DMAE AND DMAE BITARTRATE IN COSMETICS 271 Spain), dimethylaminoethanol bitartrate, supplied as a white powder by Roig Farma-Grupo (Fagron), and deionized distilled water, supplied by Interapothek (Murcia, Spain). METHODS Three sets of samples were prepared. One set was stored at room temperature (20°–25°C), one at 40°C, and the third at 60°C. During the 30-day study period the molecular stabil- ity of the active principle was measured after the fi rst 24 h and at seven-day intervals thereafter in samples kept at all three temperatures. The stability of free-base DMAE and DMAE bitartrate during a 30-day period was also studied in aqueous solutions at room temperature. Figure 3. DSC thermograms of DMAE bitartrate at 40°C and 60°C. Figure 4. DSC thermograms of DMAE bitartrate during storage at 40°C (stability at different times).
JOURNAL OF COSMETIC SCIENCE 272 Measurements were made in triplicate for each formula at each sampling time and storage temperature. The results are reported here as the mean of the three values ± standard deviation. All results were compared by analysis of variance (ANOVA) to identify sig- nifi cant differences. Differential scanning calorimetry. The DSC thermograms of DMAE bitartrate were recorded with a Mettler FP80 differential scanning calorimeter, from 50°C to 300°C, at a rate of 5°C/min. Test samples weighing 5–6 mg were analyzed in crimped aluminium sample pans. Ultraviolet spectroscopy. Ultraviolet spectra were recorded with a Perkin Elmer UV/Vis spectrometer. A precisely weighed amount of the active principle was dissolved as appro- priate, and scans were obtained at wavelengths of 200–300 nm. Infrared spectroscopy. Infrared spectra were recorded with a Perkin Elmer FT-IR Spectrum One instrument. Solid samples were analyzed with potassium bromide, and liquid sam- ples were analyzed with sodium chloride disks. Figure 5. DSC thermograms of DMAE bitartrate during storage at 60°C (stability at different times). Figure 6. FTIR spectra of DMAE.
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