Color dyeings

In the DPD colorimetric method for the free chlorine residual, which is reported as parts per million of CI2, the oxidizing power of free chlorine converts the colorless amine N,N-diethyl-p-phenylenediamine to a colored dye that absorbs strongly over the wavelength range of 440-580 nm. Analysis of a set of calibration standards gave the following results... 

Spectral Sensitization. Photographic silver haHde emulsions ate active with light only up to about 500 nm. However, theh sensitivity can be extended within the whole visible and neat-H spectral region up to about 1200—1300 nm. This is reached by the addition of deeply colored dyes that transfer excited electrons or excitation energy to the silver haHde. 

The photolysis of polyhalogenated compounds forms the basis for another monochrome system. Iodoform can undergo photolysis to produce hydrogen iodide, which subsequendy reacts with a di(2-furfuryl) derivative (3) and aromatic amines to produce a colored dye adduct (4) (29). The photolysis scheme and subsequent reactions can be shown by the following ... 

Because of the time and expense involved, biological assays are used primarily for research purposes. The first chemical method for assaying L-ascorbic acid was the titration with 2,6-dichlorophenolindophenol solution (76). This method is not appHcable in the presence of a variety of interfering substances, eg, reduced metal ions, sulfites, tannins, or colored dyes. This 2,6-dichlorophenolindophenol method and other chemical and physiochemical methods are based on the reducing character of L-ascorbic acid (77). Colorimetric reactions with metal ions as weU as other redox systems, eg, potassium hexacyanoferrate(III), methylene blue, chloramine, etc, have been used for the assay, but they are unspecific because of interferences from a large number of reducing substances contained in foods and natural products (78). These methods have been used extensively in fish research (79). A specific photometric method for the assay of vitamin C in biological samples is based on the oxidation of ascorbic acid to dehydroascorbic acid with 2,4-dinitrophenylhydrazine (80). In the microfluorometric method, ascorbic acid is oxidized to dehydroascorbic acid in the presence of charcoal. The oxidized form is reacted with o-phenylenediamine to produce a fluorescent compound that is detected with an excitation maximum of ca 350 nm and an emission maximum of ca 430 nm (81). 

Miscellaneous Uses. Inks used by inspectors to stamp the grade or quaUty on meat must, bylaw, be made from food-grade colors. Dyes used in packaging materials that come in direct contact with a food must also be food-grade or, if not, it must be estabUshed that no part of the colorant used migrates into the food product. Pet foods, too, if colored, must contain only those colorants recognized by the FDA as suitable for the purpose. 

Liquid-penetrant examination involves wetting the surface with a fluid which penetrates open cracks. After the excess liquid has been wiped off, the surface is coated with a material which vidll reveal any liquid that has penetrated the cracks. In some systems a colored dye will seep out oi cracks and stain whitewash. Another system uses a penetrant that becomes fluorescent under ultraviolet hght. 

The improved design of the gating interface resulted in precise alignment of the two capillaries. A colored dye solution was added to the HPLC eluent to allow for du cct observation of the flow gating and injection processes. Through observation of the movement of the dye through the interface, it was possible to ensure that the electrokinetic injections were performed correctly. Troubleshooting had been a... 

Anfarbbarkeit, /. colorability, dyeability. anf lrben, v.t. color, dye. paint, tint, tinge ... 

Brauntran, m. (Leather) Uubber, thick cod oil. Braunung, /. browning brown coloring dyeing brown bronzing. 

Farbe,/. color dye pigment stain paint hue, tint (Leather) weak ooze, also a container for it (Lead) skimminga. 

Tracer materials are defined as any product included in the test substance that can be recovered analytically for determining the drift from the application. This may be the active ingredient in an actual tank mix, or it may be a material added to the tank mix for subsequent detection. The selection of an appropriate tracer for assessing deposition rates in the field is critical to the success of a field study. Tracer materials such as low-level active ingredient products, colored dyes, fluorescent dyes, metallic salts, rare earth elements and radioactive isotopes have been used with varying degrees of success in the field. An appropriate tracer should have the following characteristics ... 

Dye solubility test A colored dye soluble in only one component is added to the emulsion. If the color spreads throughout the whole emulsion, the phase in which the dye is soluble is the continuous phase. 

After products are produced by refining they are further enhanced in a blending unit. In this unit the finished products are made by mixing the components in blending tanks. To gasoline for example, coloring dyes or special additives maybe added. The completed blends are tested and then routed to tank farm storage or shipment. 

Indicator displacement assays (IDAs) - or, in the specific case of fluorescent indicators, F-IDAs - are based on the next alternative concept described here. A receptor with an affinity for a given analyte is loaded with an indicator, usually a fluorescent or colored dye, whose spectral properties undergo a change upon complexation with the receptor. Treatment of this indicator-receptor complex with the analyte results in the displacement of the indicator from the receptor and a restoration of the indicator s original spectral properties, indirectly reporting analyte coordination (Fig. 27). For effective detection, two main requirements have to be fulfilled (1) the receptor/indicator interaction must be reversible and weaker than the interaction of the receptor with the designated analyte and (2) the indicator must show significantly different optical properties when bound to the receptor and when freely dissolved in solution. 

---