Electrochemical Determination of Tyrosine and Nitrite Using CS/CMWNTs/GCE-modified Electrode

A novel electrode was successfully made by modifying a glassy carbon electrode (GCE) with a chitosan (CS)/carboxylated multi-walled carbon nanotube (CMWNT) composite. The electrochemical behavior of L-tyrosine (L-Tyr) and nitrite (NO2-) was investigated using cyclic voltammetry, and the detection conditions of L-Tyr and NO2- were explored. The effective area of the CS/CMWNTs/GCE was calculated to be 7.2534 x 10(-6) cm(2). The surface area of the electrode membrane surface increased significantly. Accelerating the electron transfer of K-3[Fe(CN)(6)] is beneficial for the adsorption and enrichment of the measured substance. The results showed that the amperometric response of the sensor reached a maximum when the pH of phosphate-buffered saline (PBS) was 3.6 and 4.7 for L-Tyr and NO2-, respectively. The modified electrode could detect L-Tyr and NO2- in the linear concentration ranges of 1.0 x 10(-8)-2.0 M and 1.5 x 10(-8)-0.3 M, respectively. The detection limits were 1.6 x 10(-9) M and 2.1 x 10(-9) for L-Tyr and NO2-, respectively (S/N = 3). These results demonstrate the high stability and reproducibility of detection, obtained using the CS/CMWNTs/GCE. The modified electrode was applied to determine the L-Tyr content of amino acid injections and the NO2- content of salted radish.