Levels of inorganic constituents in raw nuts and seeds on the Swedish market.

The levels of approximately 70 elements were determined in different culinary nuts (hazelnuts, walnuts, almonds, bitter almonds, pecans, cashews, Brazil nuts, pistachios, pine nuts, peanuts and coconuts) and seeds (pumpkin and sunflower) available on the Swedish market. The study was limited to raw, virtually unprocessed nuts and seeds (both shelled and unshelled) excluding mixed, roasted or salted products. In total, 44 products from different suppliers were analyzed, with the number of samples per nut/seed variety reflecting the availability of unprocessed products in retail outlets, varying from two for bitter almonds and pistachios to six for hazelnuts and walnuts. This selection includes samples from at least 11 different countries of origin. The optimized analytical procedure consists of microwave-assisted sample digestion using a HNO3/HF mixture, followed by multi-elemental analysis by double focusing, sector field inductively coupled plasma mass spectrometry. The analyses were accompanied by rigorous quality control measures including thorough control of potential sample contamination at all analytical stages, participation in inter-laboratory performance assessment schemes, and the analysis of certified reference materials of plant origin. Concentrations thus obtained were compared with data from product labels (where available), food composition tables and other relevant surveys, demonstrating, depending on the elements in question, close agreement as well as considerable differences.