ИСТИНА

The PARAFAC decomposition is widely used in the analysis of fluorescence data, owing to its direct correspondence to the underlying physical processes. Unfortunately, excitation-emission matrices (EEMs) typically contain scattering signals in addition to fluorescence, making it a requirement to handle the scattering signal either before or as part of the PARAFAC decomposition. Interpolation of the areas affected by the scattering signal [1] makes it possible to perform PARAFAC decomposition of EEMs while avoiding the local minima, but it may introduce artefacts in the shape of the resulting loadings, or even hide a component if it happens to fully overlap with a second order scattering band. In this work, an approach based similar to multivariate curve resolution (MCR) with trilinear constraints [2] is applied to the task of modelling both the fluorescence and the scattering signal. On every iteration of the algorithm, PARAFAC and MCR fit each other’s residuals, converging towards fluorescence being described by the PARAFAC model and the scattering signal in the MCR model. Typical limitations of this approach are nonlinearities arising from the detector being close to saturation when measuring scattering signal. Constraints fixing the values of the MCR components outside the scattering bands to zeros, use of multiple MCR components, and strategic positioning of missing data may be required to deal with these limitations. The approach has been tested on various EEM datasets, including fully synthetic, amino acid mixtures, sugar process data, and seawater DOM. Example results of the suggested approach – emission and excitation PARAFAC loadings and the scattering signal loadings – are presented in the Figure. We can also conclude that the suggested approach provides better level of precision in reconstruction of original components. The reported study was funded by RFBR, project number 20-33-90280. [1] Bahram M.; Bro R.; Stedmon C.; Afkhami A.; Handling of Rayleigh and Raman scatter for PARAFAC modeling of fluorescence data using interpolation, Journal of Chemometrics. 2006, 20, 99–105. [2] Tauler R.; Marqués I.; Casassas E.; Multivariate curve resolution applied to three-way trilinear data: Study of a spectrofluorimetric acid–base titration of salicylic acid at three excitation wavelengths, Journal of Chemometrics, 1998, 12, 55–75.