Estimation of phosphorus and sulphur contents in nuclear constituents by means of image-EELS analysis using ribosomes as internal standards

A quantitative study by means of electron energy-loss spectroscopic imaging (image-EELS) is performed on a biological specimen, using ribosomes as internal standard. Phosphorus and sulphur are studied; it is shown in the case of phosphorus analysis that results obtained are in agreement with a previous study using a different energy filtering microscope. In most biological specimens, atoms of sulphur may be present in the vicinity of phosphorus atoms; in such cases the signal obtained from sulphur will overlap with the continuum coming from the phosphorus signal, thus making the element-specific maps of sulphur superimposed on a background signal coming from phosphorus. In this work a method is suggested of separating the phosphorus contribution to the sulphur signal, using a reference spectrum from gallium phosphide. (C) 1999 Elsevier Science Ltd.