DETERMINATION OF BAC IN WET WIPES 5 Applied voltage is separation power of CE beside other parameters. For this purpose, dif- ferent separation potentials between 5 and 20 kV were investigated to analyze BAC. When the obtained results were evaluated, it was seen that peak areas decreased with increasing separation potential. But at the same time, peak shapes changed and there was no separa- tion at high potential levels. When the potential decreased, although relatively good peak area values were obtained, peaks were not symmetrical and well shaped. It was nec- essary that an optimum separation voltage should be selected to see the regular and sym- metrical shape of peaks and obtain higher peak area values. According to the results, 10 kV separation potential was selected to analyze BAC. At the end of the preliminary studies, optimum electrophoretic conditions were deter- mined as follows—the BGE: 75 mM (pH 6) phosphate buffer mixed with ACN at a ratio of 70:30 temperature: 18°C injection condition: 50 mbar pressure for 3 s separation poten- tial: 10 kV. A typical electrophoregram of BAC at these optimized conditions is presented in Figure 2. We surmise that the fi rst peak belongs to the C10 derivative of BAC and the second one belongs to the C12 derivative of BAC because we assume that, of the two mol- ecules only differing by two CH2 groups, the molecule with the larger molecular mass has the lower electrophoretic mobility. METHOD VALIDATION Validation of the method was made according to USP (United States Pharmacopeia) guidelines for this study. SYSTEM SUITABILITY System suitability test was applied for the developed method. According to the literature, system suitability test should contain some parameters like capacity factor, resolution, etc. For this purpose, a standard solution of BAC at a medium concentration was injected to the CE system for six times. Results of the system suitability test for this study is Figure 2. Electrophoregram of standard BAC solution in 75 mM (pH 6) phosphate buffer mixed with ACN at a ratio of 70:30 at 18°C injection condition = 50 mbar pressure for 3 s separation potential = 10 kV. Detection by absorbance at 214 nm.

JOURNAL OF COSMETIC SCIENCE 6 presented in Table I. According to these results, the system of the developed method was appropriate to analyze BAC species. SELECTIVITY Selectivity of the developed method was investigated by comparing standard solution of BAC, wetting solution obtained by wrinkling of the wet wipe samples, and wetting solu- tion without BAC. All electrophoregrams showed that BAC peaks were observed clearly in all electrophoregrams and there was no interference. LINEARITY AND CALIBRATION When the preexperiments were carried on, a trend was observed that peak areas of both peaks were increased linearly with concentration. When the calibration curves were con- structed between 0.003 and 0.25 mg/ml of BAC, it was seen that the curve was linear according to the correlation coeffi cients (0.999 and 0.989 for C10 and C12 derivatives, respectively). However, linearity of the method developed should be controlled and for this purpose, a Mandel test was used. Mandel test evaluates the change of the data sets by comparing constructed linear graph with polynomial graph statistically and at the end of the calculations, F values are compared with theoretical F values. If the calculated F value is lower than theoretical F value, the change of signal versus concentration is linear. For studied data set, theoretical F value was 5.59 at 95% confi dence interval. Calculated Table I System Suitability Test Results (n = 6) Parameter C10 derivative C12 derivative Capacity factor (k') 2.700 2.837 Resolution (R) 1.605 1.605 Number of theoretical plates (N) 34,803.54 37,240.78 Tailing factor (T) 1.100 1.050 Relative standard deviation (RSD) 0.56 0.46 Table II Calibration Curve Parameters for the CE Method Developed to Determine BAC Parameter C10 derivative C12 derivative Dynamic range (μg/ml) 1.96–165.50 0.98–82.00 Slope 1.216 1.231 Intercept 2.779 1.986 Ftheorethical (95% CI) 5.59 5.59 Fcalculated -0.98 0.01 LOD (μg/ml) 0.313 0.309 LOQ (μg/ml) 1.042 1.029 R2 0.999 0.989 CI: confi dence interval.