Development of trace element analysis by charged-particle induced X-ray fluorescence spectrometry is reviewed, with emphasis on specimen preparation and calibration. A case is presented for the use of wet-digested specimens together with internal standards. Data on ionization cross-sections, fluorescence yields, and detector efficiencies, quantities necessary for measurements relative to internal standards, are reviewed. Experiments are described which test specimen sampling procedures, target integrity, consistency among different standards, and the accuracy and reproducibility of analytical results. Analyses of wines, biomedical specimens, and NBS orchard leaves are described. For fluids, detection limits are 0.01 to 0.1 ppm while, for wetdigested tissues, the limits relative to the original material are 0.1 to 1 ppm.The use of charged-particle beams from accelerators as a means of excitation in energy-dispersive X-ray fluorescence spectrometric analysis has received considerable attention in the past four years. Widespread interest in this

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X-ray fluorescence induced by charged particles has been employed in trace element analysis of both animal and human blood, tissue and bone samples. Preparation techniques included microtome slicing and wet digestion in nitric acid, internal chemical standards being used in the latter case.Most of the specimens arose from a study of interactions between the toxic elements lead and zinc in growing foals; this was motivated by reports of sickness and death in foals raised near lead-zinc smelters. The cause of toxicity in animals from environmental pollution is often attributed to Single factors, whereas in reality interactions among many factors, including a variety of toxic and nutrient trace elements, should be considered.A variety of spectra are presented and elemental concentrations derived. Agreement between the X-ray data and atomic absorption spectrophotometry is encouraging. The results demonstrate the potential of particle-excited X-ray fluorescenee as a broad-range analytical technique for the study of trace element interactions.