Maximum absorption wavelength and

Figure 2. Chemical structures of selected photosensitizers. the PDT-relevant maximum absorption wavelength, and e, the corresponding molar absorption coefficient, are indicated. For PF/HPD, ( ) indicates the uncertainty of the chemical structure for these entities.

Table 1. Maximum absorption wavelength and molar extinction coefficient in the UV-visible spectra (CH2CI2) of...

Maximum absorption wavelengths and corresponding molar extinction coefficients of the ferric complexes of PALL, PALO and PADB. The spectral data relative to the model compound ferric complex... 

We always recommend that structural changes occurring after the saponification procedure be verified. Since the hydroxyl groups have no influence on the chromophore, the wavelength of the maximum absorption, shape, and intensity of the ultraviolet-visible (UV-Vis) spectrum would be identical for unsaponified and saponified samples. 

The maximum absorption wavelengths in different solvents of many carotenoids can be found in the literature, and the % III/II values are also available for some carotenoids. It is common to find variations of 1 to 3 nm in for the same carotenoid in the same solvent cited in different publications. No identification based simply on the matching of recorded UV-Vis spectra with tabulated data can be done without considering the relationships of structures and the factors influencing light absorption. The principal factors that influence carotenoid UV-Vis absorption spectra are discussed below. 

To determine the amylose content of starch, the iodine reaction has been most commonly used because amylose and amylopectin have different abilities to bind iodine. The methods such as blue value (absorbance at 680 nm for starch-iodine complex using amylose and amylopectin standards), and potentiometric and amperometric titration have been used for more than 50 years. These procedures are based on the capacity of amylose to form helical inclusion complexes with iodine, which display a blue color characterized by a maximum absorption wavelength (kmax) above 620 nm. During the titration of starch with iodine solution, the amount (mg) of iodine bound to 100 mg of starch is determined. The value is defined as iodine-binding capacity or iodine affinity (lA). The amylose content is based on the iodine affinity of starch vs. purified linear fraction from the standard 100 mg pure linear amylose fraction has an iodine affinity of 19.5-21.0mg depending on amylose source. Amylopectin binds 0-1.2mg iodine per 100mg (Banks and Greenwood, 1975). The amylose content determined by potentiometric titration is considered an absolute amylose content if the sample is defatted before analysis. 

D-Xylose was found to yield 2-furaldehyde almost exclusively, but D-lyxose, D-ribose, and L-arabinose produce another, as yet unidentified, compound absorbing at 289 nm, which is the maximum absorption wavelength for reductic acid. D-Glucose, D-fructose, and sucrose give almost identical yields (—85%) of 5-(hydroxymethyl)-2-fural-dehyde, but D-galactose and D-mannose give much lower yields thereof. 

The synthetic GFP chromophore analogue (2-(4-nitrophenyl)-5-(4-cyanophenyl methylidene) imidazol-4-one ), was synthetized according to ref [6]. It was recrystallized from ethanol and characterized by 1H-NMR through their typical proton signal at 7.1 2 ppm. High concentrated solutions of approximately 3.10 3M were prepared by dissolution in dioxan. The photophysical characteristics of this analogue were determined from the UV absorption spectra and from steady-state fluorescence. An extinction coefficient of 20700 M cm 1 was determined at the maximum absorption wavelength at 406 nm. The fluorescence emission peaks at 508 nm. 

Table 2 Wavelengths of Maximum Absorption (Amax) and Molar Coefficient of Absorption (e) of Aflatoxins...

All attempts (74,89) to find a sensible, quantitative relation between the wavelength of maximum absorption ( max) and typical macroscopic properties of the solvent (i.e., dielectric constant) have so far failed (146). However, the size of the solvent cavity in which the electron is trapped also plays a decisive role (101) in determining the transition energy [Eqs. (2), (3)], and the solvent dependence of A.max might well indicate a variation in cavity size from solvent to solvent. In this spirit, Dorfman and Jou (48) have evaluated cavity radii on the basis of the simple Jortner model for the solvated electron. The values are shown in Fig. 3, which shows a plot of the optical transition energy max versus... 

A major drawback of aryl azides is that their maximum absorption wavelength is below 300 nm, since electromagnetic irradiation at these wavelengths can substantially damage the biological system. Consequently, a large number of substituted aryl azides have been made and evaluated for their absorption... 

The o(m, p)-PBTMS-PPV series shows very similar absorption profiles with those of PMEH-PPV polymers. The maximum absorption wavelengths of o(m)-PBTMS-PPV are blue-shifted for the same reason as that of o(ra)-PMEH-PPV. But PBTMS-PPV polymers show about 20-50 nm blue-shifted absorption maxima compared to those of PMEH-PPV series, because the trimethylsilyl substituent has little electron-donating property. The PL spectra show very drastic changes in emission color because of the substituents and kink effects. Figure 19 shows PL emission profiles of the polymers mentioned above. 

The wavelength of maximum absorption, /.max, and the corresponding max are identifying properties of a compound. Units are normally omitted from specifications of e. 

Absorption spectra of more than five-ring systems are compared in Table XII, where only the first and second (and third) bands are listed for simplicity. Pericondensation (195) to 2 shifts the absorption band more bathochromically than catacondensation (30) does. Cyclization of azonia-pentahelicene salt (180) to the corresponding azoniabenzo[g/n ]perylene salt (204) shifts the maximum absorption wavelength about 18 nm longer, similar to the annelation to form azoniahexahelicene salt (206). 

The separated spots, obtained by subjecting a paprika color standard, after saponification, to CIS TLC under the conditions described above, were then subjected to scanning densitometry. The visible absorption spectra were scanned in the wavelength range of 370-700 nm, and excellent visible absorption spectra were obtained (Fig. 3A). The spectrum of the main spot (Rf=0.50) of the paprika color, after saponification, showed its maximum absorption wavelength at 480 nm, which identically matches the spectrum of the capsanthin standard (Fig. 3C). 

Reflection spectra of the spots on the TLC plates separated under the conditions described above were measured at scanning wavelengths of 370-700 nm. Fig. 4 (right) shows the visible absorption spectra obtained the maximum absorption wavelengths were 435 and 460 nm, being in complete agreement with the visible absorption spectrum for the standard preparation of crocetin. 

Table 1 Wavelengths of maximum absorption (v ), and molar transition energies (Em) for Nile Red dissolved in imidazolium ionic liquids [68]...

TABLE 6.9. Non-anthocyanin Phenolic Compounds Identified by LC/ESI-MS in Wines from Different Vitis Yinifera Varieties (Tempranillo, Garciano, Cabernet Sauvignon, Merlot) with their Principal MS Fragments and the Maximum Absorption Wavelengths of UV-vis Spectra2... 

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