Determination of Levodopa Using Biosynthesed Gold Nanoparticles/Multiwalled Carbon Nanotubes/L-Cysteine Composite Film Modified Glassy Carbon Electrode†

doi:10.7503/cjcu20130801

Abstract

Abstract:

Gold nanoparticles were bio-synthesized by the lotus leaf extract. The Au multiwalled carbon nanotubes(MWCNTs)/L-cysteine(L-Cys) composite material was prepared. The electrochemical behavior of levodopa at the modified electrode was studied. In 0.2 mol/L HAc-NaAc(pH=2.6) buffer, levodopa concentration was linear with oxidation peak current in the range of 0.6—40 and 60—120 μmol/L, and the detection limit was 5.2×10^-8 mol/L(S/N=3). The results show that the Au/MWCNTs/L-Cys modified electrode has good stability and high sensitivity. It has a satisfactory result to determine the effective component of real sample with the recovery of standard addition was between 91.2%—102.5%.

Key words: Biosynthesis, Lotus leaf, Multi-walled carbon nanotubes, Levodopa

CLC Number:

O657.1
O646

TrendMD:

YUE Weichao, CAI Zhuo, JIANG Cuiwen, YE Danni. Determination of Levodopa Using Biosynthesed Gold Nanoparticles/Multiwalled Carbon Nanotubes/L-Cysteine Composite Film Modified Glassy Carbon Electrode^†[J]. Chem. J. Chinese Universities, 2014, 35(2): 250.

Figures/Tables 11

Fig.1 FTIR spectra of lotus leaf extracts without(a) and with(b) chloroauric acid

Fig.2 UV-Vis spectrum of the gold nanoparticles

Fig.3 TEM image of the gold nanoparticles

Fig.4 Alterating current impedance spectra of GCE(a), MWCNTs/GCE(b) MWCNTs/L-Cys/GCE(c) and Au/MWCNTs/L-Cys/GCE(d) in 0.10 mol/L KCl containing 5.0×10-3 mol/L Fe(CN)63-/4-(volume ratio 1∶1)Frequency range: 0.001—105 Hz.

Fig.5 Cyclic voltammograms of 8.0×10-5 mol/L levodopa at bare GCE(a), MWCNTs/GCE(b), MWCNTs/L-Cys/GCE(c) and Au/MWCNTs/L-Cys/GCE(d)

Fig.6 CV curves of 1.0×10-4 mol/L levodopa in buffers with different pH valuespH values from a to g: 2.6, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0. Inset shows the effect of pH on peak potential.

Fig.7 Cyclic voltammograms of 1.0×10-4 mol/L levodopa with different scan rates(A), effects of the natural logarithm of scan rate on peak potential(B) and the square root of scan rate on peak current(C)Scan rate(mV·s-1) from a to i: 30, 60, 90, 120, 150, 180, 210, 240, 270.

Fig.8 Differential pulse voltammograms of levodopa with different concentrations(A) and calibration curves of levodopa in the range of 0.6—40 μmol/L(B) and 60—120 μmol/L(C)(A) c(Levodopa)/(μmol·L-1): 0.6, 0.8, 2, 4, 6, 8, 20, 40, 60, 80, 100, 120.

Table 1 Determination of levodopa in tablet

Labelled amount/(mg·table^-1)	Found/(mg·table^-1)
Labelled amount/(mg·table^-1)	Electrochemical method	UV-Vis method
250.0	252.3	256.3
250.0	249.4	254.5
250.0	251.6	253.2
250.0	248.5	255.6
250.0	250.5	253.2
Average value±SD	250.5±1.4	254.9±2.1

Table 2 Recovery of the method

Labelled amount/(μmol·L^-1)	Added/(μmol·L^-1)	Found/(μmol·L^-1)	Recovery(%)	RSD(%)
2.02	2.00	3.99	99.2	4.04
2.02	4.00	6.10	101.3
2.02	6.00	8.22	91.2
2.02	8.00	10.05	102.5
2.02	10.00	12.06	100.3

Fig.9 Reaction mechanism of levodopa at modified electrode

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