Non-visible print set-off of photoinitiators in food packaging: detection by ambient ionisation mass spectrometry

Direct analysis in real time coupled to time-of-flight mass spectrometry (DART/TOF-MS) was used to detect the non-visible set-off of photoinitiators on the food contact surface of three different packages. The samples were intentionally under-cured to provoke set-off. Twelve commercially available photoinitiators were included in the ink formulations including α-amino-, morpholino, and α-hydroxy benzophenones, thioxanthones, aryl-phosphine oxide and three polymeric versions of these. Major colours of the packages’ prints were analysed, as well as the specific areas of the inner surface in contact with them. Larger quantities of photoinitiators were detected on the food contact areas in contact with the darker colours of the images. Speed-cure 7005 and 4-phenylbenzophenone were the compounds most susceptible to set-off in each of the samples by DART response. An identification protocol for unknown set-off compounds was tested, resulting in the set-off detection of diethylene glycol ethers, erucamide and acrylates, and confirmed by solvent extraction GC-MS analysis. Finally, DART/TOF-MS was scanned across transects of the food contact side of packages to map the presence of photoinitiators. Higher photoinitiator signals were observed in patterns corresponding to the printed image, suggesting DART/TOF-MS might “image” print set-off.     

基于AMI-MS 法的印刷背面粘脏测试方法研究

利用AMI-MS(Ambient Ionization-accurate Mass)质谱技术,检测和识别食品包装不可见背面粘脏化合物,并识别基本组分。结果表明,AMI-MS 可在不进行任何样品处理的条件下,直接测得其背面粘脏化合物的成分,而且可以通过质谱对其化合物结构进行确认,相比常用的GC-MS 法,具有简便、快速、准确、便于高通量分析等优势。     

Migration from printing inks in multilayer food packaging materials by GC-MS analysis and pattern recognition with chemometrics

Inks and varnishes used in food packaging multilayer materials can contain different substances that are potential migrants when packaging is in contact with food. Although printing inks are applied on the external layer, they can migrate due to set-off phenomena. In order to assess food safety, migration tests were performed from two materials sets: set A based on paper and set B based on PET; both contained inks. Migration was performed to four food simulants (EtOH 50%, isooctane, EtOH 95% and Tenax^®) and the volatile compounds profile was analysed by GC-MS. The effect of presence/absence of inks and varnishes and also their position in the material was studied. A total of 149 volatile compounds were found in migration from set A and 156 from set B materials, some of them came from inks. Quantitative analysis and a principal component analysis were performed in order to identify patterns among sample groups.     

Identification of print-related contaminants in food packaging

Since the UV ink photoinitiator (PI) isopropylthioxanthone (ITX) was discovered in packaged milk, studies of print contamination have focused primarily on PIs but have also included amine synergists. Many other substances are used or formed during the print process, yet their identity and set-off properties have yet to be catalogued in food packaging. Three different techniques: direct analysis in real-time high-resolution mass spectrometry (DART-HRMS), gas chromatography-mass spectrometry (GC-MS) and ultra-high-pressure liquid chromatography electrospray ionisation/HRMS (UHPLC/ESI-HRMS) were used to detect and identify print-related molecules from the food-contact and print surfaces of three different packages with under-cured prints. This approach tentatively identified or confirmed 110 compounds, including 35 print-related molecules. The majority of compounds identified on food-contact surfaces were packaging monomers/byproducts, solvents/plasticisers, antioxidants/degradants or slip agents/lubricants. Of these, 28 showed evidence of set-off. The identities of 16 PIs, seven known scission products and five probable PI degradants were confirmed, most showing signs of set-off. Of the print-related molecules, at least five are novel print contaminants such as 4-morpholin-4-yl-benzaldehyde or 3-phenyl-2-benzofuran-1(3H)-one.     

隧道交通虚拟仿真系统

将虚拟现实（Vinual Reality—VR）技术与交通流仿真技术相结合,设计了虚拟交通流仿真系统应用于隧道交通流研究。该项技术也称交互式的动态虚拟实现技术,使用发车、跟车、变道等模型对隧道内的交通状况进行了仿真。为我国隧道交通工程的研究和设计提供了直观、科学的仿真手段。