Biological Reference Materials for Trace Element Analysis: What is New?

Abstract

In biomedical trace element research, reference materials are a relatively recent development: indeed, Bowen's Kale Powder became available only in the middle of the 1960s, NBS Orchard Leaves (SRM 1571) and NBS Bovine Liver (SRM 1577) in the beginning of the 1970s. In general, when compared to a number of real samples submitted to laboratories for elemental analyses, these reference materials have high or relatively high trace element concentrations. This is probably best illustrated when the levels expected in human blood plasma or serum (matrices which are frequently analyzed both because of their established biomedical importance and their ready availability) are considered. For example, for chromium and manganese, figures are as follows-370 and 14,950 ng/g (in Bowen's Kale Powder), 88 and 10,300 ng/g (in NBS Bovine Liver), and 1.5 and 5.5 ng/g dry weight (in human blood plasma or serum). So, although the above-mentioned, first generation biological reference materials rendered excellent services as a means to check the accuracy and precision of analytical techniques, large numbers of investigators were still largely left to their own devices. Some reference materials are specifically aimed at researchers working on human blood plasma or serum, e.g., NBS Human Serum (SRM 909), Nycomed's Human Serum (STE 105), and National Institute for Environmental Studies' (NIES) (Japan) Freeze-Dried Human Serum. In all three cases, however, it is obvious that the original levels of several elements must have been drastically distorted during the collection and preparation of the