Determination of Tryptophan using ap-Sulfonated Calix [4,6,8]arene Modified Gold Electrode

Abstract

The ability of p-sulfonated calix[n]arenes (n ¼ 4, 6, 8) to form complexes with tryptophan was studied. The electrochemical properties of these complexes immobilized on gold surfaces were examined by cyclic voltammetry. Parameters affecting the performance of the modified electrodes including the arene concentration, scan rate, applied potential, and pH were optimized. Under the optimal conditions, the method had a linear response to tryptophan between 1 Â 10 À7 M and 1 Â 10 À5 M with a detection limit of 3 Â 10 À8 M. The interaction of the tryptophan-p-sulfonated calix[4]arene complex was more stable than the tryptophanp-sulfonated calix[6]arene and p-sulfonated calix[8]arene complexes. Molecular modeling calculations indicated that electrostatic interactions and structural matching effects were predominant stabilizing factors. The modified electrodes demonstrated good reproducibility and high selectivity, illustrating their effectiveness for analytical measurements.

Supramolecular p-sulfonated calix[4,6,8]arene for tryptophan detection

“…This may be attributed to the interaction between the -NH 2 + of tryptophan and the -SO 3 -of calixarene, and the cavity size of SC4A may be more appropriate for tryptophan than SC6A and SC8A. This finding was consistent with the trend observed in molecular modeling calculation results, 45 as shown in Fig. 10.…”

“…To make a distinct comparison with previous literature reported methods, the characteristics of different electrochemical sensors for tryptophan are shown in Table 1. [37][38][39][40][41][42][43][44][45][46] This indicated that the SC4A and cysteamine modified gold electrode was an appropriate platform for the electrochemical determination of tryptophan and had higher sensitivity to tryptophan (Table 1). Figure 9 shows that SC4A had the highest interaction with tryptophan in three SCnA (n = 4, 6, 8).…”