Potassium bromate is an odorless and tasteless white crystal that is commonly used in the baking industry. It is often added in flour and flour products to improve the product quality. It acts by oxidizing thiol groups of the gluten protein in flour and in the process forming disulfide bonds. The overall effect is to make bread rise in the oven, and increase loaf volume and texture. However, potassium bromate is considered a carcinogenic and nephrotoxic substance. Bromate has been listed as a potential carcinogen at low levels by the International Agency for Research on Cancer (IARC). Due to its hazardous properties, the concentration of bromate must be carefully monitored in bread. Ion-exchange chromatography with suppressed conductivity detection is the most commonly applied technology for the bromate measurements. However, conductivity detection has low selectivity, especially when applied to complex food matrices in which many compounds are ionic and thus can possibly interfere with bromate detection. Here we developed a new method using ion chromatography coupled with single quadrupole mass spectrometry (IC -MS) for a selective and sensitive determination of bromate in flour and flour products. The Thermo Scientific ™ ISQ™ EC Single Quadrupole Mass Spectrometer allows seamless integration of IC with MS, taking advantage of the strengths of both techniques. IC separation with eluent generation and suppressed conductivity detection provides chromatographic selectivity and analytes in the ionic form. Electrospray ionization (ESI) introduces the liquid IC stream (after suppression) as a fine spray into the MS source. Flour samples were extracted with high-purity water and subjected to a series of simple clean up steps before they were analyzed on the IC-MS system. We used a recently introduced Thermo Scientific™ Dionex™ IonPac™ AS31 column to separate bromate from matrix anions. The IonPac™ AS31 column is a high capacity column which allows large injection volumes, thus allowing the determination of low bromate concentrations. In this work we analyzed various samples including flour, burger buns, white bread, bread (baked using bromated flour), etc. The method showed good precision and accuracy with recovery of 90–110%. The limit of detection (LOD) and the limit of quantitation (LOQ) of bromate in the solution were 0.10 ppb and 0.34 ppb, expressed as H79BrO3- (m/z 127), respectively, which corresponded to 5 µg/kg and 17 µg/kg, respectively, in bread.

Selective and sensitive determination of bromate in bread by IC-MS

2019 Fall National Meeting

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