Identification, synthesis, and quantification of a novel carbazole derivative as an impurity in the anthraquinone dye Ext. D&C Violet No. 2 (Acid Violet 43). (April 2022)

• Record Type: Journal Article
• Authors: Weisz, Adrian; Lazo-Portugal, Rodrigo; Perez-Gonzalez, Marianita; Ridge, Clark D.
• Is Part Of: Dyes and pigments. Volume 200(2022)
• Publication Date: 2022-04
• Subjects: Acid Violet 43 (CI 60730) -- Color additive ext. D&C violet No. 2 -- 6-hydroxy-9-methoxy -- 5H-naphtho[2, 3-a]carbazole-5, 13(12H)-dione-11-sulfonic acid (AV43C) -- High-speed countercurrent chromatography -- Sulfonated phthaloyl-carbazole synthesis -- HPLC/UHPLC; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2022.110161
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: The anthraquinone anionic dye Acid Violet 43 (AV43, Colour Index No. 60730) is certifiable in the United States as Ext. D&C Violet No. 2 (EV2) for use as a color additive in externally applied cosmetics. The dye is also permitted in cosmetics in the European Union, Japan, and other countries. To be certified in the U.S., the dye may not contain more than 1% subsidiary colors. The present work was aimed at identifying an impurity, presumed to be a subsidiary color, found in batches of AV43 submitted for certification as EV2. The concentration level of the impurity in a sample of EV2 was enriched from ∼5.5% to ∼33%, and the enriched sample, 260 mg, was subjected to high-speed countercurrent chromatography (HSCCC). The resulting 50.7 mg of the isolated impurity was sufficient for its identification by spectroscopic methods as the sulfonated phthaloyl-carbazole derivative 6-hydroxy-9-methyl-5H-naphtho[2, 3-a]carbazole-5, 13(12H)-dione-11-sulfonic acid (AV43C). That previously unreported compound was synthesized (0.5 g) for use as a reference material to quantify the impurity in batches of EV2. Test portions of 29 batches, produced by 11 manufacturers from six countries, were analyzed by HPLC and UHPLC. The levels of AV43C ranged from <0.05% to 5.66% across batches. Carbazolization through an intramolecular Scholl-type reaction in the sulfonation step of the manufacturing process is suggested as the likely source of AV43C formation. Control of the conditions that enable carbazolization is proposed as a way to reduce or eliminate contamination by AV43C. Highlights: Anthraquinone dye Acid Violet 43 impurity isolated by countercurrent-chromatography. Impurity identified as novel compound, a sulfonated phthaloyl-carbazole (AV43C). AV43C synthesized for use as a reference material. AV43C quantified in 29 batches of the cosmetic dye Ext. Violet No. 2. Source of AV43C contamination during dye manufacture proposed.