Water quality control
Ozone is widely applied in drinking water processing
as a disinfectant and for the oxidation of organic micropollutants.
Spring water always contains some bromide. As a by-product
of bromide oxidation in the water disinfection process,
bromate ions are formed. Due to the potentially carcinogenic
nature of bromate, bromate levels in drinking and mineral
water have to be monitored.
The German regulations concerning drinking water prescribe
a temporary limit of 25 µg/L, other countries
already prescribe lower limits. The processing of mineral
waters suffers from similar problems. Here, the pertinent
regulations in Germany, dating from 1st July 2004, prescribe
a limit of 3 µg/L.
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Bromate analysis by Ion Chromatography
The IC/MS method yields the lowest detection limit,
the second best is ion chromatography followed by post-column
derivatization with iodide (in a post-column
reactor = PCR) followed in turn by UV detection.
The analysis can be reliably and accurately performed
with Metrohm's economical 844
Compact UV/VIS ion chromatograph (IC), which optionally
contains a built-in PCR.
The analysis is based on the Environmental
Protection Agency EPA method 326. In this post-column
derivatization method, bromate – aided by the
catalytic effect of ammonium molybdate – oxidizes
iodide to tri-iodide in an acidic medium. The tri-iodide
absorption is monitored at 352 nm and allows for the
calculation of the bromate concentration (so-called
indirect detection technique). As bromate is essentially
needed for the oxidation of iodide, the method described
here is limited to the determination of bromate; any
additional water constituents have to be determined
separately. As a column with a very high capacity is
used, the injected volume can be increased to 1 mL.
This results in a significant increase of the sensitivity
and allows to determine bromate in the medium ppt range.
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Food
Analysis 
