Determination of benzene, toluene, ethylbenzene, and xylenes in urine by purge and trap gas chromatography A method for determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in urine is described. Determination is performed by dynamic headspace (purge and trap) gas chromatography with photoionization detection. The features of the described method, i.e. detection limits of 15 -35 ng L -1 , relative standard deviations of 0.2 -10%, accuracy of 80 -100%, removal of interference of many compounds present in urine, sharp chromatographic peaks because of cryogenic refocusing, no sample preparation, make it convenient for biological monitoring of exposure to low levels of BTEX. However, the method is time-consuming and sophisticated.