Structural Group Composition Analysis of Some Plasticizers and Their Plant-Based Equivalents Using High-Performance Liquid Chromatography, NMR Spectroscopy, and NMR Relaxometry

The structural-group characteristics of the Norman 346 and 132 plasticizers as well as their plant-based analogies, Phytonorman 212 and 213, have been studied using high-performance liquid chromatography, high-resolution NMR spectroscopy, and NMR relaxometry. All three methods indicated that the Phytonorman 213 sample differed significantly from both Phytonorman 212 and Norman 132 (mineral oil), which was claimed to resemble by the manufacturer. According to the data of NMR relaxometry, the average transverse relaxation time was 121.3 ms, i.e. exceeded that of the Phytonorman 212 and Norman 132 almost 3-fold thus indicating a significantly lower viscosity of the Phytonorman 213 sample. HPLC results also showed a significantly lower content of mono-aromatics and a significantly higher content of bi-aromatics in Phytonorman 213. Furthermore, NMR spectroscopy data for Phytonorman 213 revealed a 12% decrease in the concentration of secondary and quaternary hydrocarbon groups, along with the 8.6% increase in the concentration of tertiary hydrocarbon groups compared to its non-plant analogue. The results demonstrated that modern analytical methods used to assess the structural group composition generally provide comparable results. However, it is evident that HPLC and NMR relaxometry are the most suitable techniques for the routine, day-to-day analysis in quality control laboratories due to their relative affordability and simplicity of use.