An automated gas‐chromatographic measurement of carbon dioxide is described and its application to a biodegradation screening test procedure is demonstrated. The biodegradation test system consists of 20‐ml glass vials containing aqueous solutions of a test chemical and an acclimated microbial inoculum. The vials and their contents are sealed with rubber septa. At specified time intervals, the contents of selected vials are acidified. Subsequent automated headspace determination of carbon dioxide provides a measure of cumulative biological degradation. To demonstrate the validity of the overall test procedure, the biodegradabilities of eight organic compounds were measured: aniline, benzaldehyde, ethylenediaminetetraacetic acid, ethylene glycol, linear alkylbenzene sulfonate, nitrilotriacetic acid, p‐nitrophenol and N‐methylaniline. Biological degradation was also monitored by measuring residual test chemical concentrations. There was excellent internal consistency of results by comparison of carbon dioxide evolution values with specific chemical analyses. Both the results of carbon dioxide measurements and specific chemical analyses are discussed in relation to literature values derived from similar screening test procedures. It is concluded from this study that automated headspace determination of carbon dioxide has several advantages over existing test methods. It is further concluded that application of this headspace procedure in the screening test described provides an accurate, albeit conservative, estimate of biodegradability, with positive results indicating a low potential for environmental persistence.

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