Extinction coefficient, maximum molar

Abbreviations A.max is the wavelength of maximum absorption in nanometers is the extinction coefficient or molar absorptivity (units are not necessary) and sh is the shoulder. The wavenumber, V, in reciprocal micrometers, might also be given. 

A typical UV spectrum is that of 2-methyl-l,3-butadiene (isoprene), shown in Figure 14-15. The position of a peak is defined by the wavelength at its maximum, a Ani x value (in nanometers). Its intensity is reflected in the molar extinction coefficient or molar absorptivity, e, that is characteristic of the molecule. The value of e is calculated by dividing the measured peak height (absorbance, A) by the molar concentration, C, of the sample (assuming a standard cell length of 1 cm). 

A-T ax are the spectral maximum of UV-Vis absorption, emission, and triplet state absorption, respectively, is the molar extinction coefficient, ta and Tt, Oa and r, s and Et, are the lifetime, quantum yield, and energy content of the singlet and triplet excited states of RF, respectively. 

Most often, quantification has been carried out by exclusively assessing the absorption at the maximum wavelength and selection of the appropriate molar extinction coefficient. " Reasonable values will be obtained if the absorption at 600 to 650 nm is subtracted. 

The UV absorption spectra of niclosamide in methanol, methanolic 0.1 N HC1 and methanolic 0.1 N NaOH are shown in Fig. 3. The figures were recorded using a Perkin-Elmer double beam model 550s UV-Vis spectrophotometer. The values of the log emax (log molar extinction coefficient) at their corresponding wavelength maximum in nanometers (2max) are shown in the following table. 

The fluorescent properties of NHS-fluorescein are similar to FITC. The wavelength of maximal absorbance or excitation for the reagent is 491nm and its emission maximum is 518nm, exhibiting a visual color of green (Sheehan and Hrapchak, 1980). Its molar extinction coefficient at 491 nm in a pH 8.0 buffer environment is Other components in... 

AMCA-hydrazide has a maximal excitation wavelength of 345 nm and a maximum emission wavelength in the range of 440-460 nm. A solution of AMCA in PBS at a concentration of 16.7ng/ml (71.61 nmoles/ml) gives an absorbance at 345 nm of about 1.28. This translates into a molar extinction coefficient at this wavelength of about 13,900M em-1. Different solvents and conditions may alter this value somewhat. 

All measurements are done in CH2C12. Molar extinction coefficients are shown in parentheses where reported and are given as 10 i. Shoulder = sh on maximum. When shoulder is given in parentheses, the shoulder is not clearly discemable from the major peak. 

The electronic spectrum of the fractions containing the pure tridehydro [18]annulene exhibits the strongest absorption maximum (in benzene) at 342 nm. (e 155,000) and the spectroscopic yield, based on the molar extinction coefficient, is 1.17 g. (2.40% from 1,5-hexadiyne). The yield of tridehydro[18]annulene in the mixed fractions, based on the 342 nm. maximum,is 0.27g.(0.55%). The tridehydro [18]annulene is best stored in solution in the refrigerator. 

The resulting extinction coefficient remained constant within the accuracy of the measurements. In the transition from monoazo to disazo pigment, however, the value of the maximum molar extinction coefficient is more than doubled, because the effect of the two azo linkages is enhanced by additional interaction via the diphenyl moiety. This, however, does not improve the conjugation the shade does not shift remarkably ... 

Pigment solution Maximum molar extinction coefficient (in 104 L/mol cm)... 

Fig. 13.4 Chemical structure, absorption maximum and molar extinction coefficient of typical algal mycosporine-like amino acids (MAAs) and cyanobacterial scytonemin...

The strong absorptions of the complex technetium (IV) hexahalides (Fig. 10) can also be utilized for spectrophotometric determinations. A sensitive method has been developed using hexachlorotechnetate (IV) When pertechnetate is heated for 50- 0 min in cone, hydrochloric acid, it is reduced to the complex [TcClgp . The absorption curve of [TcClgf in cone. HCl has a maximum at 338 nm where technetium can be determined in the presence of microgram amounts of rhenium or molybdemun. The molar extinction coefficient is said to be 32.000 (after Jorgensen and Schwochau it amounts to 10.600). About 0.1 fig Tc/ml can be determined. Rhenium present in quantities up to 30 ng/ml has almost no influence on the determination of technetium. The error in the determination of the latter in the presence of molybdenum at a weight ratio of 1 1 is 1-2%. 

This amount of thiocyanate is sufficient for both complete reduction and complex formation. Reduction is allowed to proceed for 30 to 45 s after the addition of the thiocyanate. A bright red color can readily be observed at a technetium (VII) concentration of 0.1 ng per ml. Acetone (6 ml) is then added and the volume of the solution mixed and adjusted to 10 ml with distilled water. At this point, the color has generally developed to less than 50% of its final intensity. Quartz 1-cm glass-stoppered cells are filled with the technetiiun solution and placed in a 20 °C water-cooled spectrophotometer. The extinction will approach a maximum intensity in 1 to 3 h. The maximiun extinction occurs at 510 nm with a molar extinction coefficient and standard deviation of 47,500 + 500 in 60 vol. % of the acetone-aqueous medium. An additional examination of the analysis may be carried out by extract-... 

Chlorine dioxide readily degrades in aqueous solutions imder ultraviolet light. It has a broad UV absorption band with a maximum near 360 nm and a molar extinction coefficient of about 1,150 (M X cniy (Aieta and Berg 1986). It is postulated that the reaction in solution proceeds as in the gas phase, to give CIO and O. The initial photodissociation reaction is followed by rapid dark and light reactions to produce the products, chlorate (CIO3 ), hypochlorite (OCl ), and chloride (Cl ) (Zika et al. 

Solutions of isolated dioxiranes, characteristically dimethyldioxirane (DMD) in acetone, possess a pale yellow color, which serves as a convenient analytical index for monitoring the dioxirane consumption in oxidation reactions and kinetic studies. For DMD, the absorption maximum (n-jt transition ) centers at ca 325 nm, with a molar extinction coefficient (e) of 12.5 0.5 M cm in acetone. The alternative and more rigorous analytical method for dioxirane quantification utilizes iodometry (Kl/starch). 

The relations of molar extinction coefficients and oxygen absorption rates, plotted vs. time, are illustrated in Figures 3 and 4 (solvents, benzene and butyric acid, respectively). The variation of coefficients was parallel to the rate of oxygen absorption—i.e. the larger the coefficient, the higher the oxygen absorption rate. It is considered therefore that the catalyst at its maximum absorption coefficient is in a desirable form for oxidizing acrolein. 

From equation (73) it is possible to calculate V from the molar extinction coefficient at the absorption maximum (emax), the band width at half maximum (v,/2) and Eop if the interreactant separation is known. 

In chemistry it is common to indicate the intensity of a spectral band by stating the maximum molar extinction coefficient emax-Usually the shape of the absorption curve is given as a function of the wave number v, and a curve e v) is obtained as given in Figure 5-1. 

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