Highly sensitive SERS detection of tryptophan based on diazo coupling reaction using two derivatization reagents

In this study, a simple, rapid and sensitive tryptophan (Trp) detection method was proposed, which combined surface enhanced Raman spectroscopy (SERS) with diazo coupling reaction and silver dendritic substrate. Two derivatization reagents, 4-mercaptoaniline (PATP) and 2-fluoro-4-mercaptoaniline (2-F-PATP) were used for derivatization reaction with Trp, which can be controlled by experimental parameters such as derivatization reagent concentration and sodium nitrite concentration. The partial least squares quantitative (PLS) detection model is applied in determining the concentration of Trp. The determination coefficient (R 2 ) of PLS model was 0.9617 based on PATP and 0.9950 on 2-F-PATP. The LOD of the two derivatization methods were as low as 10 −11  mol/L. This combined technique has the characteristics of simple operation, high sensitivity and good selectivity, and shows great potential in the detection of Trp in biological media.