A Novel Potentiometric Sensor for Thiocyanate Based on an Amide‐Linked Manganese Diporphyrin Xanthene

The synthesis of a new compound, amide‐linked manganese diporphyrin xanthene (Mn₂Cl₂ADPX), and its application for preparation of thiocyanate selective electrodes was described. The electrode was prepared with a PVC membrane combining Mn₂Cl₂ADPX as an electro active material, 2‐nitrophenyl octyl ether (o‐NPOE) as a plasticizer in the percentage ratio of 3 : 65 : 32 (Mn₂Cl₂ADPX: o‐NPOE: PVC, w : w : w). The electrode exhibited linear response within the concentration range of 2.4×10^?6 to 1.0×10^?1 M SCN^?, with a working pH range from 3.0 to 8.0 and a fast response time of less than 60 s. Several electroactive materials and solvent mediators have been compared and the experimental conditions were optimized. The Mn₂Cl₂ADPX based electrode shows obviously better response characteristics than that of monoporphyrin manganese in terms of working concentration range and slope. Selectivity coefficients for SCN^? relative to a number of interfering ions were investigated. The electrode exhibits anti‐Hofmeister selectivity toward SCN^? with respect to common coexisting anions. The electrode was applied to the determination of SCN^? in body urine with satisfactory results.