STABILITY OF PEDIATRIC SUNSCREEN EMULSION 375 Calculation of the solar protection factor. In order to determine the effectiveness of the formula- tion in terms of SPF, ten volunteers were chosen to take part in the study. The source of radiation was set to a constant spectral emission within the UV region, and appropriately fi ltered to avoid cutaneous harm, in accordance with COLIPA recommendations for the spectral quality of UV radiation (20). The device used was a solar malingerer Multiport®, with an emission spectrum ranging between 290 and 400 nm. Given the variability of the skin’s reactivity to UV radiation, randomly selected areas of the back of each volunteer were treated with one impregnated towel prior to radiation exposure. The MED evaluation of protected skin (MEDp) and unprotected skin (MEDn) was carried out visually and simultaneously under a perfect standard source of diurnal light: MED • p was considered as the quantity of radiant energy required to cause non-ambiguous redness, with defi ned edges, equivalent to that required for the MEDn area, evaluated by visual comparison after 16 or 24 hours of exposure. MED • n was considered as the quantity of radiant energy required to produce the minor visual redness obtained through MEDp under a perfect standard source of diurnal light. Impregnated towelette preparation. The volume of formulation required for the impregnation of the towelettes was determined after a series of trials and from the experience gained from the validation of different formulations in previous studies. The total volume of formulation was therefore calculated according to the dimensions, weight, and total number of towels used in this trial. The dimensions of the towels used in this study were 200 × 175 mm, and the quantity of formulation required was calculated according to the following parameters: (a) VOL (sunscreen emulsion volume necessary to impregnate the towel) (b) G (non-woven weight) (c) D (towel dimensions, width and length) (d) C.I. (coeffi cient of impregnation as stipulated by COLIPA (21), for the purpose of obtaining a homogeneously moistened surface for correct application. This coeffi cient is experimentally calculated and is dependent on the viscosity of the fl uid) (e) N (number of towels contained in the package to be impregnated) Organoleptic characteristics. Organoleptic characteristics were classifi ed according to the fol- lowing terminology: thick, hard, creamy, smooth, soft, dry, thin, spreadable, cool, and warm (22). The sunscreen emulsion and the towel were subjected to the sensory analyses of color, odor, texture, consistency, and external appearance (exudate), at 0 h, just after preparation, and 24 h after preparation. The same analyses were carried out after storage at all selected temperatures and time intervals, with determinations for both samples (T and E) performed in triplicate. Dry matter. A thermobalance, Sartorius model 150C-000230V1 MA, was used at a tem- perature of 105°C to determine the quantity of water present in both emulsion and towel formulations, in order to assess chemical stability. Density. Density was determined at 20°C with a 100-ml graduated glass cylinder and a METAS hydrometer with a nominal range of between 0.900 and 1.000 and a minimal division of 0.002 g/m3.

JOURNAL OF COSMETIC SCIENCE 376 pH. In order to detect any possible variations in pH, values were measured in both formu- lations using an mv/pH meter, Crison model digit 501, at the determined intervals throughout the entire storage period. Microbiological control. An impregnated towel was introduced into an inactivator medium of preservatives (MIP) in a laminar fl ow cabinet (Testalr model BIO IIA). After incuba- tion for 30 minutes, 1 ml of MIP was planted onto both a Triptona soy agar (TSA) me- dium plate, for the detection of aerobic bacteria, and a Sabouraud’s medium plate, for the detection of fungi and yeasts. The plates were incubated at 37°C for 48 hours and at 22°C for fi ve days, respectively (23). A negative control was performed by planting 1 ml of sterile peptone water and 1 ml of inactivation medium (MIP) in each of the culture me- dia. In the case of the samples from the emulsion, the same technique was carried out by adding the emulsion to the inactivation medium (MIP). Rheological characteristics. The rheological properties of the formulations were studied in terms of viscosity, a parameter closely related to stability (24). Assays were run at increas- ing shear rates in a Brookfi eld DV II+ viscosimeter (Brookfi eld Engineering Laboratories, Stoughton, MA). Stability. To determine the effect of temperature on the stability of the samples, tests were carried out at 4° and 25°C. The formulae were also tested in a closed container, intro- duced into a Friocell 111 oven at 40°C throughout the entire test period. The samples were then subjected to a centrifugal testing using a microcentrifuge (Kendro, Heraeus, model peak 17, at 3.500 rpm) for ten minutes, to ascertain whether any separation of the two phases of the emulsion had taken place. RESULTS AND DISCUSSION The results are expressed as the mean and standard deviation of three determinations of samples from each formulation, at each temperature and storage time interval. All the results were compared using variance analysis (ANOVA) for a 95% confi dence level to detect any signifi cant differences. Triplicate analysis commenced at time 0 and continued at each time interval until fi naliza- tion of the storage period, a procedure that indicates whether any modifi cation of the formu- lae occurs over time and at determined temperatures. The results are presented in Table II. CALCULATION OF SOLAR PROTECTION FACTOR (SPF) Final SPF was determined from the average of the values for individual SPF (SPFi) for the ten volunteers (n) included in this study. The individual value of the SPF of the emulsion was defi ned as the ratio of the MEDp and MEDn on the same volunteer: i SPF = n ¦SPF The results obtained from the analysis of the emulsion proposed in this work reached an SPF of 30, classifi ed as a high protection value according to guidelines published in 2006 (2006/647/EC) (25).