| Capillary electrophoresis (CE), which couples classic electrophoresis and modernelectrophoretic separation with micro-column separation, is a new analytical technology withhigh resolution, short analysis time, small sample requirements and low cost. However, due tothe small injection volume and short optical path length for the most commonly used UVdetector, the detection sensitivity of CE is one order of magnitude lower than that of HPLC,which greatly limits its application in analysis of real samples. Off-line and/or on-line samplepreconcentrations are effective and economical methods to solve these problems..Sweeping-micellar electrokinetic chromatograph (Sweeping-MEKC), an on-line sampleconcentration technique, has certain characteristics of simple operation, low cost, not usingexpensive equipment and so on. Dispersive liquid-liquid microextraction (DLLME), anoff-line sample concentration method, is a method with many advantages such asenvironmental friendliness, little organic extraction agent used, rapidity, high-recovery andhigh enrichment factor, simplicity of operation and low cost. The methods ofsweeping-MEKC coupled with DLLME were mainly discussed in this dissertation. The twocombination technologies for the determination of CPs in red wine and PAEs in Chinese whitespirti had been established, and the major content of this study is as following:1. A method of dispersive liquid–liquid microextraction (DLLME) and reversed phaseliquid–liquid microextraction (RP-LLME) procedure coupled with sweeping-micellarelectrokinetic chromatography (sweeping-MEKC) was established to extract and determinethe three chlorophenols (CPs) compounds including pentachlorophenol (PCP),2,4,6-trichlorophenol (TCP) and2,4-dichlorophenol (DCP) in red wine. The influences of theparameters of two extraction steps and the electrophoresis conditions were investigated. Themethod had high enrichment factors, high sensitivity, good reproducibility and rapid analysistime. Under the optimum conditions, the three analytes showed satisfactory linearities overthe range of0.5~100μg/L (r≥0.985). The limits of detection (S/N=3) were in the range of0.035~0.114μg/L. The average recovery rates were in the range of75.2%~104.7%with therelative standard deviations (RSDs) not more than6.2%. Due to the low detection limit of thismethod and satisfactory recovery rates, these results indicated that the proposed method might be further applied for the determination of trace CPs in various sample matrixes and otherweak acidic organic contaminants.2. A simple, rapid, low organic solvent-consuming and sensitive method was proposedfor the analysis of phthalic acid esters (PAEs) in white spirit by using dispersive liquid-liquidmicroextraction (DLLME) coupled with sweeping-β-cyclodextrin modified micellarelectrokinetic chromatography (β-CD-MEKC). The influences of the parameters of DLLMEand the electrophoresis conditions were investigated. Under the optimum conditions, the totalresolution of four PAEs was within13min and satisfactory linearities (DEP,10~500ng/mL;DIBP and DBP,5~1000ng/mL; BBP,5~800ng/mL), low detection limits (0.4~0.8ng/mL)and acceptable recovery rates (89.6%～105.7%, RSD≤6.3%) were obtained. This methodshortened the migration time, and greatly improved the detection sensitivity under thecombination of DLLME with CE. Finally, the proposed method was successfully applied totwenty-two white spirits, and results showed that the dibutyl phthalate contents in55%ofsamples exceeded the Specific Migration Limit (SML) of0.3mg/kg established by thedomestic and international regulations. The method can provide a reference for thedetermination of PAEs in different aqueous samples. |
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