[Diffusion sampling of benzene present in the urine]

Benzene is a widely diffuse solvent; in the industrial environment benzene is currently present at concentrations of ppm. A valid method of biological monitoring that is easy to perform is need for assessing occupational and non-occupational exposures. A new method has been developed to evaluate low concentrations of benzene in urine samples by means of a diffusion sampling. The solvent is absorbed from the urine surface and concentrated on an absorbent substrate (Tenax) that is placed inside the vial. The solvent is thermically desorbed from Tenax and injected into a column (Thermal Tube Desorber-Supelco; 250 degrees C thermal flash; borosilicate capillary glass-column SPB-I 60 m length, 0.75 mm I.D., 1 micron film thickness; GC Dani 8580-FID). The method, which had not been previously employed for the determination of volatile organic substances in biological fluids, has a linear range which extends up to 40 micrograms/l, and gives results in excellent agreement with the conventional Head Space method, except in the low concentration region: the new method permits the quantitative determination of benzene quantities smaller than the detection limit of Head Space method connected with mass spectrometer (approximately 1 microgram/l). The detection limit was not exactly determined, but is estimated to be of 100 ng/l with 25 ml of urine sample.