Benzene in Soft Drinks – Analytical Artifact?

An update on the benzene story from last month.

Chemical & Engineering News: Latest News – Dispute Over Benzene In Drinks

In late 2005, FDA began analyzing beverages containing benzoate and ascorbic acid. The majority of samples contained either no detectable benzene or levels below 5 ppb, says Robert E. Brackett, director of FDA’s Center for Food Safety & Applied Nutrition. FDA’s results are preliminary. After its survey is complete, the agency will determine what, if any, additional action is necessary, Brackett wrote to EWG. Changes in FDA’s analytical procedures may account for the differences in results. To collect benzene in the earlier tests, FDA used a purge-and-trap method, in which the samples were heated to 100 °C for 30 minutes. Recently, the agency has been using a static-headspace methodology, which does not involve much heat. In the earlier tests, the high heat was probably creating benzene, says an FDA source who asked not to be identified.

The explanation seems to make sense. Low level analysis is riddled with instances such as these, where the analyte you’re looking for is  introduced into the sample after the fact. It is impossible to decide without looking at the protocol whether this happened or not. Since the source of the benzene is from the reaction of ascorbic acid (aka Vitamin C) and benzoate salts, notably sodium benzoate, it would have been clear to anyone doing the analysis to avoid conditions that would result in the formation of benzene during the analysis, or maybe not…

Static Headspace analysis usually involves some heating as well, at much lower temperatures for shorter periods of time, though in the case of something as hydrophobic as benzene, not much heat would be required. So, the artifacts in static headspace would in this case be lower than in purge and trap analysis.

Still not a concern in the grand scheme of aggregate benzene exposure.

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