Two-step stacking by sweeping and micelle to solvent stacking using a long-chain cationic ionic liquid surfactant.

Coupling of long-chain ionic liquid (LCIL)-based sweeping and micelle to solvent stacking (MSS) in CZE for anionic compounds was proposed. N-Cetyl-N-methylpyrrolidinium bromide (C16MPYBr) was used as a novel cationic surfactant. The capillary column was conditioned with poly(1-vinyl-3-butylimidazolium) bromide, a kind of polymeric ionic liquid, to obtain the anodic electroosmotic flow (EOF). There is a micellar solution (MS) zone which is prepared with C16MPYBr before the sample zone. The micelles penetrated into the sample zone, swept and transported the analytes toward the micelle to solvent boundary (MSSB). Meanwhile, a sufficient amount of methanol in the background solution (BGS) resulted in the reversal of effective electrophoretic mobility of analytes and completed the MSS. Under optimal conditions, good linearity (0.9988–0.9999) was obtained for model analytes in a wide linear range with limits of detection (LODs) from 0.025 to 0.25 mg/L. The intraday and interday repeatabilities (%RSD, n=5, 10) were acceptable in the range from 2.12 to 7.29%. 34 and 25 times increases in peak area sensitivity for benzoic acid (BA) and 2-nitrophenol (2-NP) and 60 times increase in peak height sensitivity for 4-chlorophenol (4-CP) were obtained. The proposed method is applied to analyze two spiked environmental water samples obtaining satisfactory recoveries.