Determination of thiocyanate ions at nanolevel in real samples using coated graphite electrode based on synthesised macrocyclic Zn(II) complex

The electrode characteristics and selectivities of PVC-based thiocyanate selective polymeric membrane electrode (PME) incorporating the newly synthesized zinc complex of 6,7:14,15-Bzo(2)-10,11-(4-methylbenzene)-[15]-6,8,12,14-tetraene-9,12-N-2-1,5-O-2 (I (1) ) and zinc complex of 6,7:14,15-Bzo(2)-10,11-(4-methylbenzene)-[15]-6,14-diene-9,12-dimethylacrylate-9,12-N-2-1,5-O-2 (I (2) ) are reported here. The best response was observed with the membrane having a composition of I-2:PVC:o-NPOE:HTAB in the ratio of 6:33:59:2 (w/w; milligram). This electrode exhibited Nernstian slope for thiocyanate ions over working concentration range of 4.4 x 10(-7) to 1.0 x 10(-2) mol L-1 with detection limit of 2.2 x 10(-7) mol L-1. The performance of this electrode was compared with coated graphite electrode (CGE), which showed better response characteristics w.r.t Nernstian slope 59.0 +/- 0.2 mV decade(-1) activity, wide concentration range of 8.9 x 10(-8) to 1.0 x 10(-2) mol L-1 and detection limit of 6.7 x 10(-8) mol L-1. The response time for CGE and PME was found to be 8 and 10 s, respectively. The proposed electrode (CGE) was successfully applied to direct determination of thiocyanate in biological and environmental samples and also as indicator electrode in potentiometric titration of SCN- ion.