On-line Preconcentration for Sensitive Analysis of PAHs in Cosmetics by Reversed Microemulsion Electrokinetic Chromatography

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 p H junction and sweeping( LVSS-Dyp H-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 Na H2PO4( p H 2. 2),HCB injection time of 20 s( 16 k Pa) and sample injection time of 80 s( 16 k Pa),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%.