2006 TRI/PRINCETON CONFERENCE 445 the baseline values of all analytical methods. In the case of X-ray fluorescence spectros- copy the values result from silicon on the surface of the hair which is influenced by inorganic silicon from the hair itself. The amount of silicones adsorbed on the hair was determined by ICP-OES analytics preparing extracts from the strands. For this purpose the hair was cut into pieces and the adsorbed silicone was extracted with a mixture of a-xylene and isopropanol. The extracts were analyzed on a Vista MPX Radial (Varian Inc.) ICP device using a certified poly- dimethylsiloxane calibration standard (Conostan®). The concentration of silicon was calculated by taking the mean of the signals at 5 silicon specific wavelengths. The concentrations of silicones were derived from the amounts of silicon by multiplying with a factor (2 .64) derived from pure PDMS. Since for dimethiconol only the terminal methyl groups are substituted by hydroxyl groups, this factor is also valid for this type of silicone. Hair strands were examined without further treatment via X-ray fluorescence spectros- copy by mounting them into a sample holder and analyzing in an Axios-Advanced (Panalytical) spectrometer. A 4kw Rh anode was used for the excitation and a PE002-C crystal for analyzing the wavelength of the fluorescent radiation. The amount of hydro- genated didecene of treated hair strands was determined by extracting the hair with isopropanol. The extracts were derivatized with a mixture of N, O-bis(trimethylsilyl)- trifluoroacetamide (BSTFA) and N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTAFA) to reduce the boiling temperature of the matrix components and increase selectivity. The GC-MS analysis was performed applying hexadecane as internal stan- dard. Due to the structural complexity of didecene, only selected ion traces in a part of the didecene signals were used comparing chromatograms of the pure hydrocarbon and extracts of hair treated with a placebo shampoo without hydrogenated didecene. Wet combing performances were determined using a robotic system combing 10 treated strands per formulation and number of applications. The combing work was determined by integrating the force versus distance curve. The residual combing work was calculated as ratio of (work after shampoo application) / (work before shampoo application) for each strand. The influence of the shampoos to the volume of hair strands was determined applying an imaging system. Images of the hair strand were taken under 5 angles from 0 ° to 180 ° calculating the volume from the 5 derived projections. Relative volumes were calculated as ratio of volume after versus before shampoo application for each strand. RES UL TS AND DISCUSSION DETERMINATION OF THE AMOUNTS OF SILICONE ADSORBED TO THE HAIR FROM SHAMPOO APPLICATION Figure 1 shows the amounts of silicone found on hair strands after repeated application of a commercial 2-in-l shampoo from the European market determined from ICP-OES analysis. It can be seen that already after a single treatment with the shampoo a huge amount of dimethiconol was found adsorbed to the hair. There is no variation within the margin

446 JOURNAL OF COSMETIC SCIENCE 700 Washing with SLES 600 500 · a, 400 � 300 200 100 0 0 3 5 5+SLES 5+2SLES 5+3SLES Number of treatments Figure l. Amount of silicone deposited at hair strands repeatedly washed with a 2-in-1 shampoo and determined by ICP-OES. of error of the method after 3 and 5 times treatment. By checking the removability with SLES it can be seen that even after 3 times washing with the surfactant about 50% of the silicone remains on the hair. In Figure 2 the amounts of silicone detected on hair strands treated with 2 shampoos of the same brand and type, from the European and the Asian markets are given, respec- tively. These data were also derived by ICP-OES. As the Asian shampoo contains more than 3.5 times more dimethicone than the Euro- pean version, the different amounts of silicone found adsorbed to the hair can be easily understood. For both shampoos there seems to be a build-up effect after repeated treatment. In contrast to the example given in Figure 1, the silicone was removed to a higher extent. Hair strands treated in the same way but analyzed with X-ray fluorescence spectroscopy gave the XRF signals depicted in Figure 3. Since there is a background signal resulting from (inorganic) silicon in the hair, and the effect of the hair matrix to the XRF signal is unknown, this method currently delivers relative data only. For the Asian shampoo, the results from ICP-OES analytics were confirmed. On the other hand, the signals resulting from the small amounts of dimethicone adsorbed on the hair from the Euro- pean shampoo are in the range of the background signal for untreated hair and thus below the limit of detection. DETERMINATION OF THE AMOUNTS OF HYDROGENATED DIDECENE ADSORBED ON THE HAIR FROM SHAMPOO APPLICATION In contrast to silicones, for emollients without chemical elements allowing the appli- cation of specific detection methods, chromatographic methods have to be developed.