Elemental analysis of individual rat blood platelets by electron probe X-ray microanalysis using a direct quantification method.

The elemental content of individual rat blood platelets and their dense granules was determined by electron probe X-ray microanalysis using a direct quantification method with microdroplets as standards. The quantification procedure was a modification of the 'direct mass' method involving a correction for differences in electron beam intensity in the analysis of standards and specimens. Whole air-dried platelets had a mean magnesium content of 12 X 10(-8) nmol (SE = 1 X 10(-8) nmol, n = 68) and a mean calcium content of 3.2 X 10(-8) nmol (SE = 0.3 X 10(-8) nmol, n = 68). A good correlation was found between the magnesium content and the phosphorus content of the dense granules of the platelets (r = 0.95). There was also good correlation (r = 0.77) between the number of dense granules per platelet and the magnesium content of the platelets.