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New Test Method for Determining Biodegradability of Lubricants

April 01, 2013
Ben Müeller-Zermini
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New Test Method for Determining Biodegradability of Lubricants: CEC-L-103-12

In July 2012 the European organization CEC (Coordinating European Council) released a new test method for testing biodegradability of lubricants in natural environment. The new test is called CEC-L-103-12. The CEC organization is known to the world of environmental friendly lubricants, because of the test method CEC-L-33-A-93, which was the very first test method for testing biodegradability of lubricants. Unfortunately this test method became more and more unpopular because of the use of the chlorofluorocarbon (CFC) containing solvent, which was necessary to quantify the oil content by infrared analysis. The CEC technical development group TDG-L-103 found a way to avoid the use of these hazardous chemical. Instead of infrared spectroscopy they used high temperature gas chromatography to quantify the oil content. In addition they were able to abstain from the toxic mercury chloride which was necessary to prepare the toxic flasks in CEC-L-33. In a round robin test which was performed in six laboratories it could be shown that the precision of the new test method is even better than the precision of CEC-L-33.

The test methods CEC-L-33-A-93 and CEC-L-103-12 were especially developed for testing the biodegradability of poor water soluble lubricants. Nowadays often the OECD 301 test methods are used for testing biodegradability of these products. But the OECD 301 test methods originally were developed for water soluble chemicals. If we want to use them for testing poor water soluble substances, we have to introduce these substances into the aqueous phase of the test system. Of course there is a guideline to do this. It is called ISO 10634 “Guidance for the preparation and treatment of poorly water soluble organic compounds for the subsequent evaluation of their biodegradability in an aqueous medium”. In this guidance there are described five different methods to introduce the sample into water. But each method leads to a different result. In addition biodegradation rate depends on stirring velocity! This relationship was discovered by a group of scientists among A. DeMorsier in 1987 (Chemosphere, Vol. 16, No. 4, pp 833-847, 1987). The only official round robin test of the OECD 301 tests was performed in 1988. The final report of the chairman M. Hashimoto from MITI institute is accessible for public. Test substances in this round robin test only were water soluble, pure chemicals. The OECD 301 A, which measures DOC (Dissolved Organic Carbon), showed very good repeatability (results varied between about 90% and 110%) and it showed that all test substances are biodegradable within 28 days. Unfortunately this “DOC Die-Away” test method can only be used for water soluble test substances. All respirometric test methods (OECD B, C, D and F) showed very bad reproducibility for all test substances, here the degradation rates varied between 0% and 120%! The recommendation of the chair man was in case of water soluble test substances to use the “DOC Die-Away” method, the other methods need to be revised. But up to now we couldn’t find any revision or a new round robin test for these test methods.

Therefore we think the only reliable test method for testing biodegradability of lubricants is the new CEC-L-103-12. More information about this test method can be found on the CEC homepage http://www.cectests.org.

Ben Müeller-Zermini is the author of this article.

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