Extinction coefficient for

In view of the chromophoric character of the elemental iodine itself, many colorimetric methods have been proposed for the deterrnination of inorganic iodine (88—92). These methods use the visible portion of the spectmm in reading iodine concentrations. In the visible range the extinction coefficient for iodine is not high enough to be used for minute quantities of iodine in water and other solvents (93). Higher sensitivities have been reported for elemental iodine in potassium iodide solutions in the ultraviolet (93,94). 

The Rayleigh scattering extinction coefficient for particle-free air is 0.012 km for "green" light (y = 0.05 /rm) at sea level (4). This permits a visual range of —320 km. The particle-free, or Rayleigh scattering, case represents the best visibility possible with the current atmosphere on earth. 

Ozin et al. 107,108) performed matrix, optical experiments that resulted in the identification of the dimers of these first-row, transition metals. For Sc and Ti (4s 3d and 4s 3d, respectively), a facile dimerization process was observed in argon. It was found that, for Sc, the atomic absorptions were blue-shifted 500-1000 cm with respect to gas-phase data, whereas the extinction coefficients for both Sc and Scj were of the same order of magnitude, a feature also deduced for Ti and Ti2. The optical transitions and tentative assignments (based on EHMO calculations) are summarized in Table I. 

Cryophotochemical techniques have been developed that (i) allow a controlled synthetic approach to mini-metal clusters 112), Hi) have the potential for "tailor-making small, bimetallic clusters (mini-alloy surfaces) 114,116), Hi) permit the determination of relative extinction-coefficients for naked-metal clusters 149), and iv) allow naked-cluster, cryophotochemical experiments to be conducted in the range of just a few atoms or so 112,150,151). 

The relative extinction-coefficients for Agi,2,s determined by pho-toaggregation procedures were found not to be strongly matrix-dependent (see Table VIII). Moreover, the results for Agj were in good agreement with those obtained by quantitative, metal-atom deposition-techniques. 

In c.d., the characteristic of the molecule that is seen is the difference in extinction coefficient for the two types of circularly polarized light. Each type of light obeys Beer s Law, so that... 

Detailed Investigation of this B L conversion suggests that about 2Bi + 2L occur for each L - CO adsorbed. The stoichiometric relationship Induced by L - CO adsorption causing 2 i 2L Is shown In Figure 7, where Isotoplcally labeled CO has been employed In separate experiments as or as L. After a small correction Is made for the experimentally determined difference In extinction coefficient for 3co(ads) compared to 12co(ads), It may be seen that the stoichiometry 2B + L -> 3L Is closely verified. 

The extinction coefficient for non-ahsorbing particles may be theoretically evaluated from the ligjit scattering theory developed by Mie (lU, 1 ). It is calculated from the relationship... 

Table I compares the measured values of extinction coefficients with the values calculated from theory at wavelengths of 25U, 280 and 350 nm. The lower values of extinction coefficients for the larger particles measured, using the online detector compared to the Beckman instrument, are due to the optical effects discussed above. The disagreement between the extinction coefficients calculated from Mie theory for non-absorbing spheres and the measured values from the Beckman instrument is very significant, particularly at 2 k and 280 nm.

Extinction coefficients for the various nitrates and nitrites are collected in Table I. Our experimentally determined IR extinction coefficients for other species are collected in Table II. It must be emphasized that the methods discussed above do not quantify all possible oxidation products. An obvious omission is the absence of a reliable method for dialkyl peroxides. An HI based method has been suggested in the literature, but proves to be extremely imprecise on film samples in our laboratories because of large reagent blanks (27). 

If we know the extinction coefficients for the two isomers at the wavelength of photolysis (3130), it should be possible to calculate the pss for the direct photolysis from... 

The use of electrochemical transmittance spectroscopy in both the UV-visible and IR regions of the spectrum is elegantly shown by the work of Ranjith et al. (1990) who employed an OTTLE cell to study the reduction of benzoquinone, BQ. The authors were the first to report the UV-visible spectrum of BQ2- and to demonstrate the quantitative aspects of the technique by reporting extinction coefficients for the major bands of BQT and BQ2- in both the UV-visible and IR. 

By employing an extinction coefficient for the anion radical obtained from the pulse radiolysis experiments, the concentration of the radical could be calculated, and plotted against /c. The straight line plot so obtained was taken as strong evidence for the ECE mechanism, i.e. the solution phase attack of C02 on C02, thus fully resolving the controversy over the identity and state of the intermediate. From the slope of the plot the authors obtained the rate constant k2 as 7.5 x I03dm3mol 1 s 1. 

Measure the absorbance of the biotinylated protein solution at 354 nm. Use the molar extinction coefficient for the chromogenic group (e = 29,000 M-1cm-1) to determine the concentration of biotin present. To determine the molar ratio of biotin-to-protein, divide the molar concentration of biotin by the molar concentration of protein present (which may be determined by using the Coomassie assay or the BCA assay methods). 

The formed radicals are excited at A = 313nm and an excess of energy is equal to 320 kJ mol-1, at X 254 nm, it is equal to 230kJ mol-1. This is the reason for the gas-phase photolysis leading to intensive decomposition of the formed alkoxyl radicals. The values of A max and extinction coefficients for several peroxides are presented [205] ... 

Emeis, C.A. Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on sohd acid catalysts. J. Catal. 1993,141, 347-354. 

The dication 212+ exhibited a reduction wave upon CV at a less negative potential than that of 3b+. This wave corresponds to a one-step, two-electron reduction of 212+. In the electronic spectra, dication 212+ also showed strong absorption in the visible region. The extinction coefficients for the dication was almost twice as large as those of monocations. The deep-blue color of the... 

Another proton transfer studied by the E-jump technique in acetonitrile (42) is that between p-nitrophenol (AH) and tri-ethylamine (B). The extinction coefficients for each of the species in the following equilibrium have been measured by Kree-voy and Liang (3) ... 

Sensitivity. The measured fluorescence parameter of an indicator should be sensitive to changes of analyte in the desired concentration range, as summarized in Table 10.1 for a number of analytes. The indicator should have high extinction coefficient for efficient excitation and high quantum yield for a good signal-to-noise ratio. 

There are a number indicators (most pH probes) which display changes in the absorption spectra on the complexation, but do not display useful fluorescence/51 In this case the change in absorbance is due to different extinction coefficients for the free and complexed forms. Because absorbance is proportional to the probe concentration, Eq. (10.11) can be expressed by... 

Ionization of the phenol hydroxyl group in tyrosine shifts the 277-nm absorption peak to 294 nm and the 223-nm peak to 240 nm. The molar extinction coefficient for the peak of the lower energy band increases from about 1350 M l cm-1 to about 2350 M em-1 and for the higher energy band from about 8200 M cm-1 to about. 1,000 M l cm-1.113 141 In addition, the lower energy absorption band of tyrosine shows vibrational structure that is lost upon ionization of the phenol side chain. 

As soon as the protein is activated with the heterobifunctional crosslinker, the extinction coefficient determined for pure Amb a 1 no longer applies because the heterobifunctional crosslinker absorbs at 280 nm. At this step in the production of AIC, the manufacturing overhead cost requires the use of a fast protein assay, whereas the exact stoichiometry of the subsequent reaction dictates the use of an accurate and precise method. Hence we developed a new extinction coefficient for the activated protein based on experimental data and demonstrated that within the normal activation range of 9 to 12 crosslinkers per Amb a 1, the new extinction coefficient remained constant. The concentration of the purified activated Amb a 1 determined by this direct absorbance A280 method is more precise and accurate than could be assigned by a colorimetric assay. Consequently, the activated Amb a 1 concentration allows for the accurate addition of 1018 ISS required to consistently produce AIC with optimal activity. 

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