Attachment of ρ-aminobenzene sulphonic acid into magnetic Fe3O4 reduced graphene oxide and its application for sensitive determination of L-tryptophan in milk and banana samples

This paper reports the attachment of p-aminobenzene sulfonic acid on the surface of magnetic Fe₃O₄-reduced graphene oxide. Different techniques including FTIR, UV, EIS, XRD, and SEM imaging were employed for characterization. The finding indicates the successful attachment of the p-aminobenzene sulfonic acid to the surface. The synthesized material was used to make a carbon paste electrode for the determination of the essential amino acid L-tryptophan (L-Try). EIS and CV characterization of the electrode further confirms the attachment of the acid. Of the different electrode materials used, the p-aminobenzene sulfonic acid attached magnetic Fe₃O₄ reduced graphene oxide showed very good electrocatalytic activity. The scan rate study showed that the electrode process is an adsorption-controlled one. The prepared electrode material gave a linear curve for 0.001 μM to 10 μM L-Try concentrations, and the limit of detection and limit of quantification were 0.26 nM and 0.78 nM, respectively. Furthermore, the electrode material was employed for the determination of L-Try in a milk and banana sample.