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Ambient levels of formaldehyde and BTEX (benzene, toluene and xylene) compounds were monitored at seven residential areas in Xicheng District, Beijing, during the period of November-December 2009. Formaldehyde was collected using 2, 4 dinitmphenyihydmzine (DNPH) modified silica tube and analyzed by HPLC. BTEX compounds were collected with activated carbon tube and analyzed by GC-FID. The concentrations...
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