Abstract
Mineral oil hydrocarbons (MOHs) are complex mixtures of saturated (MOSH) and aromatic (MOAH) compounds derived from petroleum. In food-related applications, their migration from packaging materials may result in food contamination, which may cause potential adverse effects to humans, including bioaccumulation and genotoxicity, as well as carcinogenic effects. On the other hand, they tend to persist in the environment where they have the same effect, so it is important to develop a method that can preconcentrate them properly and separate the two fractions from each other. MOSH and MOAH have different health effects, which justify the need to separate and quantify these classes of compounds. Current analytical methods rely on instrumental techniques such as high-performance liquid chromatography (HPLC) and liquid chromatography (LC). They also rely on sample preparation methods such as solid phase extraction (SPE). Although these techniques are reliable, they are often expensive and solvent intensive. Specifically, the SPE is time-consuming and prone to low recoveries. These limitations create barriers for routine monitoring, particularly in developing countries such as South Africa, where regulations for monitoring MOH contamination are absent.
Argentation chromatography is often employed for the selective extraction of aromatic hydrocarbons, where silica gel is impregnated with silver (Ag) ions, which can selectively interact with pi-bonds. The alternative is SPE where the silica sorbent is impregnated with silver ions. This study proposes the development of 3D printed Ag/polymer nanocomposite-based sorbents for SPE to replace traditional sorbents that are time-consuming to prepare. The nanocomposite material was prepared in-house by combining melt blending and in situ reduction of Ag+ within the polymer matrix based on the method described by Vidakis et al., with modifications. The sorbent was successfully 3D printed using fused deposition modelling (FDM), and the resulting nanocomposite material was characterised using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and thermogravimetric analysis (TGA). The 3D printed fabricated sorbents were tested as alternatives to traditional SPE sorbents.
The initial proof-of-concept testing with model MOH compounds revealed challenges in extraction efficiency as these compounds were not effectively separated from each other. Therefore, the scope of analytes was expanded to include polyaromatic hydrocarbons (PAHs). Performance evaluation using mineral oil marker compounds and EPA priority PAHs revealed fundamental limitations in the current approach. MOH fractionation showed approximately 70% immediate elution with no MOSH/MOAH selectivity. PAH extraction from aqueous matrices yielded uniformly low recoveries across all nine sorbents. Both PP and nylon exhibited non-selective retention behaviour, with PP performing marginally better than nylon, which is attributed to its lower polarity. This study aimed to develop and evaluate 3D-printed sorbent technology for the extraction of aromatic hydrocarbons from environmental and food matrices using SPE. The work highlights both the potential and the current limitations of this emerging approach. Although the materials did not achieve the required selectivity or recovery, the study establishes a foundation for future optimisation of 3D‑printed sorbent design as a cost‑effective analytical tool for MOH and PAH monitoring, particularly in developing countries.