Voltammetric enzyme sensor for urea using mercaptohydroquinone-modified gold electrode as the base transducer.
A voltammetric urea-sensing electrode was prepared by combining a lipid-attached urease layer with a 2,5-dihydroxythiophenol-modified gold electrode. A self-assembled monolayer of dihydroxythiophenol was prepared on the gold surface by soaking the electrode into an ethanolic solution containing the modifier. A layer of the lipid-attached enzyme and that of acetyl cellulose overcoat were successively made on the dihydroxythiophenol-modified electrode by applying a dip-coating procedure. The addition of urea in a test solution (10 mM phosphate buffer, pH 7.0) brought about an increase of pH near the urease layer. The pH shift accompanied a negative shift of the anodic peak, which corresponded to the electro-oxidation of dihydroxyphenol moiety to form quinone, on the linear sweep voltammograms for the urease/dihydroxythiophenol electrode. The concentration of urea (0.2-5 mM) could be determined by measuring the electrode current at -0.05 V versus Ag/AgCl from the voltammogram. The electrode was applied to the determination of urea in human urine; the measurement of electrode current at such a low potential provided the urea determination without any electrochemical interference from L-ascorbic acid and uric acid.
Mizutani
F
F
National Institute of Bioscience and Human-Technology, Ibaraki, Japan.
Yabuki
S
S
Sato
Y
Y
D015374:Biosensing Techniques; D004563:Electrochemistry; D004566:Electrodes; D004795:Enzyme Stability; D006046:Gold; D006801:Humans; D006873:Hydroquinones; D016014:Linear Models; D013438:Sulfhydryl Compounds; D014159:Transducers; D014508:Urea / Q000032:analysis* / Q000652:urine; D014510:Urease
D006873:Hydroquinones; D013438:Sulfhydryl Compounds; C056525:1-thio-2,5-dihydroxybenzene; D006046:Gold; D014508:Urea; D014510:Urease