THE DETERMINATION OF THE FLOUR IMPROVER POTASSIUM BROMATE IN BREAD BYGAS-CHROMATOGRAPHIC AND ICP-MS METHODS

The development and application of two methods for determining bromate in bread are described. A gas chromatographic (GC) method which relie d on the formation of a volatile derivative of bromate gave a detectio n limit of 12 mug/kg. Duplicate analyses agreed well but recovery from breads spiked with bromate were low and averaged 30% for brown bread and 42% for white bread. Further studies indicated that this was cause d by the derivatization reaction being suppressed by components of the sample and reagents used in their preparation. After taking both thes e factors into account, a recovery of 80% could be achieved. The GC me thod was used to carry out a survey of retail bread samples in 1989. B romate was found in all six unwrapped breads analysed (median 35 mug/k g, range 17-317 mug/kg), whilst for 22 wrapped breads, seven were foun d to contain bromate (median < 12 mug/kg, range < 12-238 mug/kg). A se cond method of analysis employing inductively coupled plasma-mass spec trometry (ICP-MS) was developed which provided independent confirmatio n of the presence of bromate in these retail samples. The method gave a mean recovery of 71% from five spiked samples and a detection limit of 20 mug/kg. The GC and ICP-MS methods were compared by performing re plicate analyses of a bread sample prepared with bromate-treated flour . Quantitative agreement the two techniques was good. The precision of the ICP-MS technique (CV 12%) proved better than that found for the G C method (CV 18%). The Potassium Bromate (Prohibition as a Flour Impro ver) Regulation 1990 came into force on 1 April 1990 (Statutory Instru ment 1990 Number 399). A second survey of those brands of bread which had previously been found to contain bromate was carried out in 1992. All samples contained less than the detection limit of 12 mug potassiu m bromate/kg flour.