Development of an electrochemical sensor based on Schiff base for Cu(II) determination at nano level in river water and edible materials

Plasticised membranes using 2-[{(2-hydroxyphenyl)imino}methyl]-phenol (L1) and 2-[{(3-hydroxyphenyl)imino}methyl]-phenol (L2), have been prepared and investigated as Cu2+ ion-selective sensors. Effect of various plasticisers, namely, dibutyl phthalate (DBP), dibutyl sebacate (DBS), benzyl acetate (BA), o-nitrophenyloctylether (o-NPOE) and anion excluders, oleic acid (OA) and sodium tetraphenylborate (NaTPB) was studied and improved performance was observed in several instances. Optimum performance was observed with membranes of (L1) having composition L1 : DBS : OA : PVC in the ratio of 6 : 54 : 10 : 30 (w/w, %). The sensor works satisfactorily in the concentration range 3.2 x 10-8-1.0 x 10-1 mol L-1 with a Nernstian slope of 29.5 +/- 0.5 mV decade-1 of acu2+. The detection limit of the proposed sensor is 2.0 x 10-8 mol L-1 (1.27 ng mL-1). Wide pH range (3.0-8.5), fast response time (7 s), sufficient (up to 25% v/v) non-aqueous tolerance and adequate shelf life (3 months) indicate the utility of the proposed sensor. The potentiometric selectivity coefficients as determined by matched potential method indicate selective response for Cu2+ ions over various interfering ions, and therefore could be successfully used for the determination of copper in edible oils, tomato plant material and river water.