In the thesis, the spectral properties of five buffer solutions prepared in different buffer ratios which influenced the changes in the pH of the solutions were investigated by molecular absorption spectrometry. The analysed buffer solutions were phthalate with NaOH, citrate with HCl, citrate in combination with phthalate and HEPES, and HEPES in combination with citrate. The results showed that the buffering behaviour of phthalate with NaOH and citrate with HCl is less complex and that the change in pH is more significant compared to the other prepared solutions. In these cases, the pH change could be described by the pKa values of the protolysis for phthalate and citrate, respectively. In contrast, for the other solutions we had to take into account the pKa values of the added substance, which makes it somewhat more difficult to interpret the exact behaviour of the buffer.
When evaluating the spectral properties, we found that trisodium citrate, potassium hydrogen phthalate and HEPES absorb light in the UV range, with characteristic peaks that depend on their intramolecular electronic transitions. We discovered that phthalate absorbs the light the most intensively, while HEPES absorbs the least. The solvent Mili-Q water was found to be a very important factor influencing the spectra of the citrate and HEPES buffer solutions. For the diluted solutions, a shift of the absorption peaks towards shorter wavelengths, outside the measurement range, was observed. The importance of understanding the interactions of buffer systems and their spectral properties is crucial for the appropriate selection of buffers in chemical applications.
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