ion-selective membrane electrodes based on 1,3-alternate calix[4]crown-5-azacrown-5 Sungeun Kim a , Hasuck Kim a, *, Kwan Ho Noh b , Seoung Ho Lee b , Sung Kuk Kim b , Jong Seung Kim c, * a School of Chemistry and Molecular Engineering, Center for Molecular Catalysis, Seoul National University, Seoul 151-742, South Korea b Department of Chemistry, Konyang University, Nonsan 320-711, South Korea c Department of Chemistry, Dankook University, Seoul 140-714, South Korea Received 4 March 2003; received in revised form 23 May 2003; accepted 26 May 2003 Abstract A series of 1,3-alternate calix[4]azacrown ethers for which the monoaza and unsymmetrical crowned-azacrown with different side arms were examined as an ionophore for ion-selective polymeric membrane electrode toward potassium ion. Among them, the electrode based on calix[4]crown-5-azacrown-5 with a phenyl group exhibited near Nernstian response for K  ions over a wide concentration range (1 /10 5 to 1 /10 1 M) with a limit of detection of 2 /10 6 M. It has a fast response time of approximately 2  /3 s and can be used for at least 2 months without observing any major deterioration. Selectivity coefficients indicated that interference from all common alkali, alkaline and transition metal ions was very small. # 2003 Elsevier B.V. All rights reserved. Keywords: Potassium ion-selective electrode; Calix[4]azacrown ether; Potentiometric detection 1. Introduction Ion-selective electrodes (ISE) are the chemical sensors with the longest and probably with the most frequent routine application. Potentiometric detection based on ion-selective electrodes, as a simple method, offers several advantages such as speed and ease of preparation and procedures, simple instrumentation, relatively fast response, wide dynamic range, reasonable selectivity and low cost. Besides, they are ideally suitable for on-site analysis and, nowadays, were found to be applic- able in the analysis of some biologically relevant ions, process control and environmental analysis [1  /4]. As one of the sensing materials, calix[4]ar- enes are readily amenable to chemical modifica- tion at the phenolic hydroxyl groups leading to molecules with selective host-guest chemistry [5,6]. In order to obtain specifically aimed properties, a number of moieties have been attached to the calixarene framework to achieve precise molecular * Corresponding authors. Tel.:  /82-27-99-1351; fax:  /82- 27-97-3277 (J.S. Kim). E-mail addresses: hasuckim@plaza.snu.ac.kr (H. Kim), jongskim@dankook.ac.kr (J.S. Kim). Talanta 61 (2003) 709  /716 www.elsevier.com/locate/talanta 0039-9140/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0039-9140(03)00329-1