Direct determination of iron and selenium in bovine milk by graphite furnace atomic absorption spectrometry

Milk is a complex sample containing high contents of organic compounds and its analysis generally involves digestion procedures that can be affected by losses and contamination. In the work here described it was developed a procedure for determination of Fe and Se in bovine milk. Samples were diluted using a mixture of water-soluble tertiary amines (10% v/v CFA-C). The tertiary amines had a favorable effect on the action of the autosampler and consequently on repeatability. Using this strategy the direct analysis of milk without any digestion procedure by graphite furnace atomic absorption spectrometry is feasible. Pyrolytic graphite tubes were used and all measurements were based on peak area of transient signals with background signal correction based on Zeeman effect. Palladium was used as chemical modifier for Se. The pyrolysis and atomization temperatures were 1300 and 2300 °C for Fe and 1500 and 2400 °C for Se, respectively. The procedure was applied for 13 bovine milk samples from different sources. The quantification was based on the standard additions method. The lifetime of the graphite tube was 300 and 250 heating cycles for Fe and Se, respectively.