Analytical issues in nutritional chromium research

In most readily accessible biological samples from humans, like blood, serum/plasma, urine, etc, the levels of chromium (Cr) are less than 1 ng/g, and in many cases closer to 0.1 ng/g. Only 3 analytical techniques have the required sensitivity to make measurements at these levels, namely, neutron activation analysis (NAA), mass spectrometry (MS), and graphite furnace atomic absorption spectrometry (GFAAS). The first 2 are not widely available, and the third is the one most susceptible to interferences from the sample matrix. At the sub‐parts‐per‐billion level, collecting samples without contaminating them and generating sufficiently low analytical and reagent blanks become extremely important and difficult. For other determinations of Cr, eg, in diet components, foods and tissues, where the levels are often well above the ng/g level, the required sensitivity is less of a limitation, but contamination problems remain, and factors like sample processing and homogeneity become more important. Problems and precautions in Cr determinations are discussed, and means of accuracy verification are presented. A novel use of stable isotopes of Cr in an accurate, non‐radioactive method of measuring blood volume is described, as well as a discussion of the future of Cr determinations using inductively‐coupled plasma mass spectrometry. J. Trace Elem. Exp. Med. 12:99–109, 1999. Published 1999 Wiley‐Liss, Inc.