An electrochemical sensing device with a plasticized polyvinyl chloride (PVC) membrane electrode based on a porphyrin derivative of p-amino tetraphenyl porphyrin (p-NH2TPP) for mercury ion (Hg2+) has been fabricated. The p-NH2TPP based PVC membrane electrode exhibited a nice linear potential performance for responding to Hg2+ in the range of 1.0×10-8 ∼1.0×10-3 mol/L with a slope of 27.54 mV/-pC (25°C) in citrate buffer solution (pH=2.5). The detection limit was evaluated to be 7.5×10-9 mol/L. No obvious interferences were observed from Na+, K+, Ba2+, Mg2+, Ca2+, and C...