Mercury(II) ion-selective polymeric membrane sensor based on a recently synthesized Schiff base Mohammad Hossein Mashhadizadeh *, Iran Sheikhshoaie Department of Chemistry, Shahid Bahonar University of Kerman, P.O. Box 133, Kerman 76169, Iran Received 19 September 2002; received in revised form 9 December 2002; accepted 10 January 2003 Abstract A new polyvinyl chloride (PVC) membrane electrode that is highly selective to Hg(II) ions was prepared by using bis[5-((4-nitrophenyl)azo salicylaldehyde)] (BNAS) as a suitable neutral carrier. The sensor exhibits a Nernstian response for mercury ions over a wide concentration range (5.0 /10 2  /7.0 /10 7 M) with a slope of 309 /1 mV per decade. It has a response time of B/10 s and can be used for at least 3 months without any measurable divergence in potential. The electrode can be used in the pH range from 1.0 to 3.5. The proposed sensor shows fairly good discriminating ability towards Hg 2 ion in comparison with some hard and soft metals. The electrode was used in the direct determination of Hg 2 in aqueous solution and as an indicator electrode in potentiometric titration of mercury ions. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Mercury(II)-selective electrode; Schiff’s base; PVC membrane; Potentiometry 1. Introduction Mercury is a poisoning metal; mercury poison- ing causes ill effects on human nervous system and other body systems due to the overexposure of mercury. Today, people are aware of the dangers of mercury, and many of its uses have been prohibited. However, mercury exposure is still an occupational hazard for people in many industries and mercury is present in the environment. Hence, the need for mercury ion determination in clinical analysis and environmental monitoring has led to a number of methods for the measurements of this analyte. The use of ion-selective electrodes is simple and even allows in vivo measurements. A variety of potential ion-carriers has been used in the con- struction of Hg(II)-selective membrane electrodes. Hg(II)-selective electrodes based on chelating reagents as charged carriers were reported repeat- edly. On the other hand, only a few neutral carriers were presented for use in Hg(II) electrodes [1 /7]. The details of some Hg-selective ionophores and electrodes are given in Ref. [1]. In recent years, we have used some thia-sub- stituted crown ethers as neutral carriers in mem- brane transport [8  /10], in solid-phase extraction * Corresponding author. Fax:  /98-341-3222033. E-mail address: mashhadizadeh@mail.uk.ac.ir (M.H. Mashhadizadeh). Talanta 60 (2003) 73  /80 www.elsevier.com/locate/talanta 0039-9140/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0039-9140(03)00036-5