Dynamic-SERS spectroscopy for the in situ discrimination of xanthine analogues in ternary mixture

Nowadays, there is a growing demand for analytical methods capable of providing rapid and simple identification of certain compounds in complex samples without a time-consuming separation process. In this report, a combinative strategy of dynamic surface-enhanced Raman scattering (DSERS) and two-dimensional correlation spectroscopy (2DCOS) analysis was demonstrated for the in situ identification of xanthine analogues in their ternary mixture. The DSERS method with an optimized initial pH value allows monitoring the distinct pH-dependent spectral evolution among analogues in real time, enhancing the spectral selectivity. Moreover, complex variations in pH-dependent spectral sets were further interpreted by 2DCOS. Consequently, xanthine analogues in their ternary mixture were distinguished from each other on the basis of characteristic peaks in 2DCOS maps. This combined strategy between DSERS and 2DCOS offers a prospect in studies of in situ analysis of structural analogues involving mixture specimens. Graphical abstract Schematic diagram illustrating the collection of pH-dependent SERS spectra by dynamic-SERS method, the procedure of two-dimensional correlation analysis and the identification basing on asynchronous maps.