A simple and sensitive method was developed for the quantitative determination of total bromine in cereals. 2-Bromo-3-pentanone derived from the reaction of bromine with 3-pentanone was quantitated by gas chromatography (GC) with an electron capture detector (ECD).
A 2g sample was ashed with 0.2g of anhydrous sodium carbonate and 5ml of alkaline monoethanolamine solution. The ached residue was dissolved in 10ml of 0.1N sodium hydroxide solution. After neutralization with 2N sulfuric acid, the solution was made up to 20ml with water. This diluted solution was used as the sample solution. Ten ml of the sample solution was transferred to a separatory funnel. One ml of 5% 3-pentanone solution, 1ml of 0.1M potassium permanganate solution and 1ml of 10N sulfuric acid were added successively. Bromide ion was oxidized and the liberated bromine was reacted quantitatively with 3-pentanone. The resulting 2-bromo-3-pentanone was extracted with 10ml of n-hexane and determined by ECD-GC.
The recovery of bromide added to rice and wheat flour was ca. 86%, and the detection limit was 0.05μg/g.