234 JOURNAL OF COSMETIC SCIENCE L-ascorbic acid sodium salt (NaAsc) as an antioxidant agent were added to a 560-ml sodium teraborate solution. The solvents were mixtures of MeOH and Soerensen buffer, pH 8 in various proportions. Mobile phase (aqueous phase B): a 0.05 M acetic acid solution was adjusted to a pH of 5.9 with a 10% ammonia solution and filtered through a 0.45-l•m filter. When not in use, the eluent was stored at a temperature of 4øC to prevent microbiological growth. Samples. The matrix products and the dye intermediates used in the experiments are given in Tables I and II, respectively. All dye intermediates and matrix component concentrations were selected according to COLIPA data. Stock solutions of dye intermediates at a concentration of 0.1 g/100 g were prepared in mixtures of various proportions of MeOH and Soerensen buffer (containing NaAsc as an antioxidant agent), ranging from 40% to 90% Soerensen buffer. Sample solutions of dye intermediates at a concentration of 0.025 g/100 g were prepared by dilution from the stock solutions in mixtures of Soerensen buffer and MeOH ranging from 30% to 60% Soerensen buffer. Stock solutions of matrix components were prepared in MeOH- or isopropanol- Soerensen buffer mixtures of different proportions. Sample solutions of the matrix com- ponents at various concentrations (Table I) were prepared by dilution from the stock solutions in MeOH- or isopropanol-Soerensen buffer mixtures (abbreviations are given in the Chemicals section). Table I Selected Matrix Compounds, Functions, Concentrations, and MeOH Proportions Used Concentration Compound Function (g/100 g) MeOH proportion (%) Oleic acid (OA) Oranex HT © (ORA) TEA-dodecylbenzenesulfonate (TDS) Cetrimonium chloride (CC) Lauric diethanolamide (LDA) BHT Syntopon 8 D1 © (EOP) Nonoxynol- 12 (NOL) n-Nonylamine 98% (NNO) Sodium lauryl sulfate (LS) Polyquaternium-11 (PQ) Methylparaben (MP) Polyvinylpyrrolidon (PVP) Sodium sulfite (SS) Triethanolamine (TEA) DEDM-Hydantoin (DEDM) Dimethicone copolyol (DC) L-ascorbic acid sodium salt (NaAsc) Surfactant, cleansing agent 5 100 Unknown 3 100 Surfactant, deansing agent 0.5 90 Surfactant, emulsifying agent 0.5 Surfactant, deansing agent 2 Antioxidant 0.25 Perfume solubilizer 6 Surfactant, emulsifying agent 3 Unknown 25 Surfactant, cleansing agent, denaturant 3 Antistatic agent, film former, hair fixative 2 Preservative 0.05 Antistatic agent, film former, hair fixative 2 Antioxidant, reducing agent 2 pH adjuster 1.5 Preservative 0.05 Emollient, hair conditioning agent 2.5 Antioxidant, pH adjuster ** 90 75 70 70 70 60 60 60 60 60 40 40 0 * DC was prepared in an isopropanol-Soerensen buffer mixture with 67% isopropanol. ** The Soerensen buffer contains NaAsc 2 g/l.

MATRIX COMPOUNDS AND OXIDATIVE HAIR DYES 235 Table II Retention Times for Forty-Seven Dye Intermediates, Each of Which Was Measured as a Single Component Solution (n = 3) Retention time (rain) Dye Mean RSD (%) 3,4-Diaminobenzoic acid 2.75 1.54 2,4-Diaminophenol 3.95 0.17 2,4-Diaminophenol HC1 3.98 0.18 p-Phenylenediamine sulfate 5.21 0.54 P hloroglucinol 5.23 12.56 p-Phenylenediamine 5.60 9.34 Pyrogallol 5.90 3.59 2-Amino-3-hydroxypyridine 5.91 0.84 Hydroquinone 6.02 6.92 p-Aminophenol 6.13 3.46 m-Phenylenediamine sulfate 7.00 3.23 m-Phenylenediamine 7.15 6.42 2,6-Diaminopyridine 7.91 3.93 m-Aminophenol 8.04 3.43 Toluene-2,5-diamine sulfate 8.50 7.73 Resorcinol 9.23 4.67 4-Amino-m-cresol 9.70 1.82 0-Phenylenediamine 9.86 3.87 2-Methoxy-p-phenylenediamine sulfate 9.94 1.35 0-Aminophenol 10.51 5.98 Pyrocatechol 11.23 18.06 p-Methylaminophenol sulfate 11.88 2.02 2-Methylresorcinol 11.89 6.84 2-Chloro-p-phenylenediamine sulfate 12.33 2.01 Toluene-2,4-diamine 12.78 8.85 2-Nitro-p-p henylenediamine 13.14 2.20 4-Nitro-0-phenylenediamine 15.10 2.53 2-Amino-4-nitrophenol 15.50 3.01 5-Amino-o-cresol 15.66 4.11 Toluene-3,4-diamine 17.53 7.50 6-Amino-m-cresol 17.95 1.34 2-Amino-p-cresol 18.07 2.90 p-Anisidine 18.47 4.21 2-Amino- 5 -nitrophenol 18.66 3.14 4-Chlororesorcinol 20.44 3.70 4,4'-Diaminodiphenylamine sulfate 20.83 0.75 1,6-Naphtalenediol 25.23 2.24 2,7-Naphtalenediol 25.81 1.59 3-Methyl- 1-phenyl-2-pyrazoline-5-one 26.01 6.39 4-Chloroaniline 26.82 2.50 2,3-Naphtalenediol 27.88 2.38 N- Phenyl-p-phenylenediamine 29.56 3.64 2-Naphtol 29.71 0.93 N, N-Diethyl-m-aminophenol 30.00 0.02 1-Naphtol 30.01 0.42 3 -tert-butyl-4- hydroxyanisole 31.85 0.58 4-Hexylresorcinol 32.26 0.55