When conducting research on hemostasis and coagulation, it is crucial that the concentration of anticoagulant in the blood collection tubes is appropriate. Any deviations can lead to errors in the results, which affect the interpretation of the blood count and further diagnosis. For determination of citrate concentration, we chose to use spectrometry because it is a simple, fast, relatively inexpensive technique that does not require preliminary steps. The problem with using spectrometry arises when we are dealing with more complex samples, when interferences are present and when the spectra of two components in the sample overlap. Previous studies have already addressed the issue of determining the anticoagulant sodium citrate in blood collection tubes and confirmed the presence of impurities. To solve the problem of citrate determination in the presence of possible impurities, we focused on new methods proposed in the literature, which are based on measuring two wavelengths and enable direct spectrometric determination of the components of the mixture despite the overlapping spectra. In the master's thesis, we successfully confirmed the applicability of the selected methods (dual wavelength method and dual wavelength resolution technique) on a model of the binary mixture sodium citrate-potassium hydrogen phthalate for direct spectrometric determination of citrate in the mixture in the presence of impurity and without prior separation. The methods were also applied to a real sample, represented by vacuum blood collection tubes. We were able to show that the concentration of the anticoagulant citrate in the blood collection tubes deviates from the concentration specified by the tube manufacturer. We also confirmed the presence of an interfering substance in the blood collection tubes, in addition to citrate, which absorbs in the ultraviolet range, and we excluded oxalate and phthalates, except for one sample of blood collection tubes, where the presence of phthalates is still suspected.
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