503 INFLUENCE OF MENSTRUAL CYCLE (Equation 1). This transformation normalizes X i spectrum by calculating the area under the curve Σx ij and makes the area under the curve the same for all spectra (24). New X X x i i j ij = ∑ (1) RESULTS AND DISCUSSION The basic principle of mass spectrometry is to generate ions from organic and inorganic compounds through an appropriate ionization method, to separate them through their m/z ratio in a mass analyzer, and to identify and/or quantify the compounds from the m/z ratio of the ions using a detector that “counts” them and transforms the signal into an electric current. The magnitude of the electrical signal as a function of the m/z ratio is converted by a data processor, which generates the corresponding mass spectrum (21). Headspace consists of the gaseous atmosphere surrounding a sample. The technique involves the collection of compounds from this atmosphere statically or dynamically to an adsorbent device. When using an adsorbent, the collected material must be released (extracted) with a solvent or temperature (25). It allows us to map the performance of an aromatic composition applied on the skin and identify degrading products during experimental times (18). The headspace technique applied was semiquantitative because the peaks found in the chromatograms resulted from the suction generated by the vacuum pump, thus causing Figure 1. Surface contour plot from the volatile components of Ciclo® 1910 emitted by volunteer 19 during menstrual cycle follicular phase after GC/MS analysis. Figure 1 corresponds to the mass spectra data, specifically to the abundance data of the different m/z fragments in the abscissa axis (x) as a function of the retention time in the coordinate axis (scan-y).

504 JOURNAL OF COSMETIC SCIENCE interferences (example: body odor and experimental variation during collection). The true quantitative composition is obtained by the direct injection of the aromatic preparation in the chromatograph. The interferences are most prevalent for the bottom notes of the fragrance, which can be easily hydrolyzed by sweat. Additionally, their release from the skin may not be efficient due to their higher molecular weight and lower volatility. Therefore, the analysis depends on the fragrance-substrate interaction (17,18). Studies show that other factors, such as pH, skin type (dry or oily), gender, and race affect the evaporation of perfumes applied on skin (26). Figure 2. Chromatogram of volatile components of skin’s composition for volunteer nb.1. (A) initial experimental time, (B) after 3 h, and (C) after 6 h. The black chromatogram corresponds to the follicular phase the blue chromatogram corresponds to the luteal phase the red chromatogram corresponds to the menstrual phase and the green chromatogram corresponds to the ovulatory phase.