Photoinitiators are the key compounds in polymeric reactions. Under the light they decompose to free radicals, cations, or anions which are part of polymerization process. Photoinitiators are widely used in printing (UV-inks, packaging materials print, 3D print), medicine, synthesis of polymeric materials etc. Photoinitiators have many advantages such as low emissions of volatile organic compounds (important for environment), area and time control (important with production) and low energy consumption (economy reasons). Their impact on human health and degradation of products is a slow and hardly noticeable process at usual conditions, but it is cumulative and therefore it is important to know the content of these compounds.
In my master thesis I have focused on the determination of photoinitiators, 1-hydroxycyclohexyl phenyl ketone (1-HCHPK) and salts of triarylsulfonium hexafluoroantimonate (THS) in the samples of selected polymeric materials. Identification and quantification of photoinitiators was accomplished by using liquid chromatography with gradient elution. The diode array detector enabled the identification based on the UV spectra. On the basis of prepared calibration curves, I have determined the content of selected photoinitiators in the samples of polymeric materials. In addition, limit of detection and limit of quantification was determined in sample solutions as well as in the standard solution.
I have optimized the extraction of compounds 1-HCHPK and THS from the polymeric materials. I have examined the influence of particle size of sample and composition of extraction solvent on the extraction efficiency. For the extraction a mixture of 0.1°% TFA and ACN in ratio 7:3 was used. The prepared suspension of sample in extraction solvent was in the dryer at the temperature of 70 °C for 21 h. Solution was than filtered through 0.45 µm filter and injected into liquid chromatograph. The optimized method gave repeatable results. To summarize the obtained results, particle size does influence the efficiency of the extraction. If the particles are smaller, the efficiency of the extraction is higher. Meanwhile the composition of extraction solvent does not influence the efficiency of the extraction. Based on the results of analyses of real samples, it can be concluded that the samples are not homogeneous and that determined compounds degrade over time.
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