On-Line Concentration of Neutral Analytes for Micellar Electrokinetic Chromatography. 5. Field-Enhanced Sample Injection with Reverse Migrating Micelles

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Abstract
Elementary conditions for the on-line concentration of neutral analytes by field-enhanced sample injection with reverse migrating micelles for micellar electrokinetic chromatography is presented. Acidic phosphate buffers containing micelles of sodium dodecyl sulfate are utilized as both sample solvent and separation solution. After the capillary is conditioned with a separation solution, a water plug is hydrodynamically injected to achieve field enhancement at the injection end of the capillary during injection by application of voltage. A model is provided to give insight into the stacking scheme. Significant detector response improvements are confirmed experimentally. Moreover, utility of the technique for the analysis of a real sample is tested using urine spiked with testosterone and progesterone.