MATRIX COMPOUNDS AND OXIDATIVE HAIR DYES 233 column temperature was kept constant by means of the thermostat of an electrochemical detector (Decade, Antec Leyden, Leiden, The Netherlands). Data processing was done with the Data System 450-MT2/DAD series (Kontron Instruments S.P.A.). The column was a Merck Lichrospher RP 60 Select B, 250 x 4 mm, 5-1am particle size. In some cases, a UV-Vis spectrophotometer (Lambda 7 from Perkin Elmer) was used additionally with the above equipment. CHEMICALS L-Ascorbic acid sodium salt (NaAsc), 3,4-diaminobenzoic acid (3,4-daba), p- aminophenol (4-ap), m-aminophenol (3-ap), 0-aminophenol (2-ap), 2,4-diaminophenol (2,4-dap), 2,4-diaminophenol HC1 (2,4-daph), 4-amino-m-cresol (4-a-3-mp), 2-amino- p-cresol (2-a-4-mp), 6-amino-m-cresol (2-a-5-mp), 5-amino-0-cresol (4-a-2-ht), 2-amino-5-nitrophenol (2-a-5-np), 2-amino-4-nitrophenol (2-a-4-np), N,N-diethyl-m- aminophenol (3-deap), p-phenylenediamine (1,4-pd), m-phenylenediamine (1,3-pd), 0- phenylenediamine (1,2-pd), 2-nitro-p-phenylenediamine (2-n-l,4-pd), 4-nitro-0- phenylenediamine (4-n-l,2-pd), 2-chloro-p-phenylenediamine sulfate (2-cl-l,4-pds), N- phenyl-p-phenylenediamine (4-adp), 4,4'-diaminodiphenylamine sulfate (4,4'-dadps), resorcinol (res), 4-chlororesorcinol (chlres), 4-hexylresorcinol (hres), p-anisidine (1,4-ad), 2,6-diaminopyridine (2,6-dap), 2-amino-3-hydroxypyridine (2-a-3-hp), 2-methylresor- cinol (2,6-dht), toluene-2,4-diamine (2,4-dat), toluene-3,4-diamine (3,4-dat), toluene- 2,5-diamine sulfate (2,5-dats), 1-naphtol (1-nap), 2-naphtol (2-nap), 1,6-naphtalenediol (1,6-dhnap), 2,3-naphtalenediol (2,3-dhnap), 2,7-naphtalenediol (2,7-dhnap), phloro- glucinol (phlg), pyrogallol (pg), hydroquinone (hq), pyrocatechol (pc), p- methylaminophenol sulfate (met), 2-methoxy-p-phenylenediamine sulfate (2,5-das), 3-tert-butyl-p-hydroxyanisole (3-tb-4-ha), 4-chloroaniline (4-cla), 3-methyl-l-phenyl-2- pyrazoline-5-one (3-m-l-p-2-p-5-o) were obtained from Fluka. p-Phenylenediamine sul- fate (1,4-pds), and m-phenylenediamine sulfate (1,3-pds) were kindly provided by "Les Colorants Wackherr," Saint-Ouen l'Aum6ne, France. Sodium tetraborate decahydrate (p.a.), acetic acid 95% (suprapure), ammonia 25% (suprapure), hydrochloric acid (0.1 M), oleic acid (OA) (p.a.), n-heptane (p.a.), isopropanol (p.a.), sodium sulfite (p.a.) (SS), and polyvinylpyrrolidon (PVP) were obtained from Merck. BHT (butylated hydroxy- toluene), methylparaben (MP), and lauryl sulfate (LS) were obtained from Sigma. Lauric diethanolamide (LDA), TEA-dodecylbenzenesulfonate (TDS), and Syntopon 8 D1 © (ethoxylated octyl phenol-EOP) were provided by Witco S.A. Triethanolamine (TEA) was obtained from Mobi-Lab bvba, Zutendaal, Belgium. DEDM-hydantoin (DMDM), dimethicone copolyol (DC), nonoxynol-12 (NOL), and polyquaternium-11 (PQ) were kindly provided by "Keuringsdienst van Waren," Enschede, The Netherlands. n- Nonylamine 98% (NNO) was obtained from Janssen Chimica, and Oranex HT © (ORA) was provided by Spinnrad GmbH, Gelsenkirchen, Germany. Cetrimonium chloride (CC) and methanol (HPLC quality) were obtained from Fluka. Pure water (18.2 Ml•/cm quality) used for the preparation of solutions was obtained from a MilliQ Plus 185 system (Millipore, Molsheim, France). PREPARATION OF REAGENTS Solvents and chromatographic mobile phase Buffer solution pH 8 (Soerensen buffer): 440 ml hydrochloric acid (0.1 N) and 2 g/1

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.