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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
He chose wavelengths of 630 nm (red) and 900 nm (infrared) for the oximeter, the latter being different to the 805 nm chosen by previous workers which coincided with the point of equal absorption by haemoglobin and oxyhaemoglobin (isobestic point).
Modern pulse oximeters may use two or more wavelengths, not necessarily including an isobestic point (Fig 2).
The absorption peaks correspond well to reference spectra downloaded from the database of the National Institute of Standards and Technology (NIST) [41, 42], although the isobestic point is shifted from 7.60 to 7.65 [micro]m with the QCL system.