Determination of low-level ink photoinitiator residues in packaged milk by solid-phase extraction and LC-ESI/MS/MS using triple-quadrupole mass analyzer

• Published in: Analytical and bioanalytical chemistry 2009-12, Vol.395 (7), p.2359-2370
• Main Authors: Shen, Dong-xu, Lian, Hong-zhen, Ding, Tao, Xu, Jin-zhong, Shen, Chong-yu
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Biochemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Extraction; Food Science; Laboratory Medicine; Mathematical analysis; Milk; Monitoring/Environmental Analysis; Original Paper; Other chromatographic methods; Photoinitiators; Residues; Spectrometric and optical methods
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-009-3115-z

A confirmatory and quantitative method based on liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) has been developed for simultaneous determination of seven photoinitiator residues: benzophenone, (1-hydroxycyclohexyl)phenylketone (Irgacure 184), isopropylthioxanthone (ITX), 2-ethylhexyl-(4-dimethylamino)benzoate (EHA or EHDAB), 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone (Irgacure 907), (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) and 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone (Irgacure 369) in packaged milk and related packaging materials. Residues of photoinitiators were extracted from milk using acetonitrile, and further enriched and purified on HLB solid-phase extraction cartridges prior to being analyzed by LC-ESI/MS/MS with selected reaction monitoring mode, while photoinitiators in packaging materials were extracted using the same solvent. Satisfactory recovery (from 80 to 111%), intra- and inter-day precision (below 12%), and low limits of quantification (from 0.1 to 5.0 μg kg⁻¹) were evaluated from spiked samples at three concentration levels (5.0, 10.0 and 25.0 μg kg⁻¹ for Irgacure 184 and 2.5, 5.0 and 25.0 μg kg⁻¹ for others). These excellent validation data suggested the possibility of using the LC-ESI/MS/MS method for simultaneous determination of low-level photoinitiator residues migrating from printed food-packaging materials into milk. The method has been successfully applied to the analysis of real samples of different fat contents ranging from 8 to 30 g L⁻¹. The photoinitiator residues were revealed to be higher in milk with higher fat content and the most important contaminations were benzophenone and ITX in concentration ranges of 2.84-18.35 and 0.83-8.87 μg kg⁻¹, respectively. [graphic removed]