Absolute quantitative electron microscopy of thin biological specimens by energy-dispersive x-ray microanalysis and densitometric mass determination

The method described is capable of measuring both the absolute mass and the mass fraction of elements is isolated thin biological specimens. To determine the elemental mass, characteristic x-rays emitted under electron irradiation are used, whereas the total mass of the specimen is found from electron scattering. Comparison with measurements on standards allows the calculation of the absolute elemental mass and elemental mass fraction values. The number of x-ray quanta per atom of a particular element, detected under strictly standardized procedural conditions, is given by a unit x-ray count value. Such values were determined for magnesium, phosphorus, sulfur and calcium using spray droplets as standard specimens.