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A cell-free preparation has been obtained from Saccharomyces cerevisiae which will synthesize ethyl acetate from ethanol and acetyl-CoA. Ethyl acetate synthesizing activity is stimulated by magnesium ions, the optimal concentration being 8 mM. Subcellular fractionation indicates that the enzyme is associated with material sedimenting at 105 000 Q.

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A stability-indicating procedure is described for the quantitative measurement of tiamulin hydrogen fumarate in animal feeds a t levels of 10 and 120 pgg-l. The tiamulin hydrogen fumarate is extracted from the feed with a solution of ethyl acetate in hexane (25% V / V ) in the presence of sodium carbonate solution (1% m / V ) . The tiamulin base is then backextracted into tartaric acid solution (0.1% m / V ) , which is introduced on to the column by loop injection. Owing to the very low ultraviolet absorption of tiamulin, large injection volumes were required in order to obtain a response suitable for quantitation. Injection volumes as high as 3 ml have been made without any significant broadening or distortion of the tiamulin peak.

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