analytica chimica acta 630 ( 2 0 0 8 ) 57–66 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/aca An efficient and selective flourescent optode membrane based on 7-[(5-chloro-8-hydroxy-7-quinolinyl)methyl]- 5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10- benzodioxatriazacyclopentadecine-3,11(4H,12H)-dione as a novel fluoroionophore for determination of cobalt(II) ions Mojtaba Shamsipur a,∗ , Marzieh Sadeghi a , Kamal Alizadeh b , Hashem Sharghi c , Reza Khalifeh c a Department of Chemistry, Razi University, Kermanshah, Iran b Department of Chemistry, Lorestan University, Khorramabad, Iran c Department of Chemistry, Shiraz University, Shiraz, Iran article info Article history: Received 12 June 2008 Received in revised form 2 September 2008 Accepted 15 September 2008 Published on line 2 October 2008 Keywords: Optode membrane Cobalt(II) Fluoroionophore L Fluorescence quenching abstract A novel fluorescence chemical sensor for the highly sensitive and selective deter- mination of Co 2+ ions in aqueous solutions is prepared. The cobalt sensing system was prepared by incorporating 7-[(5-chloro-8-hydroxy-7-quinolinyl)methyl]-5,6,7,8,9,10- hexahydro-2H-1,13,4,7,10-benzodioxatriazacyclopentadecine-3,11(4H,12H)-dione (L) as a neutral cobalt-selective fluoroionophore in the plasticized PVC membrane containing sodium tetraphenylborate as a liphophilic anionic additive. The response of the sensor is based on the strong selective fluorescence quenching of L by Co 2+ ions. At a pH 5.0, the proposed sensor displays a calibration curve over a wide concentration range of 5.0 × 10 -7 to 2.0 × 10 -2 M with a relatively fast response time of less than 5 min. In addition to high stability and reproducibility, the sensor shows a unique selectivity towards Co 2+ ion with respect to common coexisting cations. The proposed fluorescence optode was successfully applied to the determination of cobalt content of vitamin B12 ampoule, cobalt cake, cobalt alloy and tap water samples. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Compared to ion-selective electrodes, optical sensors based on absorbance or fluorescence have additional feature possi- bilities in that they may take advantage of spectral properties associated with the analyte or analyte specific indication [1–3]. Fluorescent materials are among the mostly used reagents for a variety of sensing applications [4–6]. In fact, in the past two ∗ Corresponding author. Tel.: +98 21 66908032; fax: +98 21 66908030. E-mail address: shamsipur@ics-ir.org (M. Shamsipur). decades, much work has been directed to the development of fluorescent sensors for different metal ions, which offer dis- tinct advantages in terms of sensitivity, selectivity, response time and remote control [6–9]. The theoretical basis of such optical membranes based on plasticized PVC has also been well established [2,10,11]. In developing such fluorescent ionic sensors, in addition to high selectivity towards the ion of interest, a large change in 0003-2670/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2008.09.051