Determination of essential and potentially toxic trace elements in honey by inductively coupled plasma-based techniques.

The mandate assigned by the European Union to the Community Reference Laboratory for residues at the Istituto Superiore di Sanità covers, among other things, the assessment of trace elements in living animals as well as their products. To better protect the health of the consumer, this task aims in particular at harmonizing the procedures in use at the National Reference Laboratories (NRLs) for residues of the Member States for such determinations as well as at developing new approaches wherever the need arises. In this context an investigation was undertaken to appraise the average levels of a number of key elements in several types of honey with special regard to the influence of the various processing steps. Instrumental methods of election for the analysis of this matrix turned out to be inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) depending on the actual concentrations of the elements of interest. Dissolution of the samples for suitable presentation to the analytical systems could be easily achieved by gentle heating at ca. 50 degrees C, sonication and addition of high-purity water. The ranges ascertained are as follows (in ng g(-1)): As, <0.50-0.70; Cd, <0.50-0.74; Cr, 1.03-3.93; Cu, 144-216; Fe, 191-651; Mn, 223-580; Ni, 17-49; Pb, 3.20-186; Pt, <0.50; Sn, <4-27; V, 1.22-1.94; and Zn, 565-1144. As a rule, concentrations of elements in honey from different beehives were similar. A few exceptions were noted for As, Cu, Fe, Ni and Zn. On the other hand, although data obtained with different analytical approaches for the same types of honey and beehive were generally in good agreement, yet some inconsistencies occurred, as in the case of Cu in freshly collected, extracted and ripened honey, Ni in extracted honey and Fe in ripened honey. These could not be traced back to specific procedural facts; rather, they should be ascribed to the inherent heterogeneity of the raw material. The experience gained with this exploratory study will be exploited to set up wider surveys and to plan the preparation of a new certified reference material in a matrix of honey to the benefit of NRLs for residues.