General Description

2-Isopropylthioxanthone, a widely used photoinitiator, is essential in UV curing technology for coatings, inks, and adhesives. Its photochemical reaction under UV light generates free radicals, initiating rapid polymerization for efficient curing. Additionally, it facilitates the quick and controlled polymerization of dental restoratives and is crucial in the manufacturing of optical fibers and electronic devices. However, caution is warranted as it can induce cytotoxicity when combined with certain chemicals, emphasizing the need for careful handling in occupational settings. Moreover, a sensitive detection method using HPLC/MS/MS has been developed to ensure the safety and quality of milk products by identifying potential contamination of 2-Isopropylthioxanthone.

Figure 1. 2-Isopropylthioxanthone

Applications

2-Isopropylthioxanthone is a photoinitiator commonly used in the field of polymer chemistry and UV curing technology. Its unique properties and applications make it an essential component in various industries. One of the primary applications of 2-Isopropylthioxanthone is in the UV curing of coatings, inks, and adhesives. When exposed to UV light, 2-Isopropylthioxanthone absorbs the energy and undergoes a photochemical reaction, resulting in the generation of free radicals. These free radicals initiate the polymerization process, leading to the rapid curing of the coating or ink. This property makes ITX an efficient and reliable photoinitiator for UV-curable systems. In addition to coatings and inks, 2-Isopropylthioxanthone finds extensive use in the production of dental restoratives, such as dental composites and adhesives. The photoinitiating capabilities of 2-Isopropylthioxanthone enable the rapid and controlled polymerization of these materials when exposed to UV light. This ensures quick and efficient dental procedures while maintaining excellent mechanical properties and aesthetics. Furthermore, 2-Isopropylthioxanthone is employed in the manufacturing of optical fibers and electronic devices. It acts as a sensitizer or photoinitiator in the preparation of photosensitive resins used for microfabrication processes. The precise and controlled nature of ITX-mediated photopolymerization makes it particularly suitable for intricate and delicate electronic components. Overall, 2-Isopropylthioxanthone plays a crucial role in UV curing technology, enabling fast and efficient curing of coatings, inks, adhesives, dental materials, and microfabrication processes. Its photoinitiating properties make it an indispensable component in various industries, contributing to improved productivity and high-performance end products. ¹

Cytotoxic effects

2-Isopropylthioxanthone is a photoinitiator commonly used in printing processes. In a study evaluating the cytotoxic effects of various chemicals on human normal embryonic lung fibroblasts, it was found that 2-Isopropylthioxanthone did not induce cytotoxicity on its own. However, when combined with 1,2-dichloropropane (DCP) and other photoinitiators such as 2,2-dimethoxy-2-phenylacetophenone (2,2-DMPAP), 2-ethylhexyl-4-(dimethylamino) benzoate (2-EHDAB), and methyl 2-benzoylbenzoate (MBB), the combination significantly induced cytotoxicity and apoptosis in the cells. This indicates that while 2-Isopropylthioxanthone may not pose a significant cytotoxic risk on its own, its interaction with certain chemicals, particularly DCP and other photoinitiators, can lead to increased cytotoxicity and potential health risks. Therefore, caution should be exercised when using these chemicals including 2-Isopropylthioxanthone in combination, especially in occupational settings to prevent respiratory diseases and occupational injuries. ²

Detection

2-Isopropylthioxanthone is a compound that can be found in milk and milk products as a result of its use as a photoinitiator in printing inks used for packaging. To detect 2-Isopropylthioxanthone contamination in milk, a fast screening method has been developed using high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). The method involves the direct analysis of milk samples with the addition of a deuterated 2-Isopropylthioxanthone solution in acetonitrile to serve as an internal standard and to precipitate proteins. This approach allows for isomeric specific analyses of 2-Isopropylthioxanthone and 4-ITX at levels as low as 6 microg/L with about 5% precision and accuracy. The method has been successfully used to check contamination in various milk products, such as soy milk and baby milk, as well as their packaging materials. Out of 37 milk samples analyzed, 16 were found to be positive for 2-Isopropylthioxanthone contamination with concentrations ranging from 173-439 microg/L for 2-Isopropylthioxanthone and from <6 to 25 microg/L for 4-ITX. This highly accurate and sensitive method can be used to ensure the safety and quality of milk products by detecting potential 2-Isopropylthioxanthone contamination. ³

Reference

1. 2-Isopropylthioxanthone. National Center for Biotechnology Information (2024). PubChem Compound Summary for CID 79633.

2. Kawasaki Y, Tsuboi C, Yagi K, et al. Photoinitiators enhanced 1,2-dichloropropane-induced cytotoxicity in human normal embryonic lung fibroblasts cells in vitro. Environ Sci Pollut Res Int. 2015;22(6):4763-4770.

3. Bagnati R, Bianchi G, Marangon E, Zuccato E, Fanelli R, Davoli E. Direct analysis of isopropylthioxanthone (ITX) in milk by high-performance liquid chromatography/tandem mass spectrometry. Rapid Commun Mass Spectrom. 2007;21(13):1998-2002.