A new method for determining the concentration of atmospheric alcohols using the nitrite formation reaction

A new method for measuring the concentration of atmospheric alcohols was developed and applied to ambient air samples. In the method, air samples were collected in 200 ml Pyrex glass bottles whose surface had been cleaned and treated with a chromic acid mixture. Alcohols in the sample were allowed to react in the dark with intentionally added nitrogen dioxide (200 ppm by volume (ppmv) concentration level) on the glass surface to yield corresponding alkyl nitrites. The concentration of the nitrite thus yielded is determined separately by gas chromatography (GC) with an electron capture detector (ECD). Alcohol concentration in the sample is calculated using a calibrated conversion factor of each alcohol to its nitrite. Detection limits for methanol, ethanol, and isopropanol are 0.9, 0.7, and 1.8 ppbv (parts per billion by volume), respectively, using 500 μl injection of the reaction mixture by this method. In order to examine the feasibility of this method for an ambient air sample, several measurements were done. Air samples were taken on a road with heavy traffic near the campus of Osaka Prefecture University. Concentration levels of methanol, ethanol, and isopropanol were 4–10, 3–25, and 1.5–20 ppbv, respectively. Diurnal variation of these alcohols’ concentration was also measured. Generally, alcohol concentrations were higher in the evening than those in the daytime, increasing up to the levels of 10–20, 10–25, and 10–20 ppbv for methanol, ethanol, and isopropanol, respectively.