For XRF substrate correction, how many locations must be scraped bare for readings?

The correct choice requires scraping bare two locations to ensure accurate readings in X-ray fluorescence (XRF) substrate correction. This practice is important because it provides a more reliable basis for analyzing the underlying substrate material that may affect the elemental composition readings obtained through XRF. By taking readings from two distinct locations, it allows for a better assessment of variability across the surface being tested and helps average out any inconsistencies or anomalies present in any single area.

When dealing with materials, especially in environmental assessments or quality control processes, variations can occur due to factors such as coatings, contamination, or localized differences. Scraping two locations offers a more comprehensive overview and increases the likelihood that the data gathered reflect the true properties of the substrate, rather than just anomalies caused by surface conditions or irregularities.

Choosing fewer than two locations would not provide sufficient data to validate the accuracy of the readings. In contrast, scraping three or four locations might be considered excessive for many standard assessments, where two valid measurements suffice to achieve reliable results without unnecessary complication.