Chemistry
A Novel Sensor for Uric Acid Based on an Electropolymerization Technique
mol/L. The sensor was used successfully for the determination of uric acid in real samples, with recoveries ranging from 94% to 105%.
Background Uric acid (UA) is the principal final product of purine metabolism in the
human body,1 and Lesch–Nyhan syndrome.2
and is related to many disorders such as gout, hyperuricemia, The detection of UA in physiological samples
using electrochemical techniques has been the subject of extensive inter- est because of its inherent advantages of simplicity, high sensitivity, and relatively low cost compared to conventional colorimetry and spectropho- tometric methodologies.3
As a result, there has been great interest in this
area, leading to the construction of various modified electrodes. Different modified electrodes, including molecularly imprinted polymers4 nanoparticles,5
have been used for the determination of UA.
In this study, a novel MIP-based electrochemical sensor was fabricated by depositing carboxyl-functionalized MWNTs and electropolymerizing poly-o-phenylenediamine (oPD) in the presence of uric acid onto a glassy carbon electrode (GCE) surface. An electroactive substance, potassium fer- ricyanide, was used as the redox probe. Under the optimized conditions, the sensor exhibited good adsorption and high recognition capacity for UA.
Experimental
Chemicals Multiwalled carbon nanotubes were obtained from Shenzhen Nanotech Port Co. Ltd. (Shenzhen, China). Uric acid (UA), dopamine (DA), phen- acetin (PA), ascorbic acid (AA), adrenaline (AD), noradrenaline (NAD), o-phenylenediamine (oPD), and N,N-dimethylformamide (DMF) were purchased from Sigma-Aldrich (St. Louis, MO). All other reagents were of analytical reagent grade or higher, and double-distilled water was used for all solutions.
Preparation of modified glassy carbon electrode (MGCE) The MWNTs (1 g) were treated as reported6
to obtain carboxylic acid-
functionalized MWNTs (MWNTs–COOH). Prior to modification, the surface of the bare GCE was polished with a 0.3- and 0.05-μm alumina–water slurry
Figure 2 – A) Cyclic voltammograms of: curve a) bare GCE, curve b) MGCE, curve c) MIP-MGCE before uric acid removal, curve d) MIP-MGCE. B) Curve e.) MIP-MGCE before UA removal, and curve f) nMIP-MGCE. 1.0 mmol/L [Fe(CN)6
]3– in N2 rate: 50 mV sec–1
-saturated PBS (0.05 M, pH 7.0) containing 0.1 M KCl. Scan .
AMERICAN LABORATORY • 26 • SEPTEMBER 2013 and
molecularly imprinted polymer (MIP) film was fabricated using an electropolymerization technique after depositing carboxyl- functionalized multiwalled carbon nanotubes (MWNTs) onto a glassy carbon electrode surface. The molecularly imprinted sensor was tested by cyclic voltammetry and linear sweep voltammetry. The MIP-based sensor displayed excellent recognition capacity for uric acid compared to other structurally similar molecules. Additionally, the linear sweep voltammetry peak current was linear to the concentration of uric acid in the range from 2 × 10−7 8 × 10−8
A to 8 × 10−5 mol/L, with a detection limit of
in sequence, and thoroughly ultrasonically rinsed with ethanol and doubly distilled water for 5 min. A suspension of MWNTs–COOH (1 mg/mL) in di- methylformamide (DMF) was prepared by the dispersion of MWNTs–COOH using ultrasonic churning. The MWNTs–COOH layer was modified onto the electrode surface using a traditional dropping method. The electrode ob- tained is called the MGCE.
Electrochemical measurements Electrochemical experiments were performed on a CHI 800C workstation (ChenHua Instruments Co., Shanghai, China) with a conventional three- electrode system. Solutions were deaerated (using prepurified nitrogen) for 10 min before the electrochemical experiment.
Results and discussion
Electropolymerization As shown in Figure 1, a broad and irreversible oxidation peak appeared with a peak potential at 0.6 V. The anodic peak current disappeared much more
by Youyuan Peng
Figure 1 – Repetitive cyclic voltammograms during the electropolymer- ization of oPD (5.0 mM) and uric acid (1.0 mM): a) onto bare GCE and b) onto MGCE. Scan rate: 50 mV sec–1
. Supporting electrolyte: N2 PBS (0.05 M, pH 7.0) containing 0.1 M KCl. Scan circles: 20.
-saturated
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