466 JOURNAL OF COSMETIC SCIENCE raw materials and manufacturing processes need to be harmonized between countries. For example, chlorophylls should be obtained from alfalfa in the United States, and the permitted origin should be an edible plant in the European Union and a green plant in Korea. Third, restrictions on permitted extraction solvents and their residual solvent concentrations need to be harmonized in the specifications as well. STANDARDIZATION CHALLENGES IN THE NOMENCLATURE OF SYNTHETIC COLORANTS Each country has its own version of nomenclature for colorants. Confusion arises when labeling the salts or lakes of synthetic colorants. Here, we present the different labeling system developed by each country according to the rules of its nomenclature. The list of official names for synthetic colorants are found in Regulation 21 CFR, Parts 74, and 82 for the United States and in Annex IV of Regulation (EC) No. 1223/2009 for the EU. Specifically, a CI number is used in the EU. This has a five- or six-digit number based on the chemical composition. In total, 34 categories of chemical groups have been identified (102). Among them, the nine categories shown in the Table X encompass the synthetic colorants used in cosmetics. Some of the organic colorants have same dye and differ only in the metal used for salt formation. For example, Lithol Rubine B (CI 15850, D&C Red No. 6) is a sodium salt, and Lithol Rubine BCA (CI 15850, D&C Red No. 7) is a calcium salt. In the EU, these colorants with different metal ions for salt formation are not distinguished by the INCI name as they are assigned the same CI number (103). However, colorants with different metal ions are distinguished in their labeling in the United States and Korea (as discussed in the next section). METAL SALT PIGMENTS When sodium salt dye replaces a sodium cation in alkaline earth (e.g., calcium, strontium or barium) or transition metals (e.g., manganese), it leads to high insolubility, sometimes Table X CI Numbers Used in Synthetic Colorants by Chemical Group Chemical Group CI Number Nitroso CI 10000–10299 Nitro CI 10300–10999 Azo CI 11000–19999 (mono) CI 20000–29999 (di) Triarylmethane CI 42000–44999 Xanthene CI 45000–45999 Quinoline CI 47000–47999 Anthraquinone CI 58000–72999 Indigos CI 73000–73999 Phthalocyanine CI 74000–74999 Adapted from Society of Dyers and Colourists (102).

467 COSMETIC COLORATION: A REVIEW with different shades of colors (104). For this reason, the United States and Korea have assigned individual names to these colorants. Depending on each country’s regulations, a particular salt form may not be permitted. Therefore, when a synthetic colorant is identified only by the CI number, it is necessary to confirm the metal ion of the dye. For instance, Lithol Reds (CI 15630) is known as the azo dye that has a different shade of red by the metal ion, from a yellowish red (sodium salt: Lithol Red) to a strong blue shade red (barium salt: Lithol Red BA Figure 20) (104,105). If this colorant is imported from the EU to Korea, its labeling name is reassigned based on the metal ion: sodium salt for Red 205, barium salt for Red 207, calcium salt for Red 206, and strontium salt for Red 208. Lithol Rubine BCA (CI 15850), which is the calcium salt of Lithol Rubine B, is virtually insoluble in water, but Lithol Rubine B (sodium salt) has limited solubility in water. Another azo dye, Permanent Reds (CI 15865) is a red colorant ranging from bright orange (sodium salt: Permanent Red 2B) to bluish-red (calcium salt: Permanent Red F5R Figure 20) (105). In Korea, only the calcium salt form, Red 405, is permitted. Triarylmethane dye has two salt forms: the blue sodium salt form Brilliant Blue FCF (CI 42090, FD&C Blue No. 1) and the greenish-blue ammonium salt form Alphazurine FG (CI 42090, FD&C Blue No. 4 Figure 20). In addition, xanthene dyes that have different types of salt forms are distinguished by the nomenclature. Xanthene dyes are combined with alkali metal cations (e.g., sodium, Figure 20. Salt forms of azo and triarylmethane dyes.