j. Soc. Cosmet. Chem., 46, 329-342 (November/December 1995) Analysis of cosmetic ingredients by continuous-flow fast atom bombardment liquid chromatography-mass spectrornetry SEIICHI YOSHIDA, RYUJIRO NAMBA, TASUKU TAKAMATSU, and MASAHIRO MATSUOKA, Analytical Research Group, Safety & Analytical Research Center, Shiseido Research Center, 1050 Nippa-cho, Kohoku-ku, Yokohama, Japan 223 (S. Y., T.T., M.M. ), and Analytical Research Division, Pharmaceutical Research Laboratories, Shiseido Research Center, 2-12-1 Fukuura, Kanazawa-ku, Yokohama, Japan 236 (R.N.). Received September 27, 1994. Synopsis In order to study the applicability of continuous-flow fast atom bombardment mass spectrometry (CF-FAB MS) combined with reversed-phase high-performance liquid chromatography (HPLC) using a methanol- and-water mixture as a carrier for cosmetic analysis, 30 compounds frequently used in cosmetics were studied by CF-FAB MS to establish their detection limits. Instrumental optimization was carried out for post-column addition of a matrix solution to adjust the methanol concentration at the ion source. A methanol concentration of 30-50% was found to give the best result in terms of sensitivities and S/N ratio. The method was successfully applied to the quantitative analysis of pantothenylethylether in a hair lotion. INTRODUCTION The combination of chromatography and spectrometry has been a useful tool for analysis of cosmetics, which are complex materials containing many components. For this pur- pose, gas chromatography-MS has been widely used (1,2), but it is not readily appli- cable to nonvolatile compounds, which account for a fairly large proportion of cosmetic ingredients. Although HPLC has also been widely applied to cosmetic analysis, qual- itative information that can be obtained through this analysis is very limited, even when HPLC is used in combination with selective detectors. The HPLC-MS has not been much used, probably because of the absence of general conditions applicable to a wide variety of cosmetic ingredients, which range from non-polar to highly polar compounds. When cosmetic products are to be analyzed by HPLC, mixtures of methanol and water with different ratios are most frequently used in a reversed-phase mode. Therefore, in order to establish a generally applicable condition for HPLC-MS analysis of cosmetics, we utilized CF-FAB MS as an interface, which has been reported by Caprioli et al. (3). 329

330 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The matrix was added without any changes in conditions by a post-column that has already been employed for routine analysis. We chose 30 compounds that are frequently formulated into cosmetics as so-called additives, such as antioxidants, preservatives, UV absorbers, and humectants, and as active ingredients, at 0.01-1.0% levels. First we established their detection limits by CF-FAB MS, using glycerin as a matrix. Based upon extensive screening studies, we then conducted optimization studies on both instrumental and analytical conditions for CF-FAB HPLC/MS, using a mixture of methanol and water as the mobile phase. We found that post-column addition of a matrix solution containing methanol and glycerin allowed us to adjust the methanol concentration at the ion source so as to obtain better sensitivity and S/N ratio. Although CF-FAB MS has been applied successfully to many compounds (4-9), the results of our comprehensive and systematic studies provide basic information to extend the applicability of the method, especially for analysis of components of complex mix- tures and unknown compounds. In addition, we applied the method to a quantitative analysis of hair lotion containing pantothenylethylether, which gave the highest sensitivity (5 pg) among the compounds studied here. EXPERIMENTAL FLOW INJECTION CF-FAB MS A micrometric pump (Milton Roy, FL) supplied the solvent to the injector. The injector was a Rheodyne 7410 (Rheodyne, CA) with a loop volume of 0.5 •I. This system was connected to a Finnigan MAT (Bremen, Germany) CF-FAB probe by means of a 1.5-m x 75-•m I.D. fused-silica capillary (SGE, Melbourne, Australia). The solvent was 50% (v/v) aqueous methanol containing 1% (v/v) of glycerin, and the flow rate was 7 pA/min. CF-FAB LC/MS This system, a schematic diagram of which is shown in Figure 1, consisted of an HPLC (glycerin / water) (glycerin / methanol) PUMP (mobile phase) ]COLUMN CFFAB MS I mixer splitter [ Figure 1. Schematic diagram of CF-FAB LC/MS system.