Comparative elemental analyses of a standard plant material

Abstract

Results are reported by 29 laboratories for the analytical determination of 40 elements in standard kale powder. Consistent results were obtained by more than one laboratory for Au, B, Ba, Br, Ca, Cl, Co, Cr, Fe, Ga, I, Mn, Mo, N, P, Rb, S, Sc and W. Small differences between results obtained by different techniques were found for Cu, K, Mg, Na, P, Se, Sr and Zn. Of these, the most significant were: that flame photometry gave high results for Na; that activation analysis without chemical separation was unreliable for determining K and Mg; and that atomic-absorption spectrometry gave high results for Cu and Sr. Gross discrepancies were found in the results reported for Al, As, Hg, Ni and Ti. Similar anomalies have been reported in analyses of mammalian blood. Where possible, the precisions of different analytical techniques were compared.