Quantitative spectrophotometry using integrating cavities

The Multicenter Aerobic Iron Respiratory Chain of Acidithiobacillus ferrooxidans Functions as an Ensemble with a Single Macroscopic Rate Constant

“…Previous studies demonstrated that raw absorbance spectra obtained with integrating cavity absorption meters appeared distorted compared with the corresponding spectra of the same materials obtained using a conventional linear spectrophotometer (27)(28)(29)(30). Unlike single path length spectrophotometers where the Beer-Lambert law governs nonlinearity in the measured light intensity as a function of analyte concentration, the measuring light in the CLARiTY makes multiple random passes with different path lengths that exacerbate the apparent nonlinearity with analyte concentrations.…”

“…The premise was that accurate UV-visible spectroscopy of electron transfer reactions among colored proteins could be conducted in highly turbid suspensions if the live bacteria were irradiated in an isotropic homogeneous field of incident measuring light. Under those conditions, the absorbed radiant power should be independent of scattering effects (27)(28)(29)(30). Equilibrium and kinetic studies were conducted on the Fe(II)-dependent reduction and O 2 -dependent oxidation of cytochromes in intact Leptospirillum ferrooxidans at pH 1.7 (26).…”

Innovative spectroscopy of liquids: a fiber optic supercontinuum source and an integrating sphere for scattering-free absorption measurements

“…Diffuse-light absorption spectroscopy, that is, spectroscopy carried out by means of an integrating cavity, is a valid alternative for overcoming scattering-dependence aspects [4][5][6][7]. Unfortunately, because it requires high-intensity sources, diffuse-light absorption spectroscopy provides low efficiency when carried out by means of optical fibers for illumination and detection.…”

“…summarizes the results of spectral data processing, reporting the central wavelength, the optimal spectral window width, together with R 2 and the SECV.Figures 4,5,and 6 show PLS regression plots correlating the true and predicted values of the selected lubricant oil quality parameters: phosphorous, TAN and water, respectively. The correlation is excellent for phosphorous, it is very good for TAN, and it is more than acceptable for water.…”

Screening hypochromism (sieve effect) in red blood cells: a quantitative analysis

“…Reliable methods for finding the true absorbance, either by separating the contribution made by scattering [1] or by circumventing it altogether by placing the sample inside an integrating cavity [2], have been available for some time. A 2004 paper [3], written by the present author and his associates, suggested a practicable procedure for a quantitative analysis of the scattering spectrum by dividing it into two parts, one caused by selective scattering and the other by non-selective scattering; the approach, which relied on the assumption that absorption and selective scattering from a single pool of pigments satisfy the Kramers-Kronig relations and on a milder assumption concerning the wavelength dependence of non-selective scattering, was shown to account for the scattering an absorption spectra of a wide variety of suspensions, including those of red blood cells.…”