Preparation Of Carbon Nanotubes Modified Electrode And Its Application In The Detection Of Amino Acids

Carbon nanotubes are being more and more concerned because of their huge surfaceareas, excellent catalytic capability and fast electron transfer rate.When carbon nanotubes areused as modifiers for the study of chemically modified electrodes, the detection sensitivityand the selectivity could be improved, the detection limit could be lowered, the test rangecould be expanded. In the work, three kinds of modified electrodes based on carbonnanotubes were prepared, and used for detection of amino acids, the details are listed below:(1) A multi-walled carbon nanotubes-Nafion modified glass carbon electrode (MWNTs-Nafion/GCE) was developed by drop coating method. Based on the modified electrode, a novelelectrochemical determination method of tryptophan in fermented liquids was established. Theresult shows that the MWNTs-Nafion/GCE electrode exhibits good electrocatalytic activity totryptophan. With pH4.0phosphate buffer solution as supporting electrolyte, at1.01V, theoxidation peak currents of tryptophan are in good proportion to the concentrations oftryptophan. The corresponding linear equation is Ip(μA)=2.432×104C (mol L-1)+3.1452,R2=0.9973, the linear range of tryptophan concentration is from5.0×10-7to2.0×10-4mol L-1,the detection limit is2.7×10-8mol L-1(S/N=3). This method can be successfully applied to thedetection of tryptophan in fermented liquids, the recovery is within98.3%~104.3%,RSD≤3.0%. The selectivity and sensitivity of this method are satisfactory, the operation is facileand the results are stable.(2) A novel copper oxide nanoparticles and multi-walled carbon nanotubes modifiedglass carbon electrode (CuO/MWNTs/GCE) was prepared by electrochemical depositionmethod. The electrochemical characteristics of tyrosine at this modified electrode werestudied by cyclic voltammetry and linear sweep voltammetry. The result shows that anoxidation peak of tyrosine is at0.645V in pH8.0of phosphate buffer solution at theCuO/MWNTs/GCE. The oxidation peak currents of tyrosine are in good proportion to theconcentrations of tyrosine in the range of2.0×10-7~2.0×10-4mol L-1, the linear regressionequation is: Ip(μA)=2.0455+0.1072×105C (mol L-1), R2=0.9996, the detection limit is9.6×10-9mol L-1. The proposed method has been sucessfully applied to determine tyrosine inhuman urine, the recovery is within98.86%~110.00%. The method has good sensitivity,selectivity and practicality.(3) The cuprous oxide and multi-walled carbon nanotubes modified glass carbonelectrode (Cu2O-MWNTs/GCE) was developed by drop coating method, the electrochemicalbehavior of glucosaminic acid at this modified electrode was studied. The result shows thatthe Cu2O-MWNTs/GCE shows excellent electrocatalytical activity to glucosaminic acid, anoxidation peak of glucosaminic acid is at0.80V in pH6.0of phosphate buffer solution at the Cu2O-MWNTs/GCE. The oxidation peak currents are in proportionto the concentrations of glucosaminic acid in the range of1.0×10-5~1.0×10-3mol L-1,the corresponding linear equation is Ip(μA)=0.5179×104C (mol L-1)+1.4923, R2=0.985, witha detection limit of2×10-6mol L-1(S/N=3), the recovery is within93.3%~103.5%.