In the diploma work, we evaluated the measurement uncertainty of selected volumetric instruments and the factors that influence each type of dilution. We presented the differences between the types of dilution an explained the process of calculating the combined measurement uncertainty. In the experimental part, we determined the repeatability of filling volumetric instruments (flasks, volumetric pipettes, and piston pipettes) by weighing. Based on the experimental results, we calculated the combined measurement uncertainties of the dilution factor for both cases of dilution. We found that the value of measurement uncertainty of the dilution factor when diluting solution to volume for an individual volumetric flask decreases with increasing volume of the pipette, while when diluting solution with volume it increases with increasing volume of the pipette addition. The greatest influence on the measurement uncertainty was due to repeatability of filling, where there were also minor deviations. We must be careful to fill as repeatably as possible, use clean and uncontaminated instruments and work under constant conditions (temperature, pressure) to obtain results in a certain range, as all these components affect the measurement uncertainty.
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