| Summary: | Development of the stripping voltammetric method for selective uric acid
analysis through the glassy carbon (GC) and hanging mercury drop (HMD) electrode
coating with molecular imprinting polymer (MIP) has been carried out.
The polymer used as coating was synthesized from methacrylic acid (MAA) as
monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker and uric acid as
template at various molar ratios. The MIP for uric acid was obtained after extraction of
uric acid from the polymer network. The resulted MIP was characterized by Fourier
transform infrared (FTIR), scanning electron microscopy (SEM) and N2 adsorptiondesorption.
The surface of electrode was coated with the polymer to give MIP-coated
electrode at various time and potential. MIP-coated electrode was used as working
electrode in voltammetry to determine uric acid concentration.
Results show that the polymer has been successfully synthesized and the uric
acid has been partially extracted from the framework. SEM images show that the
surface of MIP had pores of �0.1 µm in diameter. The N2 adsorption-desorption data
suggest that there is a small increase in the pore size distribution from 37.71 to 38.02 �
after extraction of the template. The optimal coating potential of MIP on the surface of
GC electrode is at -0.4 V (vs Ag/AgCl) during 60 s. The optimal coating potential and
time of MIP on the HMD electrode are at -1 V (vs Ag/AgCl) and 60 s, respectively. Uric
acid was accumulated on the MIP-coated electrode during 60 s. The polymethacrylic
acid is a non-electrical conducting polymer. Polymer which is synthesized using molar
ratio of MAA, EGDMA, uric acid at 1:3:1 shows the optimum performance as an uric
acid sensor/template. The MIP-coated GC and HMD electrodes have shown their
performance as a sensitive voltammetric sensor for uric acid. The analytical
performance of the method using MIP coated GC electrode are as follow: sensitivity 0.5
µA/nM/cm
2
, limit of detection 4.1x10
-9
M, and recovery of 99.6 %. The MIP-coated
HMD gives the sensitivity of 69.4 µA/nM/cm
2
, detection limit 6.0x10
-10
M and recovery
95.7%. The developed two methods have detection limits 10
4
-10
5
times lower than
spectrophotometric one. The MIP-coated GC and HMD are very selective sensor for
uric acid. The presence of ascorbic acid not significantly interfered on the uric acid
analysis using MIP-coated GC electrode. Using MIP-coated HMD electrode, ascorbic
acid, creatine and creatinine is found not to interfere the uric acid analysis. Analysis of
uric acid in the real samples of serum by this voltammetric method tends to give the
slightly lower results as compared to those done by spectrophotometric method..
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