DMAE AND DMAE BITARTRATE IN COSMETICS 273 Nuclear magnetic resonance. The 1 H-NMR spectra were recorded with Varian Direct drive (400 MHz) spectrometers for solutions in D2O. RESULTS AND DISCUSSION DIFFERENTIAL SCANNING CALORIMETRY Figure 2 shows the thermogram of DMAE bitartrate at room temperature. Two endother- mal peaks were evident: one at 67.1°C and a larger peak at 113.6°C that marked the melt- ing point (melting range: 112.7°–118.2°C). The heat exchanges for these peaks were 55 J/g and 114 J/g. The basal heat curve showed signs of shift between 200°C and 212°C. Stability was evaluated by comparing the DSC thermograms obtained at room tempera- ture with those recorded at 40°C and 60°C. Figure 3 shows the results for DMAE bitar- trate at each temperature. The endothermal peak at 67.1°C was no longer evident, although large peaks were seen at 114.5°C (40°C) and 115.1°C (60°C). Disappearance of the smaller endothermal peak may indicate loss of occluded water due to crystallization as a result of evaporation after storage of the samples at a the two higher temperatures. Figures 4 and 5 compare the stability of DMAE bitartrate at different times in samples kept at room temperature versus 40°C or 60°C. The behavior at days 7, 14, and 30 was similar to that of the room-temperature samples, and the endothermal peak remained unchanged. Calorimetric tests thus detected no changes in any of the samples kept at 25°C, 40°C, or 60°C for different periods. All curves showed the characteristic melting point for DMAE bitartrate. ULTRAVIOLET SPECTROSCOPY The spectra showed no clear peaks for maximal absorbance, and so the UV spectros- copy results were uninformative for the purposes of characterizing DMAE and DMAE bitartrate. Figure 7. FTIR spectra of DMAE bitartrate.

JOURNAL OF COSMETIC SCIENCE 274 Figure 8. 1 HNMR spectra of DMAE at 25°C (A), 40°C (B), and 60°C (C). INFRARED SPECTROSCOPY We used IR spectroscopy to look for possible structural changes in DMAE and DMAE bitartrate after storage at different temperatures. Figures 6 and 7 show the positions of