Headspace determination of evolved carbon dioxide in a biodegradability screening test.

A headspace method to measure the carbon dioxide evolved in a screening biodegradability test is described. Use was made of conventional serum bottles, sealed with butyl rubber septa, through which headspace samples were taken after acidification and equilibration of the test solution. For each determination a serum bottle was sacrificed. The gas samples were injected directly into the reaction chamber of a carbon analyzer. Eighteen chemicals varying in solubility and biological properties were submitted to the test. Where possible, mineralization of test compounds was monitored through dissolved organic carbon analysis in addition to CO2 analyses. The reliability of the method was verified by comparing the measured concentration of dissolved inorganic carbon of a standard sodium carbonate solution with values calculated from measured concentrations of carbon dioxide in the headspace after acidification. Results of biodegradability testing are discussed in view of the suitability of the method to poorly soluble compounds.