Capillary electrophoresis determination of urinary muconic acid as a biological marker for benzene in cigarette smoke.

trans,trans-Muconic acid (MA), a benzene metabolite in urine, has currently been indicated as a biological marker for benzene in cigarette smoke. The available methodologies for MA present a few shortcomings, such as lack of specificity and labor-intensive sample pretreatment. In this work, a capillary electrophoresis method for separation, identification, and quantification of urinary muconic acid has been implemented. The electrolyte consisted of a 60-mM phosphate buffer solution (pH 7), containing 0.1 mM cetyltrimethylammonium bromide (CTAB) as an electroosmotic flow modifier. Urine samples from nonsmokers and smokers were filtered through a 0.22-micron membrane prior to injection in a 75 microns i.d. x 80 cm capillary. The analysis was conducted under constant voltage conditions of -30 kV and direct UV detection at 262 nm. The detection capability of the electrophoresis system was enhanced by employing a high-sensitivity optical cell, positioned at 60 cm from the injection port. The CE methodology presented an overall analysis time of less than 10 min, with 5 min spent for capillary conditioning and approximately 5 min for run completion. The method was found to be sensitive for the determination of MA down to 25 micrograms/L, with a percentage recovery of 100 +/- 8%, and suitable for discriminating urinary MA from nonsmokers and smokers.