Water extractable sulfate-sulfur - ion chromatography chemical suppression of eluent conductivity

4 Water extractable sulfate-sulfur - ion chromatography (chemical suppression of eluent conductivity) 

The equipment and issues pertaining to this analysis are similar to those for soil chloride (see Method 5.5.1) using ion chromatography. The method is specific to sulfate, whereas ICPAES measures total S in the aqueous extracts. Accordingly, results will usually be lower for this analytical finish compared with Method 5.7.3. The only post-extraction preparation necessary, other than dilution, is the removal by filtration of particulate matter 0.20 pm. Since the concentration of SO -S can be influenced by biological transformations, aqueous soil extracts should be kept at 4°C if there is any delay (e.g. overnight) between completion of extraction and analysis. Under such conditions filtered aqueous samples should remain stable for at least 28 days (O Dell etal. 1984). The analysis can be undertaken in sequence with other anions (Dick Tabatabai 1979 O Dell etal. 1984). 

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