Synthesis of 3-((6-methyl-5-oxo-3-thioxo-2,5-dihydro-1,2,4-triazin-4(3H)-yl)imino)indolin-2-one as an Excellent Ionophore to the Construction of a Potentiometric Membrane Sensor for Rapid Determination of Zinc

3-((6-methyl-5-oxo-3-thioxo-2,5-dihydro-1,2,4-triazin-4(3H)-yl)imino)indolin-2-one was used as a neutral ion carrier in the PVC membrane to construction of a new zinc ion selective electrode. The sensor shows a good Nernstian response for Zn2+ over a wide concentration range of 1.0×10-5 to 1.0×10-1 mol L-1 with a slope of 27.12 mV per decade. The limit of detection of the sensor is 8×10-6 mol L-1. The sensor has a relatively fast response time (~5 s) and a useful working pH range of 4.4-8.0 and it can be used without any divergence in Nernstian response for 60 days with high reproducibility. Interference of some cations was also evaluated and it exhibits an appropriate selectivity. Finally it was used as an indicator electrode in potentiometric titration of Zn2+ with EDTA and in direct determination of Zn2+ in rice and in zinc enriched soufflé cake samples. The results indicate that this electrode is sensitive for determination of Zn2+ ion.