Effects of chromophoric dissolved organic matter on the optical properties of different fluorescent probes

Abstract

The new detection technology represented by fluorescent probe is an effective supplement to the traditional instrument analysis of environmental pollutants. However, background interference is an inevitable obstacle in the fluorescent analysis of complex samples. Dissolved organic matter (DOM) in water is widespread and significantly affects the performance of fluorescent probes in pollutants detection. In this work, the impact of DOM on the performance of fluorescent probes were investigated under different conditions. Firstly, three-dimensional fluorescence spectroscopy of local lake was performed to identify the composition of organic matter in water. The types of chromophoric DOM in local lake mainly include humic acids and tryptophan, and its concentrations varied over time and across different regions. Then, three fluorescent probes with different fluorescence emission were selected to investigate the interaction between DOM (humic acids, tryptophan, and fulvic acid as the interfering substances) and fluorescent groups. The experimental results demonstrated that humic acid significantly reduced the signal intensity of fluorescent probes through mechanisms such as inner filter effects and fluorescence resonance energy transfer. In contrast, tryptophan and fulvic acid had relatively minor impacts. More importantly, the altered pH and ions of the environmental water did not significantly alter the interference of DOM on fluorescent probe. To further verify the influence of chromophoric DOM on fluorescent probes in real water, the water treatment under UV irradiation with H₂O₂ was used for the preparation of simulated water samples. The influence of DOM on fluorescent probes in real water samples was also similar to that in buffer. These results suggested that the chromophoric DOM can effectively affect the spectral properties of different fluorescent probes, and greatly interfere with the sensitivity and accuracy of fluorescence detection. This work help to understand the interference mechanisms of DOM in water, and are significant for improving the accuracy of fluorescent probes in water quality monitoring applications.