Selected data for appropriate reference materials

Examples for reference materials useful for instrument calibration, method validation and development in the field of human materials for which certified or other kinds of concentration values are reported for the 13 trace elements considered in this book (Al, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Se, Tl, V and Zn) are given in Table 3. The data are taken from the survey prepared by Cortes Toro et al. (1990) and from other sources (BCR, 1992, Trahey, 1992, Chai Chifang, 1993) which the reader should consult for further details. Most of the columns are self explanatory. Column T contains a code (C = certified, N = noncertified or information value) for the type of reference value specified by the issuing authority. The uncertainty in the concentration value is expressed as a percentage error, but the meaning of this may differ somewhat from one material to another. In most cases it expresses the 95% confidence interval of the mean, but in a few other cases a tolerance interval, or some other definition (sometimes unspecified), may have been used by the producer. 

These data are presented in a way that is intended to help the user select a reference material that matches as closely as possible (i.e. with respect to matrix type and concentration of the element of interest) the real samples that are to be analyzed. 

It will be apparent from these data that, of the elements considered in this book, there is a serious lack of suitable reference materials for aluminium, vanadium and thallium. In addition, the uncertainties in the recommended concentrations are generally excessively large for all the elements considered in this book, except possibly copper, manganese and zinc. 

APPROPRIATE BIOLOGICAL REFERENCE MATERIALS USEFUL FOR INSTRUMENT CALIBRATION, METHOD VALIDATION AND DEVELOPMENT FOR HUMAN MATERIALS AND THE 13 ELEMENTS TREATED IN THIS BOOK 

The materials are listed in descending order of the elemental concentration the latter is expressed on a dry weight basis unless otherwise noted by an asterix in column T (see text for further explanations) 

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