Sulfur, biological removal from petroleum

The oxides of sulfur create global pollution problems because they have longer lifetimes in the atmosphere than the oxides of nitrogen. Some of the SO2 and SO3 in the air originates from biological processes and from volcanoes, but much comes from the oxidation of sulfur in petroleum and in coal burned for fuel. If the sulfur is not removed from the fuel or the exhaust gas, SO2 enters the atmosphere as a stable but reactive pollutant. Further oxidation by radicals leads to sulfur trioxide ... 

Derivatives are often used in lipid chemistry to prepare fatty acid methyl esters needed to determine the fatty acid composition of lipids. Fried et al. (1992) published a technique on the transesterification of 500-mg samples of snail tissue. Because the technique is applicable to other biological tissues and fluids, it is presented herein. Lipids were extracted from snail bodies with 10 ml of chloroform-methanol (2 1) the extracts were filtered through a plug of glass wool contained in a Pasteur pipet, and nonlipid contaminants were removed by extraction with 8 ml of Folch wash (0.88% aqueous KCl). The lipid-containing lower phase was separated and evaporated just to dryness under a stream of nitrogen at room temperature. The total lipid sample was dissolved in about 30 ml of methanol, and 0.5-1.0 ml of concentrated sulfuric acid was added. The mixture was refluxed for 1 h the formed fatty acid methyl esters were extracted with 30-40 ml of petroleum ether and the extract dried over anhydrous sodium sulfate. The fatty acid methyl esters were concentrated on a Rotoevaporator at 40°C and the volume reduced to 1 ml. The fatty acid methyl esters can be separated by TLC on silica gel impregnated with silver nitrate (Christie, 1982). 

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