In order to measure directly a biodegradation rate of an organic compound, a radioactive carbon isotope 14C must be organochemically enriched in a sample first. Next, the sample enriched with the radioactive carbon isotope 14C is subjected to biodegradation, and a radiation dose of carbon dioxide generated in biodegradation is measured with a scintillation counter to determine an absolute amount of the radioactive carbon isotope 14C in carbon dioxide generated in biodegradation of the organic compound. A ratio of the absolute amount of the radioactive carbon isotope 14C in carbon dioxide to an absolute amount of the radioactive carbon isotope 14C in the 14C-enriched sample used is calculated, to thereby determine the biodegradation rate of the organic compound.
However, in the measurement method, a series of measuring operations must be performed in a space provided with measures against radiation because radioactive 14C is used. Thus, the measurement method has problems in that measurement of a radiation dose of carbon dioxide generated in biodegradation requires a long period of time, and that measurement errors are observed by disturbance of background radioactivity or the like in measurement of the radiation dose.
Therefore, development of a method of measuring a biodegradation rate of a non-natural organic compound rapidly and accurately without enriching a measurement sample with an expensive radioactive carbon isotope 14C and without providing any special measures against radiation has been desired.