EVALUATION OF TO-15 METHOD EFICIENCY TO DETERMINE VOLATILE ORGANIC COMPOUNDS IN TYPICAL URBAN CONDITIONS

The efficiency of U.S. EPA TO-15 Method was evaluated under typical conditions of an urban environment with natural and anthropic emission sources. The performance criteria which should be met for a system to qualify, were fulfilled: a detection limit of <= 0.2 ng for all target compounds, replicate precision for a calibration standard and ambient samples within 20%. The stability of the target compounds during storage of sampled air in canisters was also evaluated at atmospheric pressure and relative humidity of 50%. Results show that, in the sampling conditions, compounds are not stable for more than a week. For validation experiments, samples were collected at the entrance of Tijuca National Park, located at the city of Rio de Janeiro. Isoprene was selected as a marker of biogenic emissions, and aromatic compounds were selected as markers of anthropogenic emissions, primarily vehicular emissions. Then, samples were collected in Saens Pena Square, a central area in the Tijuca District, in the northern part of the city, approximately 10 km from the entrance of Tijuca National Park. Volatile organic compounds were determined and the results were compared with previous data obtained in the same local using other methods.