Evaluation of sample preparation methods for cereal digestion for subsequent As, Cd, Hg and Pb determination by AAS-based techniques.

Sample preparation methodsforcereal digestion were evaluated for the first time for subsequent As, Cd, Hg, and Pb determination by atomic absorption spectroscopy techniques. Microwave-assisted digestion (MW-AD) under high and medium pressure and microwave-induced combustion (MIC) were evaluated. The use of MIC made it possible to digest 700 mg of samples, and agreements of 97, 96, 100 and 92% were obtained for As, Cd, Hg and Pb, respectively, when 7 mol L HNO was used as the absorbing solution. It was not necessary to dilute the digests obtained to avoid interferences in the quantification of As, Cd, Hg, and Pb. Although high pressure MW-AD was efficient for cereal digestion, interferences were observed on analyte determination. Limits of quantification obtained by MIC were 0.034 (As), 0.015 (Cd), 0.021 (Hg) and 0.105 (Pb) μg g, which are suitable to attain the maximum levels recommended by international agencies in cereal samples.