Intercomparison of the measurements of oxalic acid in aerosols by gas chromatography and ion chromatography

Oxalate, the anion of oxalic acid, is one of the most abundant measurable organic species in atmospheric aerosols. Traditionally, this bifunctional species has been measured by gas chromatography (GC) after derivatization to butyl ester and by ion chromatography (IC) without derivatization. However, there are few published comparisons of the two techniques. Here, we report the results of an intercomparison study for the measurement of oxalic acid in Arctic aerosols (<2.5 μm, n = 82) collected in 1992 using GC and IC. The concentrations of oxalic acid by GC ranged from 6.5–59.1 ng m−3 (av. 26.0 ng m−3, median 26.2 ng m−3) whereas those by IC ranged from 6.6–52.1 ng m−3 (av. 26.6 ng m−3, median 25.4 ng m−3). They showed a good correlation (r = 0.84) with a slope of 0.96. Thus, observations of oxalate obtained by GC employing dibutyl esters are almost equal to those by IC. Because the accuracy of oxalic acid by GC method largely depends on the method used, it is important to strictly examine the recovery in each study.