Chlorites and chlorates are inorganic ions that appear in water samples. These ionic species are byproducts of disinfection when chlorine dioxide is used. Since they have toxic effects, it is necessary to identify them in a timely manner. Ion chromatography is suitable for the analysis of chlorites and chlorates due to its specificity, automation, high sensitivity, precision, and repeatability. Additionally, sample preparation for ion chromatography is simple and fast, and only small quantities of the sample are required for analysis. Another advantage of ion chromatography is that it enables the simultaneous detection of different anions and cations in samples. This thesis conducted a verification of an existing method for the determination of chlorites and chlorates in water samples by ion chromatography. The validation parameters examined were: linearity, repeatability, accuracy, detection limit, quantification limit, and concentration range. All obtained results met the prescribed acceptance criteria (correlation coefficient r g 0.995, quantification limit 0.05 mg/L, repeatability RSD f 10 %, and recovery of 100 ±10 %). Eight sources of measurement uncertainty were selected for analysis: standard purity, micropipette 10-100 μL, micropipette 100-1000 μL, 10 mL volumetric flask, calibration curve, measurement repeatability, recovery and reproducibility of sample preparation. Among all the examined sources of measurement uncertainty, for both analytes, calibration curve had the greatest impact. Combined and expanded measurement uncertainties were also calculated..