Selective determination of ionised bromide and organic bromides in Foodstuffs by gas‐liquid chromatography with special reference to fumigant residues

Abstract

Abstract A number of methods in common use for determining amounts of bromine‐containing compounds occurring as residues in foodstuffs, primarily as a result of commodity or soil fumigation, do not distinguish between bromide ion and organically bound bromine. Although such compounds may differ widely in their toxicity, national and international schedules have included tolerances for total bromide determined as ‘inorganic bromide’. A method is described in which ionised bromide in foodstuffs is quantitatively converted to 2‐brompethanol (ethylene bromohydrin) by reaction with ethylene oxide in an acid medium. The 2‐bromoethanol produced is determined in processed extracts by gas‐liquid chromatography. Residual methyl bromide and ethylene dibromide (1,2‐dibromoethane), neither of which react with ethylene oxide under the conditions prescribed, are separated and determined concurrently. With foodstuffs which did not contain organo‐bromine compounds, good agreement was observed between results obtained by the gas chromatographic method and by total bromide determination involving alkali digestion, controlled ashing, extraction of ash and wet oxidation. In the light of the more specific methods of determination now available, some clarification in tolerance schedules for residual bromine compounds in foodstuffs is suggested.