BIOLOGICAL APPLICATIONS OF A COMPUTER CONTROLLED ANALYTICAL ELECTRON MICROSCOPE

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Experimental measurements have been made on the relative sensitivities of parallel EELS and EDXS for a series of elements commonly encountered in biological microanalysis. The results were compared with theoretically derived estimates based on scattering cross sections and collection efficiencies. The EELS and EDXS data were collected simultaneously on the Hitachi H700H analytical electron microscope. Energy loss spectra were collected in the second-difference mode to eliminate channel-to-channel gain variations. Multiple least squares fitting of reference spectra was used to quantitate the data. It was shown that EELS can detect not only the light elements with high sensitivity through the K-shell excitation but can also detect elements such as calcium, iron and phosphorus through the L-shell excitation. Sensitivity for calcium is shown to be about three times higher for EELS than for EDXS provided the sample is sufficiently thin. Sensitivities for iron are about the - same for the two spectroscopies. Detection limits for phosphorus are about six times lower for EELS than for EDXS.