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 chlorophe nols in human urine by using micellar electrokinetic chromatography (MEKC) coupled via a mechanic arm to an on-line automatic clean-up and preconcentr ation unit for urine samples. Separation is accomplished by using a selecti ve buffer consisting of 15 mM berate, 25 mM phosphate and 100 mM sodium dod ecyl sulfate (SDS) at pH 9.1 in addition to a positive power supply of 25 k V at 18 degrees C. The proposed capillary electrophoresis (CE) method allow s the separation of 11 chlorophenols within 7 min with a reproducibility as relative standard deviation (RSD) between 2.6% and 7.2%, and limits of det ection (LODs) between 0.08 and 0.46 mu g/mL for all chlorophenols. Urine sa mples were previously hydrolyzed with 37% HCl at 80 degrees C for 60 min an d then cleaned on a C-18 mini-column. Recoveries ranged from 58% to 103%. T he 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-li ne clean-up, preconcentration and electrophoretic separation is 20 min per sample.