Quantitative electron probe x-ray microanalysis and densitometric mass determination of individual rat blood platelets.

An improved method for quantitative electron probe X-ray microanalysis of thin biological specimens, introduced recently, has been applied to the elemental analysis of rat blood platelets. The method uses the X-ray signal to quantify the elemental content of an object and electron scattering to determine the total dry mass of the object. Along with the dry mass distribution, data were obtained on the content and mass fraction of calcium, magnesium, and sulfur in 31 individual platelets. The mean platelet dry mass was found to be 985 fg. The mean Ca, Mg, and S contents were 1.80, 3.41, and 18.3 fg, with mean dry mass fractions of 0.195, 0.396, and 1.96%, respectively. Furthermore, these elements appear to be unevenly distributed among the platelet population.