Amperometric determination of epinephrine with an osmium complex and Nafion double-layer membrane modified electrode

The [Os(bpy)₂(PVP)₁₀Cl]Cl polymer and Nafion have been covered on a glassy carbon electrode by drop-coating to fabricate a double-layer membrane modified electrode. The modified electrode showed an excellent electrocatalytical activity for the oxidation of the neurotransmitter epinephrine (EP). Under usual physiological pH conditions, the logarithm of the catalytic current of EP vs. its concentration showed a linear relation in the range of 4.0x10^-9-5.4x10^-6M and 5.4x10^-6-3.1x10^-4M with correlation coefficient of 0.995 and 0.996, respectively. The modified electrode could eliminate efficiently the interference of ascorbic acid, glucose and uric acid at 200-, 8600- and 20-fold concentration of EP (at 5.0x10^-5M), and it has been satisfactorily used for the amperometric determination of EP. The electrocatalytical rate constant k(ch) was evaluated with a rotating disk electrode. Both the presence of a Nafion film and the increase in EP concentration resulted in a decrease of k(ch). The apparent Michaelis-Menten constant is about 0.51mM. The modified electrodes exhibited a good reproducibility, sensitivity and stability for the determination of EP. Copyright (C) 1999 Elsevier Science B.V.