Classification of Organic Pigments

Publications have over the course of the years proposed several classification systems for organic pigments. Basically, it seems appropriate to adopt a classification system by grouping pigments either by chemical constitution or by coloristic properties. Strict separation of the two classification systems is not very practical, because the categories tend to overlap however, for the purposes of this book it is useful to list pigments according to chemical constitution. 

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Normal-phase sorbents such as silica and Florisil are used to isolate low to moderate polarity species from nonaqueous solutions. Examples of applications include lipid classification, plant pigment separations, and separations of fat-soluble vitamins from lipid extracts, as well as the clean-up of organic solvent concentrates obtained from a previous SPE method or liquid-liquid extraction. Alumina is used to remove polar species from nonaqueous solutions. Examples include vitamins in feeds and food and antibiotics and other additives from feed. Normal-phase chromatography has been used for a number of years, and most applications for normal-phase column chromatography may be easily transferred over to normal-phase SPE. 

L. Prieur, S. Sathyendranath (1981). An optical classification of coastal and oceanic waters based on the specific spectral absorption curves of phytoplankton pigments, dissolved organic matter, and other particulate materials. Limnol. Oceanogr., 26, 671-689. 

Classification Monoazo color organic pigment Definition Barium salt of D C Red No. 8 Empirical C17H12CIN2O4S ViBa Properties Powd. odorless insol. in water, most soivs. m.w. 444.46 Toxicology TSCA listed... 

Here, pigments and dyes are both important. There is an enormous range of organic dyes available, and a number of classification methods have been used, but that based on the electronic nature of the transition is most relevant here [1]. 

Directive 1999/45/EC, amending Directive 88/379/EEC, will be enacted by the EU member states from 30 July 2002. There is no provision for a transition period. This new Directive introduces the hazard classification dangerous for the environment for preparations, which was previously only required for dangerous substances. Organic pigments are generally not toxic to aquatic organisms because of their limited bioavailability and therefore do not normally require classification. 

Lipoids as a type are non-saponifiable, although some of the sterols may occur as esters with aliphatic acids. A systematic classification of the lipoids is unsatisfactory, since the only common property of these compounds is the physical one of solubility in certain organic solvents. Examples of biological lipoids occur in the essential or volatile oils of plants and the fat-soluble pigments (lipochromes) of plants and animals. In addition, some of the vitamins and the hormones belong to the lipoid type, in that they are fat-soluble. 

Early in the twentieth century, the chemical industry was considered to have two parts the manufacture of inorganic chemicals and the manufacture of organic chemicals. Today, the Standard Industrial Classification (SIC Index) of the United States Bureau of the Census defines Chemical and Allied Products as comprising three general classes of products (1) basic chemicals such as acids, alkalis, salts, and organic chemicals (2) chemicals to be used in further manufacture such as synthetic fibers, plastics materials, dry colors, and pigments and (3) finished chemical products to be used for ultimate consumer consumption as architectural paints, drugs, cosmetics, and soaps or to be used as materials or supplies in other industries such as industrial paints, adhesives, fertilizers, and explosives. An even broader description that is often considered is that of the chemical... 

Color Additives. The FDA has created a unique classification and strict limitations on color additives (see also CoLORANTS FOR FOOD, DRUGS, COSMETICS, AND MEDICAL DEVICES). Certified color additives are synthetic organic dyes that ate described in an approved color additive petition. Each manufactured lot of a certified dye must be analyzed and certified by the EDA prior to usage. Color lakes are pigments (qv) that consist of an insoluble metallic salt of a certified color additive deposited on an inert substrate. Lakes are subject to the color additive regulations of the EDA and must be certified by EDA prior to use. Noncertifted color additives requite an approved color additive petition, but individual batches need not be EDA certified prior to use. 

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