Solid-phase extraction, sample stacking and capillary zone electrophoresis for the analysis of urinary polycyclic aromatic hydrocarbon metabolites

A capillary zone electrophoresis method is presented for the analysis of six biomarkers of polycyclic aromatic hydrocarbons in urine samples. Baseline resolution of 2-hydroxyfluorene, 2-hydroxynaphthalene, 1-hydroxypyrene, 9-hydroxyphenanthrene, 3-hydroxybenzo[a]pyrene, 4-hydroxybenzo[a]pyrene and 5-hydroxybenzo[a]pyrene was achieved in approximately 17 min with a 20 mM borate buffer prepared in 50% methanol-water (volume/volume). Competitive limits of detection were obtained for all the studied metabolites using commercial instrumentation equipped with an ultraviolet-visible absorption detector. Detection at the sub-parts-per-billion concentration levels was made possible via sample pre-concentration based on solid-phase extraction and sample stacking. Solid-phase extraction was performed with the aid of a twelve port vacuum manifold. Sample stacking was carried out in methanol, i.e. the eluting solvent from the solid-phase extraction procedure. To the extent of our literature search, this is the first application of sample stacking to the analysis of monohydroxy-polycyclic aromatic hydrocarbons in urine samples. Metabolite recoveries varied from 93.2 +/- 7.7% (5-hydroxybenzo[a]pyrene) to 108.7 +/- 7.8% (2-hydroxynaphthalene). Limits of detection were at the trace level ranging from 0.99 ng mL(-1) (3-hydroxybenzo[a]pyrene) to 8.54 ng mL(-1) (2-hydroxynaphthalene). The new method was found to be free of interference from four pharmacological drugs - naproxen, ibuprofen, diclofenac and amoxicillin - that might be found in urine samples of unhealthy individuals.