CHEMICAL ENVIRONMENT IN ANIMAL BUILDINGS - DETERMINATION OF ORGANIC-ACIDS IN MANURE

A method has been developed for the determination of short-chained mon ocarboxylic acids C1-C6 in manure. The most important step in the proc edure is the highly selective enrichment of the acids with a liquid me mbrane technique, which here has been combined with derivatization usi ng pentafluorobenzylbromide and final analysis on GC. The liquid membr ane device consists of two PTFE blocks, each with an engraved channel, separated by a porous PTFE membrane impregnated with an unpolar liqui d. When the sample, with the acids as uncharged species, passes in the donor stream the acids can diffuse across the membrane and are irreve rsibly trapped and enriched in a stagnant alkaline/neutral solution in the acceptor channel. Linear calibration curves were obtained for the overall procedure with correlation coefficients generally between 0.9 96 and 0.999. The precision at the 50-100 mg/l level was ca 11% in bot h standard aqueous solutions and spiked manure samples and about the s ame for the different acids. The method was applied to manure samples from cattle-, swine- and hen houses. High concentrations of organic ac ids were found, for acetic acids up to 8 %. No general trend could be observed concerning differences in acid composition between cattle-, s wine- and hen manure. The acid concentrations seem to increase, when t he time for the fermentation process in the manure increases, which su ggests cleaning with relatively short time intervals as a way to minim ize corrosion in building constructions.