Combining excitation-emission matrix fluorescence spectroscopy, parallel factor analysis, cyclodextrin-modified micellar electrokinetic chromatography and partial least squares class-modelling for green tea characterization

Abstract

In this study, an alternative analytical approach for analyzing and characterizing green tea (GT) samples is proposed, based on the combination of excitation-emission matrix (EEM) fluorescence spectroscopy and multivariate chemometric techniques. The three-dimensional spectra of 63 GT samples were recorded using a Perkin-Elmer LS55 luminescence spectrometer; emission spectra were recorded between 295 and 800 nm at excitation wavelength ranging from 200 to 290 nm, with excitation and emission slits both set at 10 nm. The excitation and emission profiles of two factors were obtained using Parallel Factor Analysis (PARAFAC) as a 3-way decomposition method. In this way, for the first time, the spectra of two main fluorophores in green teas have been found. Moreover, a cyclodextrin-modified micellar electrokinetic chromatography method was employed to quantify the most represented catechins and methylxanthines in a subset of 24 GT samples in order to obtain complementary information on the geographical origin of tea. The discrimination ability between the two types of tea has been shown by a Partial Least Squares Class-Modelling performed on the electrokinetic chromatography data, being the sensitivity and specificity of the class model built for the Japanese GT samples 98.70% and 98.68%, respectively. This comprehensive work demonstrates the capability of the combination of EEM fluorescence spectroscopy and PARAFAC model for characterizing, differentiating and analyzing GT samples.

Light and Autofluorescence, Multitasking Features in Living Organisms

“…Such compounds are particularly abundant in green and black tea and may have beneficial effects on human health or influence on drug pharmacokinetics in human plasma [114,115]. For these reasons spectral fluorescence analysis has been recently successfully proposed as a valuable support to assess quality and origin of tea [116,117]. cence has been ascribed to hydroxycinnamoyl derivatives, proposed to favor the visual attraction for pollination insects as well as to protect from potential UV damage [112].…”

Application of Molecular spectroscopy and chemometrics for authentication and quality control of tea (Camellia sinensis L.): a review

“…PCA, PARAFAC, PLS-DA the combination of fluorescence spectra and PLS-DA provide the discrimination of green tea samples with accuracy levels of sensitivity and specificity of 98.70% and 98.68%, respectively. (Casale et al, 2018).…”

“…Using the optimum condition (pre-processing and selection of appropriate variable), the combination of fluorescence spectra and PLS-DA provide the discrimination of green tea samples with accuracy levels of sensitivity and specificity of 98.70% and 98.68%, respectively. This developed method demonstrates the capability of the combination of fluorescence spectroscopy and PARAFAC model for characterizing, discriminating and classification of green tea samples according to its origin (Casale et al, 2018).…”

Analytical Chemistry and Chemometrics Group, Department of Pharmacy, University of Genova: An update

“…In 2018, Eleonora Mustorgi became the new PhD student, after graduating in Pharmacy with an MSc thesis carried out in the Group Lab. 2 But the heart of the Team is still the same, with some deserved career advancements: Professor Riccardo Leardi is now the “Dean” of the Group, continuing his work in chemometrics with unchanged passion; Professor Monica Casale is now beginning her new responsibility as an associate professor while holding the position of President for the Italian Society of NIR Spectroscopy (SISNIR) 3 ; Professor Paolo Oliveri has been confirmed as an assistant professor in the research group and was recently elected Coordinator for the Divisional Group of Chemometrics within the Italian Chemical Society. 4 Last but not least, Dr Chiara Casolino is tirelessly supporting the Team, playing a crucial role in the organization of the Chemometric School of Genova, a regular meeting point for many researchers approaching chemometrics.…”