This final thesis deals primarily with the comparison of two calibration approaches. It determines the degree of mutual agreement and tries to answer the reasons of their deviations. This agreement was measured by the LDA method. It was found that the calibration approach based on the reference framework of values of the previous bachelor thesis differs systematically from the calibration using calibration equations obtained from certified laboratories by -2 %. The causes of this deviation were investigated using LDA and PIV. Although a significant number of measurements were performed, all tested hypotheses were refuted and therefore it was not possible to determine their cause.