Direct determination of arsenic, cadmium, cobalt, copper, chromium, lead, tin and zinc in white beet sugar using graphite furnace atomic absorption spectrophotometry

A quick and simple method for the direct determination of As, Cd, Co, Cu, Cr, Pb, Sn, and Zn in white sugar by Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS) is described. Because sample preparation is avoided, the analysis time and the risk of sample contamination are considerably decreased. Sucrose solutions are prepared by dissolving crystalline sucrose in 0.1% “suprapur” nitric acid. Except for Zn, where the dilution is 1.25%, the rest of metals are analyzed at a dilution of 10%. Palladium and ascorbic acid are used as the matrix modifier for all metals except for Zn which is analyzed without a matrix modifier. Air ashing is employed and quantification is accomplished by peak height measurements using standard additions calibration. The optimized furnace program permitted the direct determination of the elements at the mg/kg level. The method was validated by analyzing commercial white beet sugar samples and samples spiked with known quantities of the elements ranging from 10–80 mg/kg of dry sucrose, depending on the element considered. Recoveries ranged from 89% to 115%.

The procedure was applied to the determination of elements in commercial beet sugar samples and levels of metals below 5 mg/kg Cd, 8 mg/kg Co, 60 mg/kg Cu, 5 mg/kg Cr, 15 mg/kg Sn, 38 mg/kg Pb and 82 mg/kg Zn were found. Arsenic contents were always below the 22 mg/kg detection limit, as was to be expected.