Cr(III) ion-selective membrane sensor based on 1,3-Diamino-2-hydroxypropane-N,N,N',N'- tetraacetic acid

A new greatly selective and sensitive PVC membrane sensor has been developed as a Cr(Ill) ion selective electrode, using an ionophore named 1,3-Diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid (DPTA). The sensor displays a linear dynamic range between 7.0 x 10(-7) and 1.0 x 10(-1) M, with a near Nernstian slope of 19.8 +/- 0.3 mV per decade and a detection limit of 2.0 x 10(-7) M. The best performance was obtained with a membrane composition of 32% poly(vinyl chloride), 57.5% nitrophenyl octyl ether, 3% sodium tetraphenyl borate and 7.5% DPTA. The potentiometric response 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.