Development of 2,4-dinitrophenylhydrazine-modified carbon paste electrode for highly sensitive electrochemical sensing of amino acids

Herein, a carbon paste electrode was modified with 2,4-dinitrophenylhydrazine (2,4-DNPHMCPE), for the first time, to sense the three amino acids including glycine, aspartic acid, and glutamic acid. The newly developed 2,4-DNPHCPE presented sensitive electrocatalytic behavior toward amino acids as compared to the unmodified carbon paste electrode under optimized conditions. The maximum value oxidation peak current was obtained at a concentration of 0.6 × 10^–4 M in phosphate buffer saline solution of pH 7.4. The analytical response was achieved for glycine, glutamic acid, and aspartic acid at + 0.8 V, + 0.6 V, + 0.5 V, respectively, at a scan rate of 0.005 V/s. In several scans, the absence of a reduction peak revealed that the mechanism was irreversible. Furthermore, 2,4-DNPHMCPE showed a linear relationship between the amino acids’ concentration and their anodic peak current values range from 0.1 × 10^–4 to 0.6 × 10^–4 M with the limit of detection 0.4 × 10^–5 M (S/N = 3). Optimization of scan rate unveiled that the electrode process was under diffusion control. The involvement of protons and electrons in the amino acids’ oxidation was observed to be equivalent, which in turn proved that the modified electrode possessed good precision and accuracy. In conclusion, the 2,4-DNPHMCPE-based electrochemical sensing method is a low cost and can be used for the sensitive detection of amino acids. Graphic abstract: [Figure not available: see fulltext.]