Elemental analysis using differential absorption techniques

X-ray differential absorption microanalysis is presented as a technique for trace element analysis of hydrated biological specimens of about 0.1–5 μm thickness. For the study of the light elements (Z?20), the absorption technique minimizes the radiation dose and, thus, damage to such specimens when compared with X-ray fluorescence. A Scanning Transmission X-ray Microscope (SXTM) is described, which has been used to map the concentration of calcium in bone with better than 300 nm spatial resolution and a sensitivity to 5% calcium by weight. Future plans are briefly discussed that offer the hope of achieving 0.1% trace element sensitivity and 75 nm spatial resolution.