Fig. 1.
Fe, Cu, and Zn standards. Top panel: Congealed solutions of Fe-III-, Cu-II-, and Zn-II-mesoporphyrins in gelatin capsules. The highest concentrations are present in ① of each standard. After dilution, the concentrations range, in micrograms per milliliter, from 620 to 19.375 for Fe; 86 to 2.688 for Cu; and 74 to 3.125 for Zn. Middle panel: Matching XRF maps of the standards shown in the top panel. Pseudocolors indicate the declining concentration from maximum (white) to red, green, light blue, and dark blue. Bottom panel: Regression analysis of Fe, Cu, and Zn. Ten point-measurements were made of each standard concentration and averaged. The mean values were reduced by background XRF that was obtained by sampling the block outside the capsules. The goodness of fit is given by R 2 values. Bars in top and middle panels represent 5 mm