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The SI unit of molar absorption coefficient is the square metre per mole (m 2 /mol), but in practice, quantities are usually expressed in terms of M −1 ⋅cm −1 or L⋅mol −1 ⋅cm −1 (the latter two units are both equal to 0.1 m 2 /mol).
It also has a smaller local excitation maximum around 343 nm. The molar extinction coefficient is about 13,000 cm −1 M −1 and its overall effective fluorescence is about 1% that of fluorescein. It is only mildly sensitive to halide ion collision quenching. NBD-TMA was designed as a probe for monitoring renal transport of organic cations. [1]
This quantity is called the extinction coefficient and denoted κ. In accordance with the ambiguity noted above , some authors use the complex conjugate definition, where the (still positive) extinction coefficient is minus the imaginary part of n _ {\displaystyle {\underline {n}}} .
Then the following formula is used to calculate the first extinction coefficient: W*5500 + Y*1490 + cystines*125. This calculation assumes that all cysteines pair into cystines. The second version assumes that all cysteines are reduced and there are no cystines, thus it is calculated as W*5500 + Y*1490.
The molar extinction coefficient of Hb has its highest absorption peak at 420 nm and a second peak at 580 nm. Its spectrum then gradually decreases as light wavelength increases. On the other hand, H b O 2 {\displaystyle HbO2} shows its highest absorption peak at 410 nm, and two secondary peaks at 550 nm and 600 nm.
This reaction is rapid and stoichiometric, with the addition of one mole of thiol releasing one mole of TNB. The TNB 2− is quantified in a spectrophotometer by measuring the absorbance of visible light at 412 nm, using an extinction coefficient of 14,150 M −1 cm −1 for dilute buffer solutions, [4] [5] and a coefficient of 13,700 M −1 cm −1 for high salt concentrations, such as 6 M ...
Extinction coefficient refers to several different measures of the absorption of light in a medium: Attenuation coefficient , sometimes called "extinction coefficient" in meteorology or climatology Mass extinction coefficient , how strongly a substance absorbs light at a given wavelength, per mass density
Variable pathlength absorption spectroscopy uses a determined slope to calculate concentration. As stated above this is a product of the molar absorptivity and the concentration. Since the actual absorbance value is taken at many data points at equal intervals, background subtraction is generally unnecessary.