Abstract
Proton induced X-ray analysis of biological material in air is discussed. The microbeam system of magnetic quadrupoles which has been developed by Cookson and Pilling (see J. Radioanal. Chem., vol.12, p.39, 1972), for a 3 MeV accelerator, provides proton, deuteron or alpha beams focused to a spot of diameter less than 4 mu m. The beam emerges into air through a 7.5 mu m kapton foil, and in order to preserve positional resolution the specimens are mounted directly on the outside of the beam exit foil.