Application of Double Two-Dimensional Correlation Spectroscopy in Detection of Adulterated Black Tea

Compared with the conventional synchronous 2D correlation spectroscopy, double 2D correlation spectroscopy, which improves the spectral resolution, can effectively capture the feature information of complex system. In present study, conventional 2D and double 2D correlation spectroscopy combined with fluorescence spectroscopy, UV-Vis absorption spectroscopy were applied to extract and identify the characteristic peak of carmine in tea. The fluorescence spectra and UV-Vis absorption spectra of black tea samples adulterated with different concentration of carmine were collected. The conventional 2D and double 2D fluorescence, UV -Vis correlation spectra were constructed under the perturbation of carmine concentration in black tea. For double 2D fluorescence correlation spectrum, there are two auto-peaks at 423 and 472 nm, whereas there is only one auto-peak around 429 nm in conventional synchronous spectrum. For double 2D UV -Vis correlation spectrum, the auto-peaks are observed at 235, 278, and 388 nm, which are obscured in the 2D correlation spectrum. The double hetero-2D fluorescence-UV-Vis correlation spectrum further confirmed the origin of the peaks. The results show that double 2D correlation spectra can present much more detailed characteristic information compared to the conventional 2D correlation spectra.