Molar absorptivity coefficient

Only slightly less accurate ( 0.3—0.5%) and more versatile in scale are other titration techniques. Plutonium maybe oxidized in aqueous solution to PuO " 2 using AgO, and then reduced to Pu" " by a known excess of Fe", which is back-titrated with Ce" ". Pu" " may be titrated complexometricaHy with EDTA and a colorimetric indicator such as Arsenazo(I), even in the presence of a large excess of UO " 2- Solution spectrophotometry (Figs. 4 and 5) can be utilized if the plutonium oxidation state is known or controlled. The spectrophotometric method is very sensitive if a colored complex such as Arsenazo(III) is used. Analytically usehil absorption maxima and molar absorption coefficients ( s) are given in Table 10. Laser photoacoustic spectroscopy has been developed for both elemental analysis and speciation (oxidation state) at concentrations of lO " — 10 M (118). Chemical extraction can also be used to enhance this technique. 

This is the fundamental equation of colorimetry and spectrophotometry, and is often spoken of as the Beer-Lambert Law. The value of a will clearly depend upon the method of expression of the concentration. If c is expressed in mole h 1 and / in centimetres then a is given the symbol and is called the molar absorption coefficient or molar absorptivity (formerly the molar extinction coefficient). 

It will be apparent that there is a relationship between the absorbance A, the transmittance T, and the molar absorption coefficient, since ... 

Attention is directed to the fact that the molar absorption coefficient depends... 

The basic principle of most colorimetric measurements consists in comparing under well-defined conditions the colour produced by the substance in unknown amount with the same colour produced by a known amount of the material being determined. The quantitative comparison of these two solutions may, in general, be carried out by one or more of six methods. It is not essential to prepare a series of standards with the spectrophotometer the molar absorption coefficient can be calculated from one measurement of the absorbance or... 

If it is known that the compound obeys Beer s Law the molar absorption coefficient e can be determined from one measurement of the absorbance of a... 

The values of the molar absorption coefficients and e2 can be deduced from measurements of the absorbances of pure solutions of substances 1 and 2. By measuring the absorbance of the mixture at wavelengths Xl and X2, the concentrations of the two components can be calculated. 

Procedure, (a) Determination of molar absorption coefficients and verification of additivity of absorbances. The molar absorption coefficients must be determined for the particular set of cells and the spectrophotometer employed. For the present purpose we may write ... 

Discussion. The titration of a copper ion solution with EDTA may be carried out photometrically at a wavelength of 745 nm. At this wavelength the copper-EDTA complex has a considerably greater molar absorption coefficient than the copper solution alone. The pH of the solution should be about 2.4. 

Whilst nothing can improve upon the disadvantage of low molar absorption coefficients, instrumental designs and improvements with ratio recording and FT-IR instruments have virtually overcome the accuracy and instrumental limitations referred to in (b) and (c) above. As a result, quantitative infrared procedures are now much more widely used and are frequently applied in quality control and materials investigations. Applications fall into several distinct groups ... 

A) The use of a calibration graph. This overcomes any problems created due to non-linear absorbance/concentration features and means that any unknown concentration run under the same conditions as the series of standards can be determined directly from the graph. The procedure requires that all standards and samples are measured in the same fixed-path-length cell, although the dimensions of the cell and the molar absorption coefficient for the chosen absorption band are not needed as these are constant throughout all the measurements. 

Mohr procedure exptl. details of, 349, 351 Molar absorption coefficient 649 Molar conductivity 520 Molar extinction coefficient see Molar absorption coefficient Molar solution definition, 260 Molarity 259 Mole 259... 

Properties of luciferin. The crystals are microscopic needles, which melt with decomposition at 205-210°C (Bitler and McElroy, 1957). It is a quite stable luciferin compared with some other luciferins, such as Cypridina luciferin and the luciferins of krill and dinoflagellates. It is not significantly affected by lOmM H2SO4 and lOmM NaOH at room temperature in air. The absorption spectral data of luciferin are shown in Fig. 1.3 (McElroy and Seliger, 1961). The molar absorption coefficient of the 328 nm peak in acidic solutions and that of the 384 nm peak in basic solutions are both 18,200 (Morton et al., 1969). Luciferin is fluorescent, showing an emission maximum at 537 nm in both acidic and basic conditions, although the intensity of the fluorescence is lower in acidic solution than in basic solution (fluorescence quantum yields 0.62 in basic condition, and 0.25 in acidic condition Morton et al., 1969). The chemical synthesis... 

Fluorescence emission maximum Fluorescence quantum yield Molar absorption coefficient (e) at peak wavelengths (as monomer)... 

Ifi fluorescence intensity k proportionality factor lo intensity of irradiating hght e molar absorption coefficient a amount of substance applied d thickness of adsorbent layer... 

Chromophore Wavelength for Maximum Absorption (nm) Molar Absorption Coefficient at 254 nm... 

Molar absorptivity coefficient, L mol cm-1. d Number of ester groups in the molecule. 

Molar absorption coefficient (2) Dielectric constant ASTM... 

Hendriksen, B. A. Sanchez-Felix, M. V. Tam, K. Y., A new multiwavelength spectrophotometric method for the determination of the molar absorption coefficients of ionizable drugs, Spectrosc. Lett. 35, 9-19 (2002). 

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