ABSTRACT
Supercritical fluid chromatography (SFC) combines the hig h diffusion coefficients of gas chromatography (GC) and the solubility propertie s of liquid chromatography (LC). SFC generally requires lower temperatures for chromatographic separations and thus is more suitable for analyzing thermally l abile compounds including a number of metal chelates and organometallic compound s. SFC also allows interfacing between supercritical fluid extraction (SFE) and chromatographic analysis of metal-containing compounds. A large number of metal chelates and organometallic compounds can be separated b y SFC. This article summarizes SFC separation of various chelates of transitio n metals, heavy metals, lanthanides and actinides as well as organometallic comp ounds of lead, mercury and tin reported in the recent literature. This articl e also discusses SFC detection systems and the determination of solubility of or ganometallic compounds by SFC.
ABSTRACT
Objective To investigate the antibacterial performance of silicone quaternary ammonium microemulsion in cosmetics.Methods The bacteriostatic effects of three preservatives(0.10% silicone quaternary ammonium microemulsion,silicone quaternary ammonium emulsion and silicone quaternary microemulsion) were compared in terms of plate culture count.Three preservatives were diluted to 0.1,0.2,0.4,0.6,0.8,1.0,1.5,2.0,2.5,3.0,3.5,5.0 g/L respectively,and the minimal inhibitory concentration was explored.The antibacterial and anti-fungi ability of the three preservatives was compared based on the microbial challenge test of 28 days.The bacteriostasis kinetics of the Escherichia coli(E.coli) was studied with the turbidimetry.Results The bacteriostasis rate of 1.0 g/L silicone quaternary ammonium microemulsion,silicone quaternary ammonium emulsion and silicone quaternary microemulsion were 100.00%,91.16% and 84.66%,respectively.The minimum bacteriostasis concentration of silicone quaternary ammonium microemulsion was 1.0 g/L for E.coli and was 0.8 g/L for Staphylococcus aureus,respectively.The results of microbial challenge experiments indicated that silicone quaternary ammonium microemulsion could pass both the antibacterial and the anti-fungi tests.Silicone quaternary ammonium emulsion could also pass the antibacterial test but failed in the anti-fungi test.However,silicone quaternary microemulsion failed in the both tests.The growth rate of E.coli was inhibited in a low level by silicone quaternary ammonium microemulsion.Conclusion Silicone quaternary ammonium microemulsion can effectively inhibit the common bacteria in cosmetics.