In this bachelor's thesis, I investigated the influence of spectral interferences on the absorption spectrum of macrocomponents in an acidic medium using molecular absorption spectrometry in ultraviolet range. Trisodium citrate was used as the model system. Particular attention was devoted to changes in spectral shape in the wavelength range between 200 and 230 nm, where literature reports the possible influence of additional components present in citrate blood collection tubes. The absorption spectra of citrate and various potential interfering components were analyzed, including nitrate, nitrite, oxalate, formate, acetate, bromide and chloride. The spectral properties of individual components were compared with the spectrum of trisodium citrate, and their potential influence on the shape of the absorption band was evaluated. Measurements were performed in a 126 mmol/L HCl medium, and the influence of the medium itself on spectral shape was also investigated. To improve the differentiation between individual components, first-derivative absorption spectra were analyzed in addition to the zero-order spectra. Comparison of derivative spectra enabled a more precise evaluation of spectral shape changes, particularly differences in the positions of extrema, zero-crossings, and curve slopes. The results showed that some interfering components primarily caused an increase in absorbance at the citrate absorption maximum. In the final part of the study, absorption spectra of citrate solutions prepared from different blood collection tubes were also analyzed and compared with the spectrum of reference citrate. Differential spectroscopy proved to be a useful approach for detecting spectral interferences and evaluating changes in the shape of spectra in complex systems.
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