Determination of trace elements in lichens by instrumental neutron activation analysis

Instrumental neutron activation analysis has been applied to analyze epiphytic specimens of the lichen Canoparmelia texana. Samples collected from the barks of the trees were previously cleaned, lyophilized and ground to be irradiated under a thermal neutron flux in the IEA-R1 nuclear reactor. Elements Al, As, Br, Ca, Cd, Cl, Co, Cr, Cs, Fe, Hf, K, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Mg, Mn, Na, Rb, Sb, Sc, Se, Th, Ti, U, V, and Zn were determined quantitatively by using short and long irradiations. Comparisons were made between the results for washed and unwashed samples as well as those collected in two different years, from individual palm trees and also from different sites of Sao Paulo State. The precision and the accuracy of the method were evaluated by analyzing NIST 1572a Citrus Leaves, IAEA 336 Lichen and USGS W-1 Rock reference materials. (author)