Quantitative electron probe microanalysis of biological specimens-II. Determination of ϱX value of the analysed spot

A method for determining the ρ{variant}X value (density times thickness) of the analysed spot in a thin specimen when mounted on an aluminium support is described. An electron microprobe was modified so as to enable the measurement of the radiation which was generated within the aluminium support and transmitted through it. Several standard films with ρ{variant}X values ranging between 0.1 and 1.0mg cm^-2, made of aromatic polyamide organic matrix, and containing calcium and chlorine, were used for calibration. It was shown that the ρ{variant}X value of an analysed spot could be simply determined from the equation ρ{variant}X = 0.0064 (1 - R) E^1.68 where R is the ratio between intensity of radiation generated under the specimen and that generated in an exposed aluminium foil; and E the accelerating voltage in kV.