Functioning of a Fluorescein pH-Probe in Aqueous Media: Impact of Temperature and Viscosity

In this work, we considered the influence of viscogenic agents (glycerol, sucrose) as well as the temperature on the fluorescent characteristics of fluorescein at pH 6.5 in order to describe the acid-base status of local environment in terms of a spectrally detectable dianion-anion equilibrium. The...

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Bibliographic Details
Published in:Micromachines (Basel) 2023-07, Vol.14 (7), p.1442
Main Authors: Surzhikova, Darya P, Sukovatyi, Lev A, Nemtseva, Elena V, Esimbekova, Elena N, Slyusareva, Evgenia A
Format: Article
Language:English
Subjects:
Anions
Aqueous solutions
chemosensor
Data processing
Dyes
Enthalpy
Equilibrium
Fluorescein
Fluorescence
Glycerol
Hydrogen bonds
Hydrogen-ion concentration
Measurement
Molecular dynamics
Optical properties
protolytic equilibrium
ratiometric signal
Software
Spectrum analysis
steady-state fluorescence
Sucrose
Temperature
Testing
Viscosity
Water chemistry
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Summary:In this work, we considered the influence of viscogenic agents (glycerol, sucrose) as well as the temperature on the fluorescent characteristics of fluorescein at pH 6.5 in order to describe the acid-base status of local environment in terms of a spectrally detectable dianion-anion equilibrium. The protolytic equilibrium of fluorescein was found to depend on the solvent viscosity in a complex way. Whereas in the presence of sucrose the ratiometric signal of fluorescein (I /I ) remains rather unchanged, the addition of glycerol (up to 40% / ) results in the increase of the signal (up to 19%), that can be attributed to the different mechanisms of cosolvents effects on dye molecules in the ground state. Molecular dynamics of the dye in the presence of glycerol and sucrose revealed that the cosolvents preferentially interact with fluorescein monoanion and dianion, displacing water molecules from the local environment which in turn reduces the average number of the hydrogen bonds between xanthene ring of the dye and water molecules. The ratiometric signal demonstrates linear growth with the temperature in the range of 10-80 °C regardless of the presence of viscogenic agents. A linear correlation between the temperature sensitivity of the ratiometric signal and the change in the molar enthalpy of the proton dissociation reaction in buffer and viscous media was determined.
ISSN:2072-666X
2072-666X
DOI:10.3390/mi14071442