Repeatability is studied by calculating the relative standard deviation-RSD for a total of eleven determinations of the concentration of zinc (five 0.80 μg/mL zinc for repeatability and three 0.80 μg/mL zinc and 1.00 μg/mL zinc each for intermediate precision) performed under the same experimental conditions. The results of zinc determinations in the working standard solution with the relative standard deviation calculated are shown in Table 3 and Table 4. Intermediate precision includes the estimation of variations in analysis when a method is used within laboratories but on different days.