Voltammetric quantification of tryptophan using a MWCNT modified GCE decorated with electrochemically produced nanoparticles of nickel

摘要

A selective quantification of tryptophan (TRP) in the presence of ascorbic acid (AA) was carried out using a voltammetric nanosensor prepared by modifying a glassy carbon electrode (GCE) modified with composite of nanoparticles of nickel (NiNPs) and multi-walled carbon nanotubes (MWCNTs). The nickel nanoparticles were obtained by sweepings from -1.5V to 1.5V for 20 cycles by immersing the MWCNTs modified GCE into 0.1 M Kd solution containing 10mM nickel (Ⅱ) chloride. Energy dispersive X-ray and scanning electron microscopic techniques were utilized for characterizing the electrode layer. Compared with a naked GCE and a GCE modified with carbon nanotubes, the proposed electrode (NiNPs-MWCNTs/GCE) presented a high electrocatalytic effect for the electrode process of both TRP and AA and remarkably enhanced their voltammetric signals. The separation of peak potentials between AA and TRP was large enough to enable the simultaneous quantification. The current response showed linear dependence on the concentrations of TRP in the range of 2.0 × 10~(-8)-6.5 × 10~(-6)M (R~2 = 0.9989) with a detection limit of 6.6 × 10~(-9) M. The quantification of tryptophan (TRP) in cow's milk has successfully been carried out using the proposed electrode.