1.1.1. Nomenclature

Auramine

• Chem. Abstr. Serv. Reg. No.: 492–80–8
• CAS Name: 4,4′-Carbonimidoylbis[N, N-dimethylbenzenamine]
• Synonyms: C.I. 41000B; C.I. Solvent Yellow 34; 4,4′-dimethylaminobenzophenonimide; 4,4′-(imidocarbonyl)bis(N, N-dimethylaniline); glauramine; Solvent Yellow 34; yellow pyoctanine

Auramine hydrochloride

• Chem. Abstr. Serv. Reg. No.: 2465–27–2
• CAS Name: 4,4′-CarbonimidoylbisN, N-dimethylbenzenamine], hydrochloride (1:1)
• Synonyms: Auramine chloride; 4,4′-carbonimidoylbis[N, N-dimethylbenzenamine], monohydrochloride; C.I. 41000; C.I. Basic Yellow 2; C.I. Basic Yellow 2, monohydrochloride

Michler’s base

• Chem. Abstr. Serv. Reg. No.: 101-6-1
• CAS Name: 4,4′-Methylenebis(N, N-dimethyl)benzenamine
• Synonyms: 4,4′-methylenebis(N, N-dimethyl) aniline; tetramethyldiaminodiphenylmethane; 4,4’-bis(dimethylamino) diphenylmethane; tetra base; methane base; Michler′s hydride; Michler′s methane
• Use: 4,4′-Methylenebis(N,N-dimethyl)benzenamine (Michler′s base) is an intermediate in the synthesis of several organic dyes, e.g., auramine.

Michler’s ketone

• Chem. Abstr. Serv. Reg. No.: 90-94-8
• CAS Name: Bis[4-(dimethylamino)phenyl]methanone.
• Synonyms: 4,4′-bis(dimethylamino)benzophenone;
• p,p′-bis(dimethylamino)benzophenone; bis[p-(N,N′-dimethylamino)phenyl]ketone; tetramethyldiaminobenzophenone
• Use: Bis[4-(dimethylamino)phenyl]methanone (Michler’s ketone) is a chemical intermediate used in the synthesis of a number of dyes and pigments, particularly auramine derivatives. It is a hydrolysis product of auramine.

1.1.2. Structural formula, molecular formula, and relative molecular mass

Auramine

Auramine hydrochloride

Michler’s base

Michler’s ketone

1.1.3. Chemical and physical properties of the pure substance [hydrochloride salt]

• Description: Yellow needles from water (Lide, 2008)
• Melting-point: 267 °C (Lide, 2008)
• Solubility: Slightly soluble in water (Lide, 2008); 10 mg/ml in water; 20 mg/ml in ethanol; 60 mg/ml in ethylene glycol methyl ether (Green, 1990)

1.1.4. Technical products and trade names

Trade names for auramine include: Auramine Base; Auramine N Base; Auramine O Base; Auramine OAF; Auramine OO; Auramine SS; Baso Yellow 124; Brilliant Oil Yellow; Orient Oil Yellow 101; and Waxoline Yellow O.

Trade names for auramine hydrochloride include: ADC Auramine O; Aizen Auramine; Aizen Auramine Conc. SFA; Aizen Auramine OH; Aizen Auramine OW 100; Arazine Yellow; Auramine 0–100; Auramine A1; Auramine Extra; Auramine Extra 0–100; Auramine Extra 0–125; Auramine Extra Cone. A; Auramine FA; Auramine FWA; Auramine II; Auramine Lake Yellow O; Auramine N; Auramine O; Auramine ON; Auramine OO; Auramine OOO; Auramine OS; Auramine Pure; Auramine SP; Auramine Yellow; Basic Flavine Yellow O; Basic Light Yellow; Basic Light Yellow O; Basic Yellow 2; Basic Yellow O; Basonyl Yellow 120; Calcozine Yellow OX; Flexo Yellow 110; and Mitsui Auramine O.

1.1.5. Analysis

Analytical studies on auramine began in the 1970s and continued during the 1980s, by use of high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) to assess auramine levels in shrimp tissue and biological dyes, respectively. Analyses conducted since 1990 use the more sensitive HPLC and mass-spectrometric methods. Table 1.1 presents selected methods of detection and quantification of auramine in various matrices.

Table 1.1.

Selected methods of analysis of auramine in various matrices.

1.2.1. Production

The diphenylmethane dyes are usually grouped with the triarylmethane dyes. The dyes of the diphenylmethane subclass are ketoimine derivatives, and include auramine O (hydrochloride salt). These dyes are still used extensively for the colouration of paper and in the preparation of pigment lakes (Thetford, 2000).

Auramine and its salts can be manufactured by first heating 4,4’-bis(dimethylaminodiphenyl)methane (Michler’s base; CAS No. 101-61-1) with a mixture of urea, sulfamic acid, and sulfur in ammonia at 175°C. The auramine sulfate formed in the reaction may be used directly in the dyeing process or can be converted into auramine base or auramine hydrochloride (auramine O). Highly concentrated solutions for use in the paper industry can be prepared by dissolving auramine base in formamide containing sodium bisulfate. The nitrate and nitrite salts exhibit excellent solubility in alcohols, which facilitates their use in lacquers and flexographic printing colours (Kirsch et al. 1978; Thetford, 2000).

Production of auramine took place first in Europe (Switzerland, Germany, United Kingdom, France), and later also in the USA. Production in the locations has generally been discontinued. Auramine manufacturing is currently mainly located in India and China.

In 1993, approximately 9000 tonnes of basic diphenylmethane and triphenylmethane dyes were sold. Crystal violet, methyl violet, malachite green, auramine, and Rhodamine B are suitable for many purposes and are among the economically most important dyes. Auramine O and its ethyl homologue, ethylauramine, are brilliant yellow dyes with high colour strength. Worldwide annual sales of the dyes are approximately 1000 tonnes (Gessner & Mayer, 2000).

Information was collected from 1996 to 1998 in Europe for the IUCLID database for substances with a production or import volume between 10 and 1000 tonnes/year (Low Production Volume Chemicals (LPVCs)). Auramine hydrochloride was included on the list of LPVCs (Allanou et al., 1999; European Commission, 2008).

The USEPA (2003, 2007) Inventory Update Rule regulation requires manufacturers and importers of certain chemical substances listed in the TSCA Chemical Substance Inventory to report manufacturing information (aggregate production volumes) for chemicals manufactured (including those imported) in amounts of 10 000 pounds or greater (in 1986) or 25 000 pounds or greater (in 2003) at a single site. Table 1.2 presents the aggregate production volumes that were reported for auramine hydrochloride.

Table 1.2.

Auramine hydrochloride production volumes.

Available information indicates that auramine was produced and/or supplied in research quantities in the following countries: Hong Kong Special Administrative Region, India, the People’s Republic of China, and the USA (Chemical Sources International, 2008).

Available information indicates that auramine hydrochloride was produced and/or supplied in research quantities in the following countries: Canada, Germany, Hong Kong Special Administrative Region, India, Japan, the Netherlands, Switzerland, the United Kingdom, and the USA (Chemical Sources International, 2008).

1.2.2. Use

Auramine dyes are used for dyeing of leather, jute, tanned cotton, and paints, and as dye components in inking ribbons, ballpoint pastes, oils and waxes, and carbon paper. The most important areas of application are in dyeing paper and in flexographic printing. For the latter, a large number of salts are produced, which have a high solubility in ethanol and ethanol-water mixtures (e.g. nitrates, nitrites, bromides, iodides, salts of alkyl-, aralkyl-, or arylsulfonic acids, thiocyanates, and phosphates). For dyeing paper, solutions of the hydrochloride in organic solvents (e.g., thiodiglycol) are employed, and tartaric and citric acids have been used as stabilizers. The chlorides can also be converted into more easily soluble acetates or propionates to obtain highly concentrated solutions. The hydrogen sulfates of auramine are also readily soluble. Coloured salts based on auramine with tannic acid, phosphomolybdic acid, and preferably phosphotungstomolybdic acid are used as yellow toner pigments for the development of latent electrostatic images (Fierz-David & Blagey, 1949; Gessner & Mayer, 2000; Thetford, 2000; Varella et al., 2005).

Auramine was used as a fluorescent staining agent to stain acid-fast bacteria in sputum or infected tissue, and also in combination with the dye rhodamine in the Truant auramine-rhodamine stain for Mycobacterium tuberculosis (Silver et al., 1966).

Auramine was historically used as a component in brilliantine, a grooming product intended to soften men’s hair (Gubéran et al., 1985), particularly in the 1930s, which could have resulted in occupational exposure as well as customer exposure to auramine.

Auramine has also been used in some countries as a food colourant (D’Aquino & Santini, 1977). Auramine has been detected in a small percentage of food samples from India (Tripathi et al., 2007), including fresh peas (Rao & Bhat, 2003). In China, auramine has been detected in bean products (Lin, 2007).

Auramine has been used to colour smoke, in military applications (Department of the Army, 1990) and in firework displays (Shimizu, 1981).

1.3.1. Natural and environmental occurrence

Auramine is not known to occur as a natural product.

No data have been reported on levels of auramine in environmental matrices such as water and soil.

1.3.2. Occupational exposure

The US National Occupational exposure survey (1981-1983) estimated that about 19 000 workers were exposed to auramine. The industries with the largest numbers of exposed workers included the paper and allied products industry, and the health services industry (laboratory workers) (NIOSH, 1990).

The only well-described groups of workers exposed to auramine include British (Case & Pearson, 1954) and German auramine production workers (Kirsch et al., 1978; Thiess et al., 1982). Case reports of bladder cancer among Swiss auramine-production workers have also been published (Müller, 1933). Among a cohort of 4772 laboratory workers, 8% were reported to have been exposed to auramine and its salts (Kauppinen et al., 2003). Exposure measurements in the workplace or biological samples of workers employed in the production of auramine are not available.

The manufacture of auramine involves potential exposure to its process chemicals (e.g., dimethylaniline, formaldehyde, sulfur, ammonium chloride, ammonia, Michler’s base), as well as to other chemicals used and produced at the same location (e.g., benzidine, 1-naphthylamine, 2-naphthylamine, magenta, aniline) (Case & Pearson, 1954).

1.4.1. Auramine

(d) Other

(i) GESTIS

Table 1.3 presents some international limit values for auramine (GESTIS, 2007).

Table 1.3.

International limit values (2007) for auramine.

1.4.2. Michler’s Base [CAS No. 101-61-1]

(e) Other

(i) GESTIS

Table 1.4 presents some international limit values for Michler’s base (GESTIS, 2007).

Table 1.4.

International limit values (2007) for Michler’s base.