An Automated Field Instrument for The Determination of Acidic Gases in Air

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Abstract
An automated field instrument is described for the continuous measurement of soluble acidic gases in ambient air. Sampling of the gases is carried out by using a wet-rotating annular denuder filled with an aqueous carbonate absorption solution. After addition of internal standard, the absorption stream from the denuder is led through one of two injection loops of an ion-chromatographic system. Separation is carried out on a Dionex lonPac AS-12A analytical column with suppressed conductivity detection. While one sample is analysed, a parallel injection loop of the chromatograph is filled with a next sample. In this way, air concentrations of HCl, HONO, HNO3 and SO2 can be obtained at approximately 20 min intervals. Detection limits are 0.1 μ/m3 for HCI and HONO and 0.2 μ/m3 for HNO3 and SO2. The applicability of the system is demonstrated in a measurement campaign at Petten, The Netherlands.