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The listed aromatic amines (azocolourants) requirements of the European Regulation (EC) No. 1907/2006 of the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), Annex XVII concerning the Restrictions on the manufacture, placing on the market and use of certain dangerous substances, preparations and articles, Item no. 43, Points 1 and 2.

Summary of the requirements:

Limit

Aromatic amines 30 mg/kg

2 blue colorants 1000 mg/kg

Azo dyes (see their definitions at the bottom of page) are among the oldest man-made chemicals and they are used in the textile, printing and the food industries. Some dyes and some of their N-substituted aromatic bio-transformation products are toxic and/or carcinogenic and therefore these dyes are considered to be hazardous.

Azo dyes which, by reductive cleavage of one or more azo groups, may release in detectable concentrations one or more of the aromatic amines listed in the Directive may not be used in textile and leather articles which may come into direct and prolonged contact with the human skin or oral cavity, including -

(a) clothing, bedding, towels, hairpieces, wigs, hats, nappies and other sanitary items, sleeping bags;

(b) footwear, gloves, wristwatch straps, handbags, purses or wallets, briefcases, chair covers, purses worn round the neck;

(c) textile or leather toys and toys which include textile or leather garments; and

(d) yarn and fabrics intended for use by the final consumer.

The Main Test Methods

EN 14362-1: Detection and Determination of Certain Listed Aromatic Amines Derived from Azo Colorants

EN 14362-2: Detection and Determination of Certain Listed Aromatic Amines Derived from Azo Colorants

In most cases, Gas Chromatographic Mass Spectrometry (GC-MS) / Thin Layer Chromatography (TLC) Technique are used for result determination.

List of the aromatic amines

	AMINES TESTED	CAS NO.

1.	4-aminodiphenyl/xenylamine/ Biphenyl-4-ylamine	92-67-1
2.	Benzidin	92-87-5
3.	4-chlor-o-toluidine	95-69-2
4.	2-naphthylamine	91-59-8
5.	o-aminoazotoluene/ 4-o-tolylazo-o-toluidine/ 4-amino-2’,3-dimethylazobenzene	97-56-3
6.	2-amino-4-nitrotoluol/5-nitro-o-toluidine	99-55-8
7.	p-chloranilin/4-chloroaniline	106-47-8
8.	2,4-diaminoanisol/ 4-methoxy-m-phenylenediamine	615-05-4
9.	4,4'-diaminodiphenylmethane/ 4,4-methylenedianiline	101-77-9
10.	3,3'-dichlorobenzidine/ 3,3’dichlorobiphenyl-4,4’-ylenediamine	91-94-1
11.	3,3'-dimethoxybenzidine/o-dianisidine	119-90-4
12.	3,3'-dimethybenzidine/4,4’-bi-o-Toluidine	119-93-7
13.	3,3'-dimethyl-4,4'-diaminodipenylmethane/ 4,4’-methylenedi-o-toluidine	838-88-0
14.	p-cresidin/6-methoxy-m-toluidine	120-71-8
15.	4,4'-methylen-bis-(2-chloro-aniline)/ 2,2’-dichloro-4,4’methylene-dianiline	101-14-4
16.	4,4'-oxydianiline	101-80-4
17.	4,4'-thiodianiline	139-65-1
18.	o-toluidine/2-aminotoluene	95-53-4
19.	2,4-toluylendiamin/ 4-methyl-m-phenylenediamine	95-80-7
20.	2,4,5-trimethylaniline	137-17-7
21.	4-aminoazobenzene	60-09-3
22.	o-anisidine/ 2-methoxyaniline	90-04-0
23.	2,4-Xylidin	95-68-1
24.	2,6-Xylidin	87-62-7

Remarks:

Azocolorants that are able to form 4-aminoazobenzene (CAS Nr:60-09-3), generate under the testing condition into aniline and 1,4-phenylenediamine. The detection of it can only be ascertained with the chemical structure of the colorant used.

The 2 ‘Blue Colourants’:

CAS number Index number EC number

Not allocated 611-070-00-2 405-665-4

Component 1: CAS-No.: 118685-33-9; C₃₉H₂₃ClCrN₇O₁₂S.2Na
Component 2: C₄₆H₃₀CrN₁₀O₂₀S₂.3Na

The 2 ‘Blue Colourants’:

A mixture of:

disodium(6-(4-anisidino)-3-sulfonato-2-(3,5-dinitro-2-oxidophenylazo)-1-naphtholato)(1-(5-chloro-2-oxidophenylazo)-2-naphtholato)chromate(1-); and
trisodium bis(6-(4-anisidino)-3-sulfonato-2-(3,5-dinitro-2-oxidophenylazo)-1-naphtholato)chromate(1-)

Definition of Azo Compounds

Azo compounds are compounds bearing the functional group R-N=N-R', in which R and R' can be either aryl or alkyl. The N=N group is called an azo group, although the parent compound, HNNH, is called diimide. The more stable derivatives contain two aryl groups. The name azo comes from azote, an old French name of nitrogen that is derived from the Greek a (not) + zoe (to live).

As Dyes and Pigments

As a consequence of п-delocalization, aryl azo compounds have vivid colours, especially reds, oranges, and yellows. Therefore, they are used as dyes, "azo dyes." Some azo compounds, eg. methyl orange, are used as acid-base indicators due to the different colours of their acid and salt forms. The development of azo dyes was an important step in the development of the chemical industry. Azo pigments are colorless particles (typically earths or clays), which have been colored using an azo compound. Azo pigments are important in a variety of paints including artist's paints. They have excellent coloring properties, again mainly in the yellow to red range, as well as lightfastness. The lightfastness depends not only on the properties of the organic azo compound, but also on the way they have been adsorbed on the pigment carrier. Azo pigments are advantageous because they are non-toxic.

Aryl Azo Compounds

Aryl azo compounds are usually stable, crystalline species. Azobenzene is the prototypical aromatic azo compound. It exists mainly as the trans isomer, but upon photolysis, converts to the cis isomer. Aromatic azo compounds can be synthesized by using an azo coupling reaction, which entails an electrophilic substitution reaction where a aryl diazonium cation attacks another aryl ring, especially those substituted with electron-releasing groups.^[1] Since diazonium salts are often unstable near room temperature, the azo coupling reactions are typically conducted near ice temperatures. The oxidation of hydrazines (R-NH-NH-R') also gives azo compound

Aliphatic Azo Compounds

Aliphatic azo compounds (R and/or R' = aliphatic) are less commonly encountered than the aryl azo compounds. One example is diethyldiazene, EtN=NEt.^[3] At elevated temperatures or upon irradiation, the carbon-nitrogen (C-N) bonds in certain alkyl azo compounds cleave with the loss of nitrogen gas to generate radicals. Owing to this process, some aliphatic azo compounds are utilized as radical initiators. Representative is Azobisisobutylonitrile (AIBN) which is widely used as an initiator in polymerization. Because of their instability, especially for aliphatic ones, care should be taken with the handling of azo compounds or an explosion may occur.