Validation of mineralisation procedures for the determination of selenium, zinc, iron and copper in chicken meat and feed samples by ICP-AES and ICP-MS

Mineralisation procedures for determining Fe, Zn, Cu and Se in chicken meat and feed samples were studied. We employed three different sample preparation procedures to determine these elements by ICP-AES and ICP-MS. An open vessel wet mineralisation procedure was used for chicken meat analysis. Here, in the case of the trace elements Cu and Se, it was necessary to concentrate and reduce the acid matrix effects so samples were heated to dryness. However, this procedure causes Se volatilisation losses leading to low recoveries and high variability. Therefore, a closed vessel microwave mineralisation procedure was developed for chicken meat samples. The results obtained using this procedure presented a much lower variability (2.5, 2.0 and 3.1% of RSD for Zn, Fe and Se, respectively) and were consistent with the certified values for the reference material being assessed. Cu content, despite presenting a relatively high variability ( RSD = 11%) also agreed with the certified value for the reference material. Recoveries in spiked chicken meat were 103 - 105% for Zn, 107 - 108% for Fe, 97 - 100% for Se and 89 - 94% for Cu. However, when this procedure was used with feeds, some mineralised samples presented siliceous particles which led to a lower recovery of Zn compared with that recorded when using another microwave mineralisation procedure in which these particles had been dissolved with hydrofluoric acid. This alternative mineralisation procedure for feeds was validated by assessing the precision, recovery and sensitivity when determining each element.