Extraction conditions of organic acids in aqueous solution

IWASE Hiroshi, SUGIYAMA Taeko

doi:10.2116/bunsekikagaku.24.668

Volatile and non-volatile organic acids in aqueous solution were extracted with ether in the soxhlet extractor to examine the relationship between extraction time and recovery. All reagents used were of analytical grade. Volatile organic acids (acetic, propionic, butyric and n-valeric acids) and non-volatile organic acids (lactic, oxalic, malonic, fumalic, succinic, maleic, glutaric, α-ketoglutaric, malic and citric acids), 10 mg each, were dissolved in 50 ml of 3N sulfuric acid and then extracted with 100 ml of ether on a water bath at 55°C. The extract was dried over anhydrous sodium sulfate and concentrated to 20 ml on a water bath at (4045)°C. A half of the extract was concentrated almost to dryness on a water bath at (4045) °C and esterified for the analysis of non-volatile organic acids. The other half was employed for the analysis of volatile organic acids without esterification. The recovery of volatile organic acids reached the maximum after 3 hours of extraction and then decreased with increasing extraction time. This fact suggests that volatile organic acids were considerably evaporated during the extraction. It was also found that evaporation to (23) ml of the extract gave higher recovery than evaporation to complete dryness. Non-volatile organic acids, except for malic and citric acids, were almost completely extracted by the 6 hour extraction.

Extraction conditions of organic acids in aqueous solution

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