ABSTRACT
Some new types of microemulsion using phospholipids as the main surfactant were prepared for electrokinetic chromatography and the quantitative structure-retention relationship of neutral solutes in these microemulsion electrokinetic chromatography (MEEKC) systems was studied by solvation parameters model.By using dynamic coating capillary, and with dimethyl sulfoxide (DMSO) and dodecyl benzene as the marker of electroosmotic flow and microemulsion droplets, a total of 17 kinds of stable microemulsions containing soybean phospholipids or other surfactants were prepared and the linear salvation energy relationship equations were developed for these MEEKC systems with 26 small neutral compounds.The coefficients of linear solvation energy relationship (LSER) equations were used to evaluate the similarity of two MEEKC systems.Results indicated that LSER characteristics of phospholipids-MEEKC systems were similar to those of other microemulsion systems.The volume and hydrogen bond basicity of solutes were mostly contributed to the retention in MEEKC.The different types and concentration of oil phase had no evident influence on the retention.
ABSTRACT
A sensitive analytical method based on reversed microemulsion electrokinetic chromatography ( MEEKC) combined with on_line preconcentration technique was developed for the determination of polycyclic aromatic hydrocarbons ( PAHs ) in cosmetics. For six lipophilic PAHs analytes which are difficult to be separated under conventional conditions, three stacking techniques including large volume sample stacking ( LVSS) , dynamic pH junction and sweeping ( LVSS_DypH_sweep ) were combined to realize the efficient preconcentration and separation. Under the optimum conditions, including the microemulsion buffer with the composition of 2. 4%(w/w)SDS_0. 6% (w/w) octane_6. 6% (w/w)n_butyl alcohol_20 mmol/L NaH2PO4 ( pH 2 . 2 ) , HCB injection time of 20 s ( 16 kPa ) and sample injection time of 80 s ( 16 kPa ) , good enrichment effect was reached with the enrichment factors ranged from 25 to 80 , and the PAHs were analyzed successfully within 27 min. The developed method was used to analyze the PAHs in cosmetics. The recoveries ranged from 90 . 6% to 95 . 9%. The RSD values ( n=5 ) were less than 5 . 1%.