Flow analysis method for determining the concentration of methanol and ethanol in the gas phase using the nitrite...

This paper presents a flow determination method for low molecular weight alcohols (methanol, ethanol) in the gas phase using the nitrite formation reaction, which was developed from an earlier method using a glass bottle. In this method, the ambient air and nitrogen dioxide (1,000 ppmv) were allowed to continuously flow in a glass tube, which had been filled with 10 g of Pyrex glass beads. The flow rates of the ambient air and nitrogen dioxide were 30 and 20 cm3/min, respectively. The gas-phase alkyl nitrites produced by the dark reaction of atmospheric alcohols and nitrogen dioxide on the Pyrex glass beads were then analyzed by gas chromatography with an electron capture detector. The alcohol concentrations of the samples were calculated using a calibrated conversion factor for each alcohol to its nitrite. The detection limits for the methanol and ethanol are 0.7 and 0.5 ppbv, respectively. This flow method was used to determine the atmospheric alcohol concentrations and was found to have the advantages of a short sampling time and simple quantitative procedure compared with the previously reported method (glass bottle method). The feasibility of this method was also established.