Avoidance of contamination in element analysis of serum samples.

The selection of sampling needles and plastic material used for the storage of serum samples were studied. Sampling needles and plastic material were analyzed by neutron activation analysis. Leaching of elements from containers by acids and EDTA-solution was also followed. Also the long-term storage of serum samples for element analysis was investigated. Zn, Cu and Se concentration of serum was followed over the course of four years. The selection of sampling needles, as well as all plasticware which comes into contact with the serum, should be based on the knowledge of possible removal of elements from materials into the sample. Storage of serum samples at -18 degrees C does not change the copper, zinc or selenium concentration over the course of 4 years despite repeated melting and refreezing of the samples.