Electrophoretic concentration and sweeping-micellar electrokinetic chromatography analysis of cationic drugs in water samples

• Simple and green off-line sample preparation by electrophoretic concentration of cationic drugs.
• Sweeping-MEKC analysis of acidified sample concentrate.
• Analyte concentration of four orders of magnitude with MDL in the pg/mL range in purified water.
• Analyte concentration of three orders of magnitude with MDL in the ng/mL range in waste water effluent.

Sample preparation by electrophoretic concentration, followed by analysis using sweeping-micellar electrokinetic chromatography, was studied as a green and simple analytical strategy for the trace analysis of cationic drugs in water samples. Electrophoretic concentration was conducted using 50 mmol/L ammonium acetate at pH 5 as acceptor electrolyte. Electrophoretic concentration was performed at 1.0 kV for 50 min and 0.5 kV and 15 min for purified and 10-fold diluted waste water samples, respectively. Sweeping-micellar electrokinetic chromatography was with 100 mmol/L sodium phosphate at pH 2, 100 mmol/L sodium dodecyl sulfate and 27.5%-v/v acetonitrile as separation electrolyte. The separation voltage was −20 kV, UV-detection was at 200 nm, and the acidified concentrate was injected for 36 s at 1 bar (or 72% of the total capillary length, 60 cm). Both purified water and 10-fold diluted waste water exhibited a linear range of two orders of concentration magnitude. The coefficient of determination, and intra- and interday repeatability were 0.991–0.997, 2.5–6.2, and 4.4–9.7%RSD (n = 6), respectively, for purified water. The values were 0.991–0.997, 3.4–7.1, and 8.7–9.8%RSD (n = 6), correspondingly, for 10-fold diluted waste water. The method detection limit was in the range from 0.04–0.09 to 1.20–6.97 ng/mL for purified and undiluted waste water, respectively.