*2.1. Determination of Zearalenone by Autofluorescence*

Detection capability of ZON by its own induced fluorescence was assessed in direct fluorescence (autofluorescence) measurements in water. A fluorescence intensity spectral map and a calibration curve are presented on Figure 1. Fluorescence is generated by the optical excitation of electrons, which emit fluorescent light when they return to their ground state from their excited state. As a loss of vibrational energy inevitably occurs during this process, the emission spectrum is shifted to longer wavelengths than the excitation wavelength (Stokes shift). Figure 1 depicts the relevant wavelength pairs of excitation and emission of fluorescence spectra, as well as the dependence of intensity of the emitted light (fluorescence) on the concentration of ZON. Excitation mapping was carried out by scanning emission intensities as a function of excitation intensities between 250 and 830 nm wavelengths depicting emission intensity in a color scale from blue to red (Figure 1a). On the basis of the fluorescence spectral map, the optimized peak for ZON measurement by autofluorescence was obtained with excitation at 280 nm wavelength and emission detection at 520 nm wavelengths. The dependence of the emitted light at these parameters on the

concentration of ZON in the aqueous sample was also tested and was found to follow a sigmoidal (logistic) regression (Figure 1b). Based on the sigmoid curve for autofluorescence, an LOD value of 11.5 µg/mL was determined. rameters on the concentration of ZON in the aqueous sample was also tested and was found to follow a sigmoidal (logistic) regression (Figure 1b). Based on the sigmoid curve for autofluorescence, an LOD value of 11.5 µg/mL was determined.

830 nm wavelengths depicting emission intensity in a color scale from blue to red (Figure 1a). On the basis of the fluorescence spectral map, the optimized peak for ZON measurement by autofluorescence was obtained with excitation at 280 nm wavelength and emission detection at 520 nm wavelengths. The dependence of the emitted light at these pa-

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**Figure 1.** Results of zearalenone (ZON) quantification by autofluorescence. (**a**) A fluorescence spectral map of ZON in phosphate buffer saline and the optimized peak (in the range of a red patch, the middle point of cross-hair indicating optimal detection conditions) with 280 and 520 nm wavelengths for excitation (ordinate) and emission (abscissa), respectively. (**b**) A calibration curve obtained in a concentration range between 175 and 1,000,000 ng/mL of ZON and the chemical structure of ZON (insert). **Figure 1.** Results of zearalenone (ZON) quantification by autofluorescence. (**a**) A fluorescence spectral map of ZON in phosphate buffer saline and the optimized peak (in the range of a red patch, the middle point of cross-hair indicating optimal detection conditions) with 280 and 520 nm wavelengths for excitation (ordinate) and emission (abscissa), respectively. (**b**) A calibration curve obtained in a concentration range between 175 and 1,000,000 ng/mL of ZON and the chemical structure of ZON (insert).
