title: Detection by coupled LC-photodiode array detection and high-resolution Orbitrap MS of dimethyl and diethyl yellow dyes used illegally in processed soymilk curd.
abstract: An efficient non-target dye-screening system consisting of a liquid chromatography photodiode array coupled with a high-resolution mass spectrometer (HRMS) is described. Visible absorption spectroscopy assisted in locating the peak of an unknown dye in HRMS chromatograms which allowed the accurate molecular weight of the unknown to be obtained. In a study of the adulteration of processed soymilk curd (tofu) with dimethyl yellow, an unexpected unknown dye was discovered. The compound was further purified by gel permeation chromatography and identified by HRMS and proton nuclear magnetic resonance (NMR) as diethyl yellow (solvent yellow 56). This is the first time that diethyl yellow has been reported in foods. The authentic diethyl yellow was then purchased and used as a quantitative standard. Tofu products and their ingredients associated with tofu processing were surveyed. Analysis showed the source of diethyl yellow could be traced to emulsifiers used as ingredient in tofu products. Surveillance work found the concentrations of diethyl yellow ranged from several μg kg(-1) (ppb) in the tofu products to up to hundreds of mg kg(-1) (ppm) in the emulsifiers.
authors.affiliation: a Taiwan Food and Drug Administration , Taipei City , Taiwan.
authors.forename: Mingchih
authors.initials: M
authors.lastname: Fang
authors.affiliation: a Taiwan Food and Drug Administration , Taipei City , Taiwan.
authors.forename: Chia-Fen
authors.initials: CF
authors.lastname: Tsai
authors.affiliation: a Taiwan Food and Drug Administration , Taipei City , Taiwan.
authors.forename: Ching-Hao
authors.initials: CH
authors.lastname: Kuo
authors.affiliation: a Taiwan Food and Drug Administration , Taipei City , Taiwan.
authors.forename: Hwei-Fang
authors.initials: HF
authors.lastname: Cheng
mesh_terms: D001555:Benzene Derivatives / Q000302:isolation & purification*; D002850:Chromatography, Gel; D004396:Coloring Agents / Q000302:isolation & purification*; D045703:Emulsifying Agents / Q000737:chemistry; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods*; D005506:Food Contamination / Q000032:analysis*; D059022:Food Safety; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D008970:Molecular Weight; D045730:Soy Foods / Q000032:analysis*; D013624:Taiwan
chemical_list: D001555:Benzene Derivatives; D004396:Coloring Agents; D045703:Emulsifying Agents
keywords: Orbitrap; diethyl yellow; dimethyl yellow; high resolution mass spectrometry; soymilk curd; tofu