Plant analysis of trace elements by X‐Ray‐

Abstract

Energy dispersive X‐ray fluorescence (EDXRF) has been shown to be an effective technique for multielement analyses of plant tissues. Elements can be assayed above the atomic number of Na (11) including S, Cl, Br, and trace elements, except B. Once parameters and programs critical for quantitative analyses have been developed, analysis is relatively simple. Overall optimal pellet weights of 500 mg (32 mm diameter) and 100 mg (13 diameter) were chosen. It was found that weights could vary ± 25% without significant change in intensities. Samples ground to 1 mm, 20‐mesh, and 80‐mesh did not show significant intensity differences. When 1 g of boric acid was used to back pellets, intensities for light elements (Mg, Al, Si, P, S) were increased, but for higher atomic number elements intensities decreased from 60% to less than 20% those of non‐backed pellets. Minimum detection limits (MDL) for various elements were (in ug/g 135 Mg, 32 Al, 28 Si, 25 P, 19 S, 9.3 Cl, 40 K, 30 Ca, 1.9 Mn, 1.4 Fe, 1.1 Cu, 1.0 Zn, 3 Mo, 2.3 Cr, 1.2 Ni, 1.2 Pb, 1 As, 1.5 Sr, 0.8 Br, and 0.5 Se. MDL values for Cd, Co, Rb, and Ba were near 9, 2.0, 2.0, and 0.5 respectively. Except for Mo, the MDL values for elements essential to plant growth were below concentrations usually found in normal or deficient tissue. MDL values for toxic mid‐Z elements could be determined in plants grown in media with relatively low levels of the elements. Operational parameters currently in use are also given.