Determination of methanol and ethanol by gas chromatrography following air sampling onto florisil cartridges and their concentrations at urban sites in the three largest cities in Brazil

Abstract

A new sampling protocol was developed to determine methanol and ethanol in the gas phase, at low concentration levels, in urban atmospheres. The procedure involves collection of air samples (20.0–30.0 l) with three florisil cartridges connected in series, at a flow rate ranging from 1.0 to 2.0 l min−1 and subsequent elution of the alcohols with water. Separation and quantification were done by gas chromatography (GC) coupled with a flame ionization detector, ‘SPI’ injector and column DB WAX (30 m×0.53 mm×1 μm). The minimum mass detected by the method, based on two times the average background mass on the blank cartridges, was 0.3 μg for both alcohols which, for a sampled volume of 30 l, resulted in detection limits of 7.6 and 5.3 ppbV for methanol and ethanol, respectively. The determined alcohol concentrations, in 42 different samples from the three largest cities in Brazil—São Paulo, Rio de Janeiro and Salvador—ranged from 72 ppbV to below the detection limit for methanol and from 355 to 12 ppbV for ethanol.