Determination of chlorophenols in human urine based on the integration of on-line automated clean-up and preconcentration unit with micellar electrokinetic chromatography

A new method was developed and validated for the determination of chlorophenols in human urine by using micellar electrokinetic chromatography (MEKC) coupled via a mechanic arm to an on‐line automatic clean‐up and preconcentration unit for urine samples. Separation is accomplished by using a selective buffer consisting of 15 mM borate, 25 mM phosphate and 100 mM sodium dodecyl sulfate (SDS) at pH 9.1 in addition to a positive power supply of 25 kV at 18°C. The proposed capillary electrophoresis (CE) method allows the separation of 11 chlorophenols within 7 min with a repro ducibility as relative standard deviation (RSD) between 2.6% and 7.2%, and limits of detection (LODs) between 0.08 and 0.46 μg/mL for all chlorophenols. Urine samples were previously hydrolyzed with 37% HCl at 80°C for 60 min and then cleaned on a C‐18 mini‐column. Recoveries ranged from 58% to 103%. The preconcentration treatment affords limits of determination between 4 and 12 ng/mL for all chlorophenols except pentachlorophenol and 4‐chlorophenol, which could not be determined. The overall analysis time, including on‐line clean‐up, preconcentration and electrophoretic separation is 20 min per sample.