title: Determination of 2-isopropyl thioxanthone and 2-ethylhexyl-4-dimethylaminobenzoate in milk: comparison of gas and liquid chromatography with mass spectrometry.
abstract: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) have been compared for the analysis of 2-isopropyl thioxanthone (ITX) and 2-ethylhexyl-4-dimethylaminobenzoate (EHDAB). Pressurized liquid extraction (PLE) was applied for the extraction of ITX and EHDAB from milk and milk-based beverages. Samples were homogenized with sea sand and anhydrous sodium sulfate, and were extracted with ethyl acetate at 100 degrees C and 10.3 x 10(6) Pa in one cycle of 10 min at 90% flush. Both, GC-MS and LC-MS/MS were suitable to determine these photoinitiators in the PLE extracts, providing appropriate identification and quantification. The recoveries obtained ranged from 70 to 99% for ITX and from 70 to 95% for EHDAB. These recoveries were equal as those obtained by a conventional liquid-liquid partitioning with acetonitrile and tert-butyl methyl ether-hexane. The quantification limits using GC-MS, based on a signal-to-noise ratio of 10, were 0.5 microg/L for ITX and 1 microg/L for EHDAB. The repeatability of the method, as indicated by the relative standard deviations, was within the range 0.9-16.1%. The same parameters calculated using LC-MS/MS result in quantification limits of 0.1 microg/L for ITX and 0.02 microg/L for EHDAB and repeatability within the range 5.2-19.4%. These results pointed out that both techniques are appropriate to determine these compounds in food samples. The method was applied to milk and milk-based beverages from different supermarkets. The ITX and EHDAB contents ranged from 2.5 to 325 microg/L and from 8 to 126 microg/L, respectively.
authors.affiliation: Laboratori de Bromatologia, Facultat de Farmàcia, Universitat de València, Av, Vicent Andrés s/n, 46100 Burjassot, Valencia, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Gil-Vergara
authors.forename: Cristina
authors.initials: C
authors.lastname: Blasco
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Picó
mesh_terms: D010129:4-Aminobenzoic Acid / Q000032:analysis; D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods*; D013058:Mass Spectrometry / Q000379:methods*; D044004:Xanthones / Q000032:analysis*; D062366:para-Aminobenzoates
chemical_list: D044004:Xanthones; D062366:para-Aminobenzoates; D010129:4-Aminobenzoic Acid; C041981:padimate-O