Colored molecules

Other early work, which continues to this day, involved vibronic relaxation [6] of large colored molecules such as chrysene [19], pyrene [20] and perylene [21], due to the relative ease of using visible or near-UV light to pump and probe these systems (see example C3.5.6.5 below). 

In Pedersen s early experiments, the relative binding of cations by crown ethers was assessed by extraction of alkali metal picrates into an organic phase. In these experiments, the crown ether served to draw into the organic phase a colored molecule which was ordinarily insoluble in this medium. An extension and elaboration of this notion has been developed by Dix and Vdgtle and Nakamura, Takagi, and Ueno In efforts by both of these groups, crown ether molecules were appended to chromophoric or colored residues. Ion-selective extraction and interaction with the crown and/or chromophore could produce changes in the absorption spectrum. Examples of molecules so constructed are illustrated below as 7 7 and 18 from refs. 32 and 131, respectively. 

Why are some organic compounds colored while others aren t /3-Carotene, the pigment in carrots, is purple-orange, for instance, while cholesterol is colorless. The answer involves both the chemical structures of colored molecules and the way we perceive light. 

Also bound to the UV-Vis spectral area is fluorescence spectrometry. It is most important with respect to those fluorescent food colorants that have been incorporated into food. In detail it helps to (1) identify a colorant by the spectral pattern of fluorescence excitation and emission spectra, (2) quantify its concentration by the fluorescence emission intensity, (3) qualify the enviromnent into which the colorant molecule is embedded, and (4) perform structural research on the food matter into which the colorant is incorporated. 

To qualify the environment into which the colorant molecule is embedded, the actual fluorescence spectrum is compared with the one under standard conditions. If the fluorescence emission spectrum is shifted to longer wavelengths (bathochromic shift), it can be concluded that the molecular enviromnent is of a more polar nature or is polarized by the excited fluorophore. Conversely, a fluorescence shift to shorter wavelengths (hypsochromic shift) indicates a transfer of the fluorophore from a polar... 

A sequential analysis protocol includes three steps (1) extraction in water or other appropriate solvent for the colorant, (2) purification or concentration of the colorant, and (3) separation coupled with detection of the target molecule. Different methods of extracting synthetic colorants from foods have been developed using organic solvents followed by SPE protocols using as adsorption support RP-C18, amino materials, or Amberlite XAD-2. Eor qualitative evaluations, the easiest option for separating colorant molecules from unwanted ingredients found in an extract is SPE on polyamide or wool. 

Spectrophotometric resolution for the discrimination of individual colorant molecules found in mixtures is lower than that of chromatographic techniques such as TLC or HPTLC and even low-cost paper chromatography. More expensive but more accurate determinations may be made by RP-HPLC, IP-HPLC with UV-Vis, and diode array detection. ... 

Dye release developers are themselves colored molecules, the presence of which in silver halide photographic materials could interfere with light capture by the light-sensitive silver halide. Less light would be available to the sensitizing dyes. Another approach has been reported in which the leuco dye is linked to the coupling-off position of conventional photographic color... 

There are two types of colored molecule that are used in the toner, namely the colorant and the charge control agent (CCA). The colorant is used to impart color to the toner whereas the CCA is used to help impart and especially control the triboelectric charge on the toner particles. 

Dyes are colored molecules that can form covalent bonds to fabric. For example, Procion Brilliant Blue M-R is a dye with a blue chromophore (the colored part) attached to a reactive dichloro-triazine ring ... 

McGuire, S. and Yuan, F. (2001) Quantitative analysis of intratumoral infusion of color molecules. Am. J. Physiol., 281, H715-H721. 

We know that individual molecules move because we can see the collection of food coloring molecules spread thoughout the glass of water. The water is a pale color because each food coloring molecule is surrounded by colorless water molecules. 

Open a bottle of vanilla extract. How long does it take before you can smell it Some of the vanilla extract molecules move from the bottle to your nose. These molecules move through the air faster than the food coloring molecules move through the water. 

Molecules are always moving. The food coloring molecules spread out through the water. This type of movement is called diffusion. The diffusion of the food coloring molecules makes the water take on an even color. 

Pigment Any colorful molecule chlorophyll is the dominant pigment in most plants. 

The occurrence of the reverse effect - namely one in which a previously uniformly coloured volume of water clears itself and reverts to just having a small region (of volume) in which is contained a high concentration of the colorant molecules, whilst the main volume of the water has become completely clear - is never observed in our experience of natural phenomena This kind of paradox was pointed out by Boltzmann. Its rationalisation is based on the fact that ... 

The relationship between the internal-age and external-age distribution can be demonstrated by analyzing a continuous reactor operating at steady state that is filled with material of volume V. Consider again that the volume of reactor is filled with maize-colored molecules, and at time t = 0 we start to inject blue molecules to replace the maize molecules. By definition of /(a), the volume of molecules inside the reactor that have been there between a time a and cr + da is... 

Many colored molecules can be described as donor-acceptor chromophores. In such cases, the longest-wavelength absorption depends on the extension of the conjugated system and on the amount of bond length equalization which is... 

Bleach removes stains from clothing by oxidizing colored molecules to form colorless molecules. 

Dye-Based Systems Many compounds can be used [lh,i]. Classical examples are found in the numerous available dyes and colored molecules [li] such as xanthenic dyes (Rose Bengal, eosin [194,195], etc.), thiazines (methylene blue, etc.), acridines, /V-methylacridone, phenosaffanines, thiopyronines, riboflavines [196,197], pheno-xazines [198], pyrromethenes [199], polymethines, fluorones, squarylium [200], julolidine dyes, and so on. (see, for example, Rose Bengal, acriflavine, and acridine orange in (10.57)). 

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