182 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table IV. The most important types of oxidative hair colour intermediates Substituents No. of Position Base isomers Abbreviation commonly used Diamino 3 ortho meta para Dihydroxy 3 ortho meta para Trihydroxy 3 1.2.3 1.2.4 1.3.5 Hydroxy 3 2. amino 3. 4. Methyl 6 2.3 diamino 2.4 2.5 2.6 3.4 3.5 Hydroxy 6 2.3 diamino 2.4 2.5 2.6 3.4 3.5 Diamino 6 2.3 methyl 2.4 ether 2.5 2.6 3.4 3.5 Nitro 6 3 nitro diamine 4 nitro 2 nitro 4 nitro 5 nitro 2 nitro Hydroxy 2 tt Diamino 6 2.3 2.4 2.5 2.6 3.4-3.5 phenylenediamine phenylenediamine phenylenediamine dihydroxybenzene = pyrocatechol dihydroxybenzene = resorcinol dihydroxybenzene = hydroquinone trihydroxybenzene = pyrogallol trihydroxybenzene = hydroxyhydroquinone trihydroxybenzene = phloroglucine aminophenol aminophenol aminophenol toluylenediamine toluylenediamine toluylenediamine toluylenediamine toluylenediamine toluylenediamine diaminophenol diaminophenol-- arnidol base diaminophenol diaminophenol diaminophenol diaminophenol diaminoanisole diaminoanisole diaminoanisole diaminoanisole diaminoanisole diaminoanisole 1.2.phenylenediamine 1.2.phenylenediamine 1.3.phenylenediamine 1.3.phenylenediamine 1.3.phenylenediamine 1.4.phenylenediamine naphthol naphthol diaminopyridine diaminopyridine diaminopyridine diaminopyridine diaminopyridine OFD MFD PFD PCT RES HCH PGL PHL 2AF 3AF 4AF 24TDA 25TDA 24DAF 24DAA 4NOFD 2NPFD AN BN 26DAP

RISK-BEARING SUBSTANCES IN COSMETICS 183 Table V. List of reference compounds: oxidative hair colour intermediates OFD o. Phenylenediamine 2AF 2.aminophenol PCT pyrocatechol MFD m. Phenylenediamine 3AF 3.aminophenol RES resorcinol PFD p.Phenylenediamine 4AF 4.aminophenol HCH hydroquinone 24TDA 2.4.tolylenediamine M4AF 4.methylaminophenol PHL phloroglucine 25TDA 2.5.tolylenediamine (metol base) PGL pyrogallol 24DAF 2.4.diaminophenol 2NPFD 2.nitro.p.phenylene- AN naphthol ct (amidol base) diamine BN naphthol I• 24DAA 2.4.diaminoanisole 4NOFD 4.nitro.o.phenylene- CRES chlororesorcinol 26DAP 2.6.diaminopyridine diamine 2CPFD 2.chloro.p.phenylene- diamine There is one important factor that is worth mentioning. The silica support must be carefully considered to obtain good resolution and good shapes of the spots. We did not have satisfaction with several kinds of precoated supports, including self-coated silica with gypsum binder. The purest kind of silica (without binder) (for instance Silica HR, Merck) gave the best results. Colouring of the iodine vapour of the spots on these self-made plates will also give much more beautiful colours (in particular the starting colours), which aids the identification procedure. Precoated plates will only give brownish colours with iodine vapour for all the components. Procedure. The solvent for extract or reference solutions is always methanol: ethylacetate = 1:4 vol. Extracts and reference solutions should always be preserved with several crystals of sodium-metabisulphite. Reference solutions: Make 0.1• standard solutions of the substances of Table V in the above solvent mixture. Standard mixture: A mixture of 0.1 • each of PFD, 2AF, 3AF, 4AF, RES, AN. Extraction: Mix I g of the product and 4 ml of the solvent. Heat a little on a waterbath. Add ca 250 mg sodium-metabisulphite and ca 500 mg sodium-sulphate exsicc. Shake the mixture vigorously. Use the clear liquid for tic. This extract can only be kept for ONE day. Optimal spotting is very important. For 20 x 20 cm plates 5 pg is the optimal amount for these tic plates (except for 2NPFD •- pg for 3AF.4NOFD.HCH. AN.BN. 10 lag, and PGL 15 I-tg). For small plates (10 cm) half of these amounts. Mixed spots of extracts and reference solutions can be used for confirmation. Preliminary tlc. The purpose of preliminary tlc on precoated tlc plates (10 cm) is the estimation of the concentration level in the product, in order to permit optimal spotting in the main identification procedure. It is made with the following spots of the extracts: 1-2-5-20 I-tl of the extract and a reference mixture spot of 2 lag of 25TDA-3AF-RES. Solvent same as in