Metallic contamination of food during preparation and storage: development of methods and some preliminary results

A chemical procedure for studying trace metals leached from metallic cooking utensils and preserving cans used in the preparation and storage of food has been developed. The method consists in the destruction of the major part of organic matter with HNO3-vapour followed by a complete mineralization of residues with small amounts of HNO3 in Teflon bombs at 150-160 degrees C under a pressure of 3-12 kg/cm2, depending on the amount and composition of the samples. Subsequently, an ion-exchange step removes major components and concentrates the trace elements in a dilute HNO3-solution, suitable for analysis. The ion-exchange separation, which is performed with an automatic ion-exchange separator, is practically free from blank level problems, e.g., typically a mean of less than 2 per cent of the sample levels of the elements being determined. Preliminary results show that large amounts of aluminium are released from vessels to the water during boiling at the same pH-range which exist for most drinking water in Sweden.