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    Microwave-assisted synthesis of unmodified gold nanoparticles for colorimetric detection of dopamine
    (2017-01-01)
    Detsri, Ekarat
    ;
    Kamhom, Kanrayasiri
    ;
    Detsri, Chatsuda
    Unmodified gold nanoparticles (AuNPs) have been successfully synthesized by the chemical reduction of tetrachloride gold(III) ions ([AuCl<inf>4</inf>]<sup>-</sup>) in the presence of sodium citrate based on the rapid microwave-assisted approach. The diameter of the synthesized nanoparticles was found in the range of 16.50±2.75 nm. The AuNPs were characterized using UV-vis spectrophotometer, zeta potential analyzer and transmission electron microscope (TEM). The sodium citrate protected AuNPs were found to be selective and sensitive for the detection of dopamine. It was based on the aggregation change of the nanoparticles from random coil to hairpin structure upon the addition of dopamine concentration. The red shift of the plasmonic peak wavelength of AuNPs could be used for the detection of dopamine. The response to dopamine allows for a linear range from 10 to 125 mg·L<sup>-1</sup> (R<sup>2</sup> = 0.9804) with a limit of detection (LOD) at a signal to noise ratio of 3 of 12.85±1.38 mg·L<sup>-1</sup>. The colorimetric sensor was evaluated with 98.0-99.9% recovery of added dopamine in urine sample. The proposed sensor was successfully applied to the determination of dopamine in biological samples.
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    Single-wall carbon nanotube modified glassy carbon electrode for electroanalytical determination of dopamine
    (2010-11-29)
    Chuekachang, Sopis
    ;
    Kruefu, Viruntachar
    ;
    Chaiyasit, Suwan
    ;
    Phanichphant, Sukon
    In this research, a glassy carbon electrode modified with single-wall carbon nanotubes for electrochemical determination of dopamine was studied by cyclicvoltammetry (CV) and differential pulse voltammetry (DPV). The oxidation and reduction potentials of dopamine using voltammetric technique were measured. The SWCNTs/GC 10 μL was used to test the linearity of anodic oxidation of dopamine by DPV. The peak current increased linearly with concentration of dopamine in the range of 2.5-25 ppm (R<sup>2</sup>=0.9766).For the life time of the SWCNTs/GC, the cut-off criterion of the DPV was detected in the reduction of current by 50 %. The lifetime of the SWCNTsmodified depended on the oxidation of dopamine because of fouling of the electrode surface due to the adsorption of oxidation products. 34 repetition cycles was obtained. The detection limit of the dopamine as obtained from the oxidation current in DPV was 0.021 ppm (S/N=3) with minimum current for the detection of dopamine of 0.033 μA. The reproducibility of electrocatalytical studies was better within 90% (10% RSD). The relative standard deviation (RSD) of 8.42% for 100 ppm dopamine (n=20) showed excellent reproducibility. Drug samples obtained from Radvitee hospital were tested as the mentioned procedure. The percentage recovery of dopamine in drug samples was 120. ©2010 IEEE.