RESEARCH ARTICLE Copyright © 2007 American Scientific Publishers All rights reserved Printed in the United States of America SENSOR LETTERS Vol. 5, 1–6, 2007 Cr(III) Ion-Selective Membrane Sensor Based on 1,3-Diamino-2-Hydroxypropane-N,N,N ′ ,N ′ - Tetraacetic Acid Hassan Ali Zamani 1 ∗ , Mohammad Reza Ganjali 2 3 , Mohammad Reza Abedi 1 , and Parviz Norouzi 2 3 1 DepartmentofChemistry,Quchanbranch,IslamicAzadUniversity,Quchan,Iran 2 CenterofExcellenceinElectrochemistry,FacultyofChemistry,UniversityofTehran,Tehran,Iran 3 EcdocrineandMetabolismResearchCenter,TehranUniversityofMedicalSciences,Tehran,Iran (Received: 12 January 2007. Accepted: 23 January 2007) A new greatly selective and sensitive PVC membrane sensor has been developed as a Cr(III) ion selectiveelectrode,usinganionophorenamed1,3-Diamino-2-hydroxypropane-N,N,N ′ ,N ′ -tetraacetic acid (DPTA). The sensor displays a linear dynamic range between 70 × 10 −7 and 10 × 10 −1 M, with a near Nernstian slope of 19.8 ± 0.3 mV per decade and a detection limit of 20 × 10 −7 M. The best performance was obtained with a membrane composition of 32% poly(vinyl chloride), 57.5% nitrophenyloctylether,3%sodiumtetraphenylborateand7.5%DPTA.Thepotentiometricresponse of the proposed electrode is pH independent in the range of 2.5–6.8. The sensor possesses the advantages of short conditioning time, fast response time (<10 s) and, especially, good selectivity towards transition and heavy metal, and some mono, di, and trivalent cations. The electrode can be used for at least 10 weeks without any considerable divergence in the potentials. It was effectively used as an indicator electrode in the potentiometric titration of Cr(III) ions with EDTA and also in the Cr(III) determination in wastewaters of chromium electroplating industries. Keywords: Potentiometry, Cr(III) Sensor, PVC, 1,3-Diamino-2-Hydroxypropane-N,N,N ′ ,N ′ - Tetraacetic Acid. 1. INTRODUCTION Chromium exists in two states; Cr(VI) and hydrated chromium(III) species, despite the Cr trace amounts in the trivalent state. It is known to be an essential element in the human nutrition but its accumulation in the human body results in toxicity. Chromium is widely employed in vari- ous industries such as plating, tanning, paint, and pigment production as well as metallurgy, which possibly contam- inates the environment. Furthermore, chromium in hexavalent state is 100–1000 times more toxic than the other. Chromium(VI) is also reported as mutagenic and carcinogenic for the human body, leading to lung cancer, skin allergy and probably to asthma and renal diseases. As a result, finding an effec- tive method for the chromium determination is of great importance. Consequently, numerous analytical methods have been developed for its determination in different sample ∗ Corresponding author; E-mail: haszamani@yahoo.com matrices such as spectroscopic methods, 1–5 chromato- graphic methods, 6–8 and electrochemical methods. 9–11 Although these methods present high selectivity and sensi- tivity, they tend to be complicated and expensive to apply. There are only a limited number of reports on the develop- ment of highly selective ionophores for chromium(III). 12–25 Recently, several electrodes have been reported for anions and metal ions. 26–35 In this paper, the introduc- tion of a simple and inexpensive method is reported. Particularly, a new Cr 3+ ion-selective membrane elec- trode is employed with the help of 1,3-Diamino-2- hydroxypropane-N,N,N ′ ,N ′ -tetraacetic acid (DPTA) as an neutral ion carrier (Fig. 1). 2. EXPERIMENTAL DETAILS 2.1. Reagent The Merck Co. was the provider for the reagent grades of dibutyl phthalate (DBP), nitrobenzene (NB), ortho-nitrophenyloctyl ether (NPOE), tetrahydrofuran Sensor Lett. 2007, Vol. 5, No. 2 1546-198X/2007/5/001/006 doi:10.1166/sl.2007.209 1