Novel coated graphite electrode for the selective determination of Gd(III) in rocks and waste water samples

A novel gadolinium selective coated graphite electrode based on 2,6-bis-[1-{N-cyanopropyl,N-(2-methylpridyl)}aminoethyl]pyridine [P] is described. The best performance was exhibited by the electrode having membrane composition P:NaTPB:PVC:NPOE as 8:4:30:58 (%, w/w). The electrode demonstrates excellent potentiometric characteristics towards gadolinium ion over several interfering ions. The electrode exhibited a Nernstian response to Gd3+ ion over a wide concentration range 2.8 x 10(-7) to 5.0 x 10(-2) M with a detection limit(6.3 +/- 0.1) x 10(-8) M and slope 19.6 +/- 0.1 mV decade(-1) of a(Gd3+). Furthermore, it showed a fast response time (12 s) and can be used for 2.5 months without significant divergence in its characteristics. Noticeably, the electrode can tolerate the concentration of different surfactants up to 1.0 x 10(-4) M and can be used successfully in 30% (v/v) ethanol media and 10% (v/v) methanol and acetonitrile water mixture. The useful pH range of this sensor is 2.0 to 8.0. It is sufficiently selective and can be used for the determination of Gd3+ ions in waste water and rock samples. It also serves as a good indicator in the potentiometric titration of GdCl3 with EDTA. (C) 2009 Elsevier Ltd. All rights reserved.