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Determination of chromium in refined and unrefined sugars by oxygen plasma ashing flameless atomic absorption

The interest in possible submarginal deficiencies of trace elements that may occur as a consequence of changing nutritional practices has led to the collection and measurement of the chromium content of refined and unrefined sugars from various countries. Analyses were carried out by graphite furnace atomic absorption. Cr content which in the less refined sugars and in the molasses amounts to 160 and 270 mg/g drops to one-tenth of these values when sugar is refined. Cr in sugar, as in many biological sources, may occur in different chemical forms. The biological active form is most likely an organic complex whose chemical and analytical characteristics are poorly known. Erroneously low analytical results are obtained due to the loss of an organic Cr complex when sugar samples are introduced directly into the graphite furnace or ashed at 450oC prior to analysis: added inorganic Cr is not lost. More Cr is lost from unrefined sugar than from refined suggesting a decrease in content of the organic Cr during refinement. To avoid this loss of Cr, it is essential that the sugar samples be ashed at a low temperature, e.g. by the action of an activated oxygen plasma. It is likely that similar Cr analytical problems exist with other biological materials

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