One solution is to use a specific column,
which is available commercially but can be very expensive
to use. In order to explore more economic methods, some
chromatographic researchers have developed on-line sample
pretreatment, including hyphenation of gas-diffusion separation,
which is based on the diffusion separation of sulfur
dioxide following on-line oxidation with hydrogen peroxide
to sulfate and a final determination of sulfate using ion pair
chromatography