In EDS measurements, the most important parameters which need to be optimized are:
          i) Sample tilt.
          ii) Working distance.
              Each instrument has its own character so that no two from the same or different manufacturer(s) are exactly the same, and thus you always need to search for the "perfect" X-ray working distance for each X-ray system. In many cases, you need to be aware that the quality of STEM images are not in the best condition when the X-ray count rate is maximized if EDS and STEM are not well coupled.
          iii) Sample preparation, and positioning in the microscope due to X-ray absorption consideration if the sample is structured.
          iv) Sample preparation, and positioning on the grid due to shadowing effect by the TEM grid if it is TEM sample.

The optimized parameters mentioned above would be where you get the maximum count rate.

One needs to use the more intense characteristic energy lines to obtain more accurate composition. For instance, for the Mo case shown in Figure 1248, the intense, primary L lines are normally selected in Mo EDS measurements.