Macrocyclic nickel(II) complex and hydrophilic polyurethane film electrodes for the electrocatalytic oxidation and selective detection of norepinephrine

Macrocyclic Ni(II) complex and hydrophilic polyurethane (PU) were used to modify activated glassy carbon (GC) electrodes for the electrocatalytic oxidation and selective detection of norepinephrine (NE). The Ni(II) complex was electropolymerized using cycling potentials, and the Ni(II) complex-modified electrode had a negatively shifted oxidation potential and increased current in phosphate buffer at pH 7.4. The linear range and detection limit were from 0.10 to 10 muM (390 nA muM(-1), R = 0.999) and 7.7 nM (signal-to-noise ratio, S/N = 3) by amperometry with flow injection, respectively. The Ni(II) complex-modified electrodes were coated with hydrophilic PU for higher selectivity. Hydrophilic anionic PU was produced by the hydrolysis of PU containing gamma-benzyl L-glutamate (PUBLG) segments. The hydrophilic PU-coated electrodes increased the selectivity for NE over ascorbic acid (AA) and uric acid (UA). Moreover, NE in a human urine sample was detected with higher sensitivity, reproducibility, and stability than by using Nation-coated electrodes. Therefore, hydrophilic PU and Ni(II) complex can be used as new electrode materials for the electrocatalysis and selective electroanalysis of NE. In particular, hydrophilic PU can be used as an alternative anionic material to Nafion for better urine compatibility. (C) 2004 Elsevier Ltd. All rights reserved.