On the spectral separation of dye mixtures

The fluorescent tracers technique for determining hydraulic and transport parameters in the field and in the laboratory is well established. Common practices include the use of multiple dyes in branches of convergent streams, or the use of multiple dyes to control the quality of the results. However, the quantification of dye mixtures cannot be done correctly by calibration curves constructed from fluorescence intensity peaks. This problem arises because the characteristic wavelengths of the tracers are close, and their fluorescence spectra are wide, which leads to mutual interference in samples containing mixtures of dyes. To assess a spectral separation method, a set of standard solutions containing single tracer and binary mixtures of dyes was prepared and measured using a spectrofluorometer. The fluorescence spectra were processed by software routines written for background subtraction and spectral separation. Pearson Type VII curves fitted well to the fluorescence spectra of the selected dyes and were used to calculate the contribution of each tracer in the mixture by an additive model. The difference between the calculated and the nominal values was smaller after spectral separation and dependent on the concentration ratio of the tracers. Mixtures that had one of the dyes in low concentration could not be detected by the traditional peak method but could be detected and quantified after spectral separation. The support of software routines can lead to higher productivity and improved data quality, and a spectral separation method should be a standard procedure for measuring dye mixtures.

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Opracowanie rekordu ze środków MEiN, umowa nr SONP/SP/546092/2022 w ramach programu "Społeczna odpowiedzialność nauki" - moduł: Popularyzacja nauki i promocja sportu (2022-2023).