PVC-based Mn(III) porphyrin membrane coated graphite electrode for determination of histidine

The construction, performance characteristics, and application of a polymer ic membrane coated on a graphite electrode with unique selectivity toward h istidine are reported. The electrode was prepared by incorporating chloro(5 ,10,15,20-tetraphenylporphyrinato) manganese(III) [Mn(TPP)Cl] into a plasti cized poly(vinyl chloride) membrane. The influences of membrane composition , pH, and foreign ions were investigated. Calibration plots with near Nerns tian slopes for histidine were observed, -55.4 mV/decade, over a linear ran ge of four decades of concentration (1 x 10(-5) to 1 x 10(-1) M). The elect rode has a detection limit of 5 x 10(-6) M histidine and shows a fast respo nse time of about 1 min. The electrode shows high selectivities toward hist idine over several amino acids and common inorganic anions.