Methanol, as one of the organic solvents, is commonly used for the detection of organic pollutants by ultraviolet (UV)fluorescence spectroscopy. However, the effect of methanol as an intermediate solvent on the fluorescence spectral intensity of benzene has not been reported in the literature. It has been experimentally shown that methanol molecules affect the spectral detection results of benzene, so it is of great significance to study the fluorescence spectral properties of organic solvents with different methanol volume fractions. In this paper, the fluorescence spectra of benzene and toluene are analyzed based on the principle of fluorescence detection by measuring the methanol-water solutions of benzene and toluene with different methanol volume fractions. The fluorescence spectra of the two substances are analyzed in terms of the solvation effect, the coplanar arrangement (π-π interaction) and vibrational relaxation (non-radiative jump) of the molecules, and the fluorescence burst effect at high polarity ratios, and the fluorescence spectra of benzene and toluene under different methanol volume fractions are investigated. The effects of methanol volume fraction on the fluorescence spectra of benzene and toluene solutions are investigated at the level of coplanar arrangement (π-π interaction) and vibrational relaxation (non-radiative jump) of molecules and fluorescence burst effect at high polarity ratios. The experiments verify that the fluorescence intensities of benzene and toluene are affected by different methanol volume fractions, which provides a theoretical basis and practical reference for the fluorescence spectroscopic detection of benzene with methanol as the intermediate solvent, and provides a new perspective for the fluorescence detection method.

The assay method used in this experiment is the fluorescence method, which is an analytical method commonly used for detecting and measuring fluorescence signals in samples. After the fluorescent substance in the liquid is excited by the incident light, the fluorescence intensity can be observed in all directions of the solution. In this paper, the fluorescence spectra of benzene and toluene are analyzed based on the principle of fluorescence detection by measuring the methanol-water solutions of benzene and toluene with different methanol volume fractions, and the effects of methanol on the fluorescence spectral intensities of the benzene and toluene solutions are investigated at the level of intermolecular coplanar arrangement and vibrational relaxation. The fluorescence spectra of the benzene and toluene solutions with different methanol volume fractions are tested for the influence of fluorescence spectroscopy detection and the results are analyzed.

In this paper, the fluorescence spectra of benzene and toluene are analyzed based on the principle of fluorescence detection by measuring the methanol-water solutions of benzene and toluene with different methanol volume fractions. The fluorescence spectra of the two substances are analyzed from the dimensions of the solvation effect, the intermolecular coplanar arrangement (π-π interaction) and the vibrational relaxation (non-radiative jump), and the effect of the fluorescence burst at a high polar ratio, to study the effect of solvents on fluorescence intensities of benzene and toluene with different methanol volume fractions. The fluorescence spectrum detection experiments are carried out. The analytical results show that the fluorescence spectral intensities of benzene and toluene have an overall increasing trend with increasing the methanol volume fraction when the mass concentration of benzene is 100, 200, and 300 mg/L, the mass concentration of toluene is 1, 20, and 40 mg/L, and the methanol volume fraction is from 0% to 70% with a good linearity. At the higher methanol volume fractions (>70%), the fluorescence intensities of benzene and toluene show a decreasing trend with increasing the methanol volume fraction. In the range of 0%?90%, the change of the fluorescence intensities of benzene and toluene shows an overall nonlinear relationship. The experiments verify that different solvents with different methanol volume fractions have different effects on the fluorescence intensities of benzene and toluene, which provides a theoretical basis and practical application reference for the fluorescence spectroscopic detection of benzene with methanol as the intermediate solvent, and provides a new perspective for the fluorescence detection method.

In this paper, the effect of methanol volume fraction on the fluorescence spectral intensities of benzene and toluene solutions is investigated, and the influence mechanisms are comprehensively analyzed. By the fluorescence spectroscopy analysis, the effect of methanol volume fraction on the fluorescence spectra of benzene and toluene is mainly the change of fluorescence intensity. The analysis results show that the fluorescence intensities of benzene and toluene have an overall increasing trend with the increase of methanol volume fraction when the methanol volume fraction is 0%?70% with a good linearity, while the fluorescence intensities of benzene and toluene show a decreasing trend with the increase of methanol volume fraction at higher methanol volume fractions (>70%). In this paper, the effect of different methanol volume fractions (0%?90%) on the fluorescence intensity of benzene is investigated in terms of solvation effect, intermolecular hydrogen bonding, and molecular aggregation, and it is found that the hydroxyl group of methanol can interact with the electron clouds of benzene and toluene through hydrogen bonding to form a stable solvated structure. This process not only reduces the benzene-benzene and toluene-toluene-stacking interactions and improves the molecular dispersion, but also restricts the vibrational and rotational degrees of freedom of the molecules, which suppresses the vibrational relaxation and leads to the enhancement of the fluorescence intensity. However, at higher methanol volume fractions (>70%), the solvation effect and hydrogen bonding further affect the electron cloud distribution of benzene molecules due to the enhanced solvent polarity, while the aggregation of benzene and toluene molecules occurs, which leads to the enhancement of the fluorescence burst effect and a decrease in the fluorescence intensity. This phenomenon is different from the traditional linear effect, revealing a synergistic mechanism of solvation, non-radiative jump, and fluorescence burst effect. The analytical study of these influencing trends and laws provides reference for the future fluorescence spectroscopic detection and analysis of benzene using methanol as intermediate solvent, especially in the fields of organic pollutant detection, petrochemical and food detection, which has important practical application value.