X-ray fluorescence microanalysis of thin biological specimens

An X-ray fluorescence unit has been designed for the microanalysis of thin biological specimens. Excitation is by means of a microfocus X-ray tube with transmission anode, and the X-ray spectroscopy is based on a Si(Li) detector. Tests show that the unit in its present form can measure amounts of potassium down to approximately 10 pg and potassium mass fractions down to approximately 30 ppm. Quantitative analysis is based on a normalization of the fluorescence signal against the measured intensity of scattered radiation.