j. Cosmet. Sci., 54, 527-535 (November/December 2003) Evaluation of hair fiber hydration by differential scannino calorimetry, oas chromatooraphy, and sensory analysis KLt•ZIA M. S. BELLETTI, ISRAEL H. FEFERMAN, TfkNIA R. O. MENDES, ANGELA D. PIACESKI, VAL•RIA F. MONTEIRO, NEFTALI L. V. CARRE'O, ANTONINHO VALENTINI, EDSON R. LEITE, and ELSON LONGO, 0 BotiMrio, Av. Rui Barbosa 3450, Afonso Pena, Sa•o Josg dos Pinhals, PR, Brazil 83065-260 (K.M.S.B., I.H.F., T.R.O.M., A.D.P.), CMDMC/LIEC/DQ/UFSCar, Universidade Federal de Sago Carlos, Rod Washington Luis, Km 235, Caixa Postal 676, Sa7o Carlos, SP, Brazil 13565-905 (V.F.M., N.L.V.C., E.R.L., E.L.), and Departamento de Quoemica, UFSC, CP-476, CEP 88040-900, Florian•polis, SC, Brazil (A.V.). Accepted for publication March 19, 2003. Synopsis Hair hydration is one of the effects that consumers most expect when using a cosmetic hair product. The purpose of this study was to combine differential scanning calorimetry (DSC) and gas chromatography (GC) techniques for a precise evaluation of the water content in hair fiber. DSC allowed determination of the bonding strength of water to hair fibers by quantifying the amount of energy required to remove the water. The amount of water thus removed was determined by GC. Post-treatment sensory evaluations of hair tresses were conducted to determine whether the values obtained with these techniques correspond to the mois- turizing sensation perceived by consumers. INTRODUCTION Moisture content in hair can be detected and quantified by a variety of techniques that include gravimetry (1-3), electric measurements (4,5), and evaporimetry (6). Microscopy, one of the techniques of reference for evaluating hydration, was used to determine changes in fiber diameter, surface, and volume (7,8). Hair hydration was determined by near infrared spectroscopy (NIR) combined with sensory evaluation (9). Measurements of hair fiber tension-stretch values were used for indirect evaluation of hair hydration (10). Differential scanning calorimetry (DSC) techniques have been applied by Cao (11) to study thermal behavior of hair. Wortmann et al. (12) have used DSC to determine keratin denaturation in bleached hair fibers. Since this technique quantifies the thermal 527

528 JOURNAL OF COSMETIC SCIENCE energy that must be transferred to a material to induce physical changes, it allows measuring the heat of vaporization, melting, and phase transition of different materials. In his studies, Cao (11) identified two characteristic temperature ranges: one, from 0øC to 200øC, for water present in hair, and the other, from 250øC to 280øC, for the crystalline phase transition of tx-keratin. Gas chromatography (GC) techniques using a mass spectrometry detector (GS/MS) have been applied for forensic purposes to detect traces of drugs in hair fibers (13,14). When heated, hair releases a vapor whose components can be identified and quantified by injecting the vapor into a gas chromatograph. The thermal conductivity detector asso- ciated with the GC technique is appropriate and sufficiently sensitive for the detection and quantification of water and carbon dioxide in gas mixtures (15). The objective of this study was threefold: to apply DSC techniques to evaluate the intensity of the bonding energy of water to hair to apply GC techniques to quantify the amount of water present in hair fibers as a result of a variety of cosmetic treatments and to determine whether the resulting values correspond to the moisturizing sensation perceived by consumers. MATERIALS AND METHODS Two treatments (1 and 2) were evaluated with leave-on products recommended for damaged hair, and two treatments (3 and 4) were evaluated with rinse-off products recommended for normal hair. Standard Caucasian medium-brown hair tresses (De Meo Brothers), measuring 30 cm in length and weighing approximately 2.0 g each, were prepared for this study. For the treatments recommended for damaged hair, the tresses were bleached for 30 minutes in a solution containing hydrogen peroxide (20 vol.), reagent grade ammonium hydroxide, and reagent grade ammonium persulfate in the ratio of 2:1:0.5, respectively. Each tress was previously washed with 10% lauryl ether sodium sulfate to remove impurities. All tresses were wetted under a constant flow of distilled water (10 ml/s) for 15 seconds and treated with 200 pl of each product the products were applied along the length of the tresses and massaged over the fibers for 15 seconds. Except for those treated with leave-on products, the tresses were rinsed under a constant flow of distilled water (10 ml/s) for 15 seconds and then dried with a professional hairdryer at room temperature (24øC + 1). This entire procedure represented one wash. Five washes were carried out for each treatment (Table I). The control tress was treated in the same way as all the others, except for the application of the moisturizing products. Table I Hair Tress Treatments Treatment Product Tress condition 1 A (Not rinsed) Damaged 2 B (Not rinsed) Damaged 3 C (Rinsed) Undamaged 4 D (Rinsed) Undamaged