CPS mapping and normalization of a vitamin caplet cross-section

Instruments used

EDAX^® Octane Elite silicon drift detector and EDAX APEX™ software for EDS

Background

Flat and smooth surfaces are preferred for energy dispersive x-ray spectroscopy (EDS) mapping but are often hard to produce on real world materials. For vitamins and dietary supplements, the ingredients in fine-powder form are often mixed and then compressed into caplets, sometimes with a coating. EDS mapping of a caplet cross-section is a quick and easy approach to investigate the components’ spatial distribution in the caplet. However, these compressed powders usually form a rough sample surface, and some aggregates may fall off to leave relatively large craters. While a caplet cross-section is being x-ray mapped point-by-point, the x-ray count rate changes not only due to variations in atomic number and density but also due to topography and surface anomalies, which challenge the accurate representation of the elemental and phase distributions in the sample. Previously, it has been left to the user to decide and interpret the effects of these conditions on the sample analysis. The counts per second (CPS) map feature in APEX now assists with these often difficult to understand interpretations. The CPS map provides a visual representation of the x-ray count rate at every pixel in the dataset. It is a quick and easy check of the variations in count rate across the sampling area. The artifacts produced by topography and surface anomalies can be compensated for by applying a CPS normalization.