Residual organic compounds fractionation from aqueous

Fractionation of Residue Organic Compounds from Aqueous Environmental Samples... 

Introduce a solution of 100 g. of sodium bisulphite in 200 ml. of water and continue the stirring, preferably for 10 hours with exclusion of air. A thick precipitate separates after a few minutes. Collect the bisulphite compound by suction filtration, wash it with ether until colourless, and then decompose it in a flask with a lukewarm solution of 125 g. of sodium carbonate in 150 ml. of water. Separate the ketone layer, extract the aqueous layer with four 30 ml. portions of ether, dry the combined organic layers over anhydrous magnesium sulphate, remove the ether at atmospheric pressure, and distil the residual oil under reduced pressure from a Qaisen flask with fractionating side arm (Fig. II, 24, 5). Collect the cyclo-heptanone at 64r-65°/12 mm. the yield is 23 g. 

The aqueous fraction was acidified to pH 1 with 6N HC1, and the small amount of humic acids which precipitated was removed by filtration. The filtrate was extracted three times with 100-ml portions of ethyl acetate. The organic extracts were combined, dried over anhydrous sodium sulfate, and filtered. The solvent was removed by rotary evaporation and the residue contained the freed byproducts from the hydrolyzed esterified and insoluble-bound compounds. 

The residual sediment after organic solvent extraction was extracted repeatedly with 0.2N NaOH to isolate the fulvic/humic acid fraction. Humic acid was then precipitated with hydrochloric acid to separate it from fulvic acid in the aqueous phase. Fulvic acid was purified by adsorption and subsequent elution from a column of Amberlite resin. Humic acid was purified by redissolving in NaOH and reprecipitation with hydrochloric acid. The residual sediment was then treated sequentially with hydrofluoric acid of increasing concentration to remove the silicates, washed several times with water and then dried to recover protokerogen (Stuermer et al, 1978). Procedure blank for each compound class fraction was dso combusted for carbon dioxide measurement. 

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