isosbestic point


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isosbestic point

[‚ī·səs‚bes·tik ′point]
(physical chemistry)
During a chemical reaction, a point in the absorption spectrum (that is, a wavelength) where at least two chemical species (for example, reactant and product) have identical molar absorption coefficients, which remain constant as the reaction proceeds. A stable isosbestic point is evidence that a reaction is proceeding without forming an intermediate or multiple products.
References in periodicals archive ?
When an isosbestic plot is constructed by the superposition of the absorption spectra of two species (whether by using molar absorptivity for the representation, or by using absorbance and keeping the same molar concentration for both species), the isosbestic point corresponds to a wavelength at which these spectra cross each other.
Fura-2 fluorescence was alternately excited at the isosbestic point (357 nm) and at the calcium-sensitive wavelength (.
Overlapping the absorbance spectra for mixtures of ITX and MA having differing irradiation times between 0 and 60 min showed that a single isosbestic point was produced at approximately 350 nm (Fig.
While in the presence of increasing concentration of CTAB in a fixed concentration of 5-FU, the signal at 206 nm showed increase in absorbance (hyperchromic effect) accompanied with red shift (bathochromic effect), generation of another signal at 296 nm and an isosbestic point.
The isosbestic point 158 may, presumably, be due to equal increase of DNA fragments by the probable DNA damage with the increasing in concentration of the compound- DNA complex.
6), we scanned the excitation spectra of the coproporphyrin calibrator and the real fecal samples from 340 to 450 nm, while monitoring the emission at 668 nm, the emission isosbestic point for coproporphyrin and protoporphyrin.