Noritaka Oyamada

Determination of bromate in foods by gas chromatography

An improved method for quantitative determination of bromate in bread and fish paste products was established.A sample was homogenized with distilled water and made up to 200ml after centrifugation. The supernatant was filtered and n-butanol-ethanol (2:1) mixture was added to 10ml of the filtrate. The mixture was allowed to stand for 10min then centrifuged to remove the precipitate. DEAE-Sephadex A-25 suspension and acetic acid were added to the supernatant, and the mixture was stirred for 5min. After centrifugation, the supernatant was subjected to the same procedure with DEAE-Sephadex A-25 suspension. The DEAE-Sephadex A-25 was mixed with ethanol, and rinsed twice with ethanol, 5.0% acetic acid and distilled water. The solid was packed in a chromatocolumn, and bromate was eluted with 30ml of 30% potassium chloride solution. Two ml of 4×10-3M styrene monomer solution (washed with 1% sodium hydroxide solution before use), 1ml of 0.01M potassium bromide solution and 1ml of sulfuric acid were added to the effluent, and the whole was shaken vigorously. Styrene bromo derivative was extracted with 2ml of n-hexane, and bromate was determined by ECD-GC.In this method, it was found that bromate in foods could be determined with a recovery of 80-92.3% and a variation coefficient of 6.2-2.6%. The detection limit was 0.01μg/g.

Determination of Hydrogen Peroxide in Foods by the 3-Methyl-2-benzothiazolone Hydrazone Method

An advanced method of determination of hydrogen peroxide in foods has been investigated.Hydrogen peroxide in sample was extracted with two times volume of methanol. 1ml of the extract containing hydrogen peroxide was transferred into a 20ml of test tube, and 3ml of distilled water and catalase solution (2, 000 I. U.) were added to the extract in the test tube and warmed for 15min at 37°C to produce the formaldehyde quantitatively. Then 1ml of 0.4% 3-methyl-2-benzothiazolone hydrazone hydrochloride solution was added into the test tube and warmed again for 25min at 37°C, and 5ml of 0.2% ferric nitrate solution was added, then the test tube was allowed to stand for 5min at room temperature for complete development of the color. The reaction mixture was diluted to 20ml with acetone. The absorbance of the solution was determined at 635nm of the wave length.Under the condition described above, it was found that the hydrogen peroxide in some kind of food could be determined with recovery 97-107% and variation coefficient of about 5%.