Abstract
Several carboxylic acids produced in the biodegradation process of n-butyl alcohol by activated sludge were determined by liquid chromatography using a flow coulometric detector.
The eluate from a strong acid type-cation exchanger with an aqueous solution of 5% methylcellosolve was mixed with a solution consisting of 10-2 M p-quinone, 10-3 M hydroquinone and 10-1 M potassium chloride, and the resulting solution was introduced to a carbon-cross anode. A mixed solution of 0.5 M potassium iodide, 0.2 g/l sodium sulfite and 10-3% v/v Triton X-100 was introduced to an Ag-AgI cathode. The hydrogen ion yielded by the ionization of a carboxylic acid was reacted with p-quinone at the constant voltage of +0.45 V vs. Ag-AgI and the coulomb in the reduction to hydroquinone was measured for the determination of the carboxylic acid.
The sample solution was filtered with millipore filter No. GSWP-4700(pore size, 0.22 micron) and the filtrate was bubbled with nitrogen gas after removal of bicarbonate ion by addition of hydrochloric acid, because the chromatogram of the bicarbonate ion shows the same elution time with n-butyric acid.
When oxygen was dissolved sufficiently in the activated sludge, the carboxylic acid was not found in the biodegradation process. When an inhibitor had been added under the conditions described above, acetic and n-butyric acids were found by addition of 2 μg/ml cupric ion as shown in Fig. 5B. When 250 μg/ml formaldehyde had been added, n-butyric acid was found after one hour as shown in Fig. 5C and formic acid after three hours as shown in Fig. 5C. Under the conditions of great lack of the dissolved oxygen, acetic and n-butyric acids were found as shown in Fig. 5D. In the absence of air, acetic, n-propionic and n-butyric acids were found after three days from the addition of 1000 μg/ml n-butyl alcohol as shown in Fig. 5E. They seemed to be derived from autolysis of the activated sludge.
