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Determination of 'ready' biodegradability: carbon dioxide (C02) evolution test (modified Sturm test) with FORMAMIDOPROPYLBET AINE.

The study procedure was based on EEC directive 92/69, C.4-C, December 1992, OECD guideline No. 301 B July 17, 1992 and ISO Standard 9439 (1999). The batch of FORMAMIDOPROPYLBETAINE consisted of FORMAMIDOPROPYLBETAINE (40.1%), water (56.1%) and sodium chloride (3.8%). FORMAMIDOPROPYLBETAINE was tested in duplicate at 102 mg per 2 litres, corresponding to 10 mg TOC/L. The organic carbon content (20.5%) was based on the composition and molecular formulae. The Theoretical CO2 production (ThCO2) of FORMAMIDOPROPYLBETAINE was calculated to be 0.75 mg CO2/mg. The study consisted of six bottles: 2 blank controls (no test material), 2 test bottles (FORMAMIDOPROPYLBETAINE, 51.1 mg/L), 1 positive control (sodium acetate, 40.1 mg/L) and 1 toxicity control (FORMAMIDOPROPYLBETAINE, 51.1 mg/L; plus sodium acetate, 40.1 mg/L). A stock solution of 1 g FORMAMIDOPROPYLBETAINE/L was prepared by dissolving 1002.6 mg of FORMAMIDOPROPYLBETAINE in 1 litre Milli-RO water. Magnetic stirring (12 minutes) was used to accelerate dissolving and to ensure homogeneity. The stock was a clear and colourless solution. Aliquots of 102 ml of the stock solution were added to the test medium, containing the microbial organisms, of test substance bottles A and B and the toxicity control. The test solutions were continuously stirred during the test, to ensure optimal contact between the test substance and the test organisms. The relative degradation values calculated from the measurements performed during the test period revealed 31 and 39% degradation of FORMAMIDOPROPYLBETAINE, for the duplicate bottles tested. Thus, the criterion for ready biodegradability (at least 60% biodegradation within a 10-day window) was not met. In the toxicity control, FORMAMIDOPROPYLBETAINE was found not to inhibit microbial activity. Since all criteria for acceptability of the test were met, this study was considered to be valid. In conclusion, FORMAMIDOPROPYLBETAINE was not readily biodegradable under the conditions of the modified Sturm test presently performed.