Detection by coupled LC-photodiode array detection and high-resolution Orbitrap MS of dimethyl and diethyl yellow dyes used illegally in processed soymilk curd

Technical Overview of Orbitrap High Resolution Mass Spectrometry and Its Application to the Detection of Small Molecules in Food (Update Since 2012)

Food safety and quality issues are becoming increasingly important and attract much attention, requiring the development of better analytical platforms. For example, high-resolution (especially Orbitrap) mass spectrometry simultaneously offers versatile functions such as targeted/non-targeted screening while providing qualitative and quantitative information on an almost unlimited number of analytes to facilitate routine analysis and even allows for official surveillance in the food field. This review covers the current state of Orbitrap mass spectrometry (OMS) usage in food analysis based on research reported in 2012-2019, particularly highlighting the technical aspects of OMS application and the achievement of OMS-based screening and quantitative analysis in the food field. The gained insights enhance our understanding of state-of-the-art high-resolution mass spectrometry and highlight the challenges and directions of future research.

Analysis of illegal colourants (citrus red II, diethyl yellow, dimethyl yellow, metanil yellow and rhodamine B) in foods by LC-UV and LC-MS/MS

Synthetic colourants are highly regulated due to their correlation with a variety of health hazards. Regulatory services must be able to detect the substances in a cost-effective, efficient, and sensitive manner. LC-UV and LC-MS/MS methods have been developed to simultaneously detect five illegal colourants in foods, such as: citrus red II, diethyl yellow, dimethyl yellow, metanil yellow, and rhodamine B. This method showed good linearity (R ² > 0.99) and low limits of detection (0.09-0.19 mg kg^-1) and quantitation (0.26-0.58 mg kg^-1). The recoveries at three standard concentration levels ranged between 80.9% and 120%, with relative standard deviations below 12%. The expanded uncertainties determined for the five colourants in three food matrices were 8.2-19.4%. This method was applied to monitor five illegal colourants in imported and domestic beverages, candies, and sauces. None of the five colourants were found in any of the 510 samples. The method is suitable for quantitative analysis of five illegal colourants simultaneously in various foods and can be applied to improve current surveillance and inspection services.

Identification of the monobrominated derivative of Acid Red 52 (Food Red No. 106) in pickled vegetables

Two unknown dyes (purple and purplish-red) were detected by TLC in two pickled vegetable (sakura-zuke daikon) samples containing Acid Red 52 (AR) and New Coccine as food colorants. HPLC with diode-array detection and LC/MS analyses suggested that the purple dye is monobrominated AR and the purplish-red dye is its N-desethyl derivative, which would be generated mainly during sample preparation. For the identification of the purple dye, a reference compound was prepared by bromination of AR followed by isolation of the monobrominated AR, the structure of which was elucidated as 4'-brominated AR (4'BrAR) by LC/ToF-MS and (1)H-NMR spectroscopy. The purple dye was confirmed as 4'BrAR by comparison of its retention time, ultraviolet-visible spectrum and mass spectrum with those of the prepared reference compound. To our knowledge, this is the first report of the detection of 4'BrAR in foods.