A new generalized algorithm for conversion of synchronous fluorescence matrices in excitation-emission matrices for applications in second order analysis

Synchronous fluorescence is a useful spectroscopic technique for measuring fluorescence at a fixed offset from the excitation wavelength. Synchronous fluorescence matrices (SFMs) created by changing both the excitation and the offset do not exhibit any bilinear characteristics, unlike excitation-emission matrices (EEMs), impeding their use with multilinear techniques. This work proposes a new generalized algorithm for converting any SFMs into EEMs in a quick and efficient manner without distortions while minimizing empty spaces, joining the instrumental advantages of SFMs with the data processing advantages of EEMs. The proposed algorithm obtained consistent EEMs from SFMs, whose data arrangement will be determined solely by the ratio of the offset and excitation steps. SFM datasets of PAHs at different step ratios were measured and their PARAFAC models were used to assess its usability and compare it with a previously proposed algorithm. CORCONDIA values confirmed model trilinearity (between 74 and 99 %) and instrumental profiles were recovered; however, results varied with different step ratios. In matrices where the excitation step was a multiple of the offset step, the conversion was equivalent to a shearing transformation, yielding better deconvoluted profiles when compared with others, which could produce grid-like patterns complicating visual identification of some components. While this points to an optimal application of it being made with those specific step ratios, the algorithm also provides legacy support for datasets measured differently. The algorithm development allowed the use of any SFM datasets with bilinear/trilinear algorithms able to handle empty spaces, without the limitations of previously suggested conversion algorithms.