Light scattering extinction coefficient, determination

Crawley et. al. [57] applied the above equations to determine particle size distributions from turbidity measurements. The problems arise in finding a particle size distribution from the measured extinction coefficient due to the ill-defined inversion problem. Scholtz et.al. [58] focused on the problem of analyzing spectra of colloidal solutions, for which the size distribution was known from other methods like electron microscopy and light scattering they termed this transmission spectroscopy. ... 

The solubilization of eumelanins has been attempted under a variety of conditions. Table IV summarizes the results obtained with some native melanins (300). A melanin is considered completely solubilized if the solution does not scatter light. So far only two approaches have been successful, one of which is based on treating the pigment with Solulene 100 (0.1 M solution of dimethyl- -dodecyl-n-undecyl ammonium hydroxide in toluene incubation for 2.5 hr at 75 C). Such solutions were used in the characterization and quantitative determination of melanins (124,301). The extinction coefficient (absorption at 400 nm) for hair melanin was of the order of 3000 Af" cm per indole unit, while that of melanoma melanin was only about 70% that of synthetic dopa melanin (124). The mechanism of the Solulene solubilization process is unknown, and degradation of the pigment cannot be excluded. Interestingly, full neutralization of the melanin solution in Solulene with acetic acid did not precipitate the pigment (302). 

The basic theory for the study of the scattering of light by aerosols was presented by Mie (1908). This theory generally assumes an ensemble of identical spherical particles and requires considerable computing resources for its solution. Modifications to allow for cylindrical and ellipsoidal particles have also been developed. In practice, simplified formulas are often used (see, e.g., Van de Hulst, 1957). The total extinction coefficient at a particular wavelength can be determined by integration over all particle radii r... 

The extinction coefficient of bovine GDH has been subject to some debate. A value of = 0.97 cm mg at 279 nm was obtained by Olson and Anfinsen 11). More recently, it was noted that light scattering from a solution of about 0.5 mg/ml contributes about 20% to extinction at 279 nm, and a corrected value of E l ° = 0.83 cm mg, equivalent to a molar extinction coefficient of 46.5 X 10 cm mole , was obtained this gave closer agreement to the extinction coefficient calculated from the tyrosine and tryptophan content found by sequence determination 163). Other workers found a corrected value = 0.89 cm mg ... 

Notes pH 8.0 0.1, saturated with air or N2O. Bandpass 3-6 nm baseline recorded 2-3 ms after flash data prior to 80-100 ys deleted due to scattered light distortion, (a) a = mean exponential rate determined by KIXKIN for individual runs (b) fi =Mean second order rated for Rll divided by moler extinction coefficient for Br2 radical as determined by MIXKIN for individual runs (c) Multiplied by extinction coefficient for Br2 as a function of wavelength (10). 

An is the contribution to the refractive index due to the solute whose concentration is C (mol/L), c is the speed of light, and e(vO is the molar extinction coefficient. An is the difference between the refractive indexes of the solution and the solvent. An is essentially the isotropic contribution to the refractive index by the solute whose absorption spectrum determines e(vO. It should not be confused with birefringence, which uses the same symbol (see under Birefringence). A common application of the Kramers-Rronig relation appears in light scattering, especially when one is interested in the effects of scattering on absorbance measurements. 

Since the UV response as a measure of purity and quantity determination is questionable due to the different extinction coefficients of individual components of a crude preparation, alternative detection systems were advocated, such as the evaporative light scattering detector (ELSD) and the chemiluminescent nitrogen detector (CLND). " In addition, NMR techniques were adopted that allowed structural confirmation, purity characterization, compound solubility, solution stability, and biological testing from a single DMSO stock solution. The quality control process for descriptions of chemical library members was discussed by Yan in 2004. ... 

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