title: Determination of isopropyl-9H-thioxanthen-9-one in packaged beverages by solid-phase extraction clean-up and liquid chromatography with tandem mass spectrometry detection.
abstract: A simple method was developed and validated for the trace determination of 2-isopropylthioxanthone (ITX) in packaged drinks. Samples were extracted from the food matrix using acetonitrile:water (60:40, v/v), and further subjected to clean-up and preconcentration using solid-phase extraction prior to analysis by liquid chromatography-tandem mass spectrometry using multiple reaction monitoring (MRM) mode. The use of 2-isopropyl-[(2)H7]thioxanthen-9-one was incorporated into the method as an internal standard. Excellent 3-day interday precision data (RSD 0.72%, n=10), and intraday precision data (RSD 0.52%, n=10) were obtained on a 0.10 microg/L standard solution. Spiked samples (n=8) were used to gauge the accuracy of the method at the concentration levels of 2.5, 100, and 500 microg/kg in food; recoveries ranged from 97.0 to 103.0%. These excellent validation data suggest the exciting possibility of using this method for the determination of low levels of ITX migrating from printed food packaging materials into beverages with a method quantitation limit of 0.50 microg/kg. For the first time, analysis on a range of milk, juice, tea and yoghurt drinks, as well as their respective food packaging materials were performed for comparative studies on their ITX content.
authors.affiliation: Food Laboratory, Centre for Analytical Science, Health Sciences Authority, 11 Outram Road, Singapore 169078, Singapore. SUN_Cuilian@hsa.gov.sg
authors.forename: Cuilian
authors.initials: C
authors.lastname: Sun
authors.forename: Sheot Harn
authors.initials: SH
authors.lastname: Chan
authors.forename: Dan
authors.initials: D
authors.lastname: Lu
authors.forename: Hui Min Wendy
authors.initials: HM
authors.lastname: Lee
authors.forename: Bosco Chen
authors.initials: BC
authors.lastname: Bloodworth
mesh_terms: D001628:Beverages / Q000032:analysis*; D002853:Chromatography, Liquid / Q000379:methods*; D005504:Food Analysis; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013892:Thioxanthenes / Q000737:chemistry*
chemical_list: D013892:Thioxanthenes; C518329:isopropyl-9H-thioxanthen-9-one