Search results
Results from the WOW.Com Content Network
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]
Ellman's original 1959 publication estimated the molar extinction at 13,600 M −1 cm −1, and this value can be found in some modern applications of the method despite improved determinations. [6] Commercial DTNB may not be completely pure, so may require recrystallization to obtain completely accurate and reproducible results.
A. R. Forouhi and I. Bloomer deduced dispersion equations for the refractive index, n, and extinction coefficient, k, which were published in 1986 [1] and 1988. [2] The 1986 publication relates to amorphous materials, while the 1988 publication relates to crystalline.
Pages for logged out editors learn more. Contributions; Talk; Molar extinction coefficients
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.
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
Thus, for a fixed path length, UV-Vis spectroscopy can be used to determine the concentration of the absorber in a solution. It is necessary to know how quickly the absorbance changes with concentration. This can be taken from references (tables of molar extinction coefficients), or more accurately, determined from a calibration curve.