The use of sodium dodecyl sulfate, urea, ß-cyclodextrin, and methanol as additives to the electrophoretic medium containing a NaHPO-boric acid buffer in the micellar electrokinetic capillary chromatography of benzene, toluene, ethylbenzene, and three isomers of xylene (collectively known as BTEX) was investigated. The results showed that with the addition of sodium dodecyl sulfate only, higher selectivity and sensitivity and shorter migration time could be achieved, which consequently resulted in better separation of BTEX studied. For this buffer system, good linearity (R>0.99) was found over the range of 5 to 500 μg m1 for individual BTEX compound and separation time of less than 5 min for BTEX was possible. © 2004 Taylor & Francis Group, LLC.