Machinery Lubrication magazine published by Noria Corporation
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when the resulting carbon dioxide is measured, the shape will be somewhat different due to the side reaction into proteins and the time-consuming dying-off process of the biomass produced. This should be noted when comparing the results of oil removal tests with other methods measuring carbon-dioxide production. Test Development The establishment of a new test method for biodegradability began in late 2008 with the formation of the CEC Technical Development Group L-103. It was comprised of three active laboratories and a few industry experts. The group was charged with keeping the basic principles and advantages of the CEC-L- 33-A-93 test, such as having a clearly defined oil incorporation procedure, using reference oils, and being suitable and proven for all types and chemistries of oils on the market, especially all types of bio-lubes. In addition, the group was to avoid hazardous solvents, exceed the L-33 test in repeatability and reproducibility, and match the test quality and surveillance criteria of the 2001 guidelines set by the CEC. Just like the CEC-L-33-A-93 test, the new test's basic prin- ciple involves preparing a "mineral medium" (similar to natural surface water) that contains some mineral salts and natural micro-organisms. A small volume of oil and a carrier are added to prepare the test flasks, with biocide used for poisoned flasks and no addition made to neutral flasks. The oil contents of these flasks are analyzed and compared on the starting day and after 21 days of incubation in the dark with mild shaking at 25 degrees C. In all, 15 flasks are prepared for each candidate and reference oil — five for instant analysis and 10 for analysis after 21 days of degradation. In the initial version of the CEC-L-33 test, the carrier material used to introduce the test oil into the aqueous medium was carbon tetra-chloride. Ethylene tetra-chloride or Freon was prescribed after 1993. The same hazardous solvents were also used to extract the non-degraded oil portion for quantitative infrared spectroscopy analysis after three weeks. Excluding the use of such solvents was found to be a significant challenge in the L-103 test development. Eventually, high-temperature gas chro- matography was employed for the analytical evaluation of oil concentrations instead of infrared spectroscopy. Gas Chromatography Conventional gas chromatography (GC) is a good tool for qualitative and quantitative analysis as well as for producing simulated boiling curves of organic material with a minimum volatility. Lubricants of low and medium viscosity are also suit- able for GC analysis but not heavy materials and esters. High-temperature GC is a development of the last 10 years that has widely overcome these limitations and works well with all types of lubricating oils. Even polymeric components can be analyzed with good precision. Modern high-temperature GC INdUstrY FoCUs Preparation of test f lasks for the new biodegradability test 24 March - April 2014 | www.machinerylubrication.com Kinetics of biodegradation