EVALUATION OF SEVERAL COMMON STANDARDS FOR THE X-RAY-MICROANALYSIS OFTHIN BIOLOGICAL SPECIMENS

The question of the best type of standard to use for X-ray microanalys is of thin biological specimens remains unanswered. Standards embedded in an organic matrix have the advantage that they resemble biological specimens, but their composition is generally not known exactly. We c ompared several standards and, surprisingly, inorganic binary salts sp rayed onto a supporting film were the most suitable: they corresponded closely with several other methods using organic matrices; they were easily produced: and their composition is known. Glutaraldehyde-urea a minoplastic resin thin sections and thin films containing dissolved sa lts were problematic. The composition of the polymer appears to be var iable, and the thin films did not correspond with any other standard t ested. Chelex100 bio-standard beads and flakes loaded with accurately determined concentrations of ions, embedded in epoxy resin and thin se ctioned, tended to correspond to the results obtained with the binary salts. However, the results from some bio-standards were inexplicably aberrant. An epoxy resin standard was used for bromine, and was found to agree closely with the binary standards.