Comparison of methodology for determination of ethylene dibromide in grains and grain-based foods

Three commonly used methods for determination of ethylene dibromide (EDB) in grains and grain products have been compared. EDB residues were extracted by soaking in hexane, triple co-distillation with hexane from an aqueous sample solution, and soaking in acetone-water (5 + 1). Each method was used for triplicate analyses of 12 samples containing incurred residues of EDB ranging from about 10 to 1000 ppb and representing whole grains (wheat and oats) and intermediate grain-based products such as corn meal and flour. The 4-day hexane soaking method extracted the least EDB. In some cases, this was half of the amount determined by the other methods. Levels from soaking in acetone-water were equal to, or up to 25% greater than, those from distillation. Although soaking for 2 days is required for whole grains in the method, a period of only 16 h was found acceptable for ground products. Results were obtained faster with the distillation method, but more analyst time per sample was required. A single distillation recovered about 80% (40-60% from wheat) of total EDB extracted by triple distillation. Foaming was reduced by the addition of concentrated H2SO4 to the aqueous hexane-sample mixture, plus stirring during distillation, thereby allowing complete recovery of the hexane.