Rapid detection of illegal colorants on traditional Chinese pastries through mass spectrometry with an interchangeable thermal desorption electrospray ionization source

[Display omitted] •An ambient mass spectrometer featuring an interchangeable TD–ESI and a conventional ESI is reported.•A dual-working mode is feasible after switching to a TD–ESI source from a ESI source coupled to LC.•Both qualitative screening analysis and quantitative confirmatory analysis have been performed.•Qualitative screening was complete within approximately 30 s for each analysis. Ambient mass spectrometry using an interchangeable thermal desorption/electrospray ionization source (TD–ESI) is a relatively new technique that has had only a limited number of applications to date. Nevertheless, this direct-analysis technique has potential for wider use in analytical chemistry (e.g., in the rapid direct detection of contaminants, residues, and adulterants on and in food) when operated in dual-working mode (pretreatment-free qualitative screening and conventional quantitative confirmation) after switching to a TD–ESI source from a conventional ESI source. Herein, we describe the benefits and challenges associated with the use of a TD–ESI source to detect adulterants on traditional Chinese pastries (TCPs), as a proof-of-concept for the detection of illegal colorants. While TD–ESI can offer direct (i.e., without any sample preparation) qualitative screening analyses for TCPs with adequate sensitivity within 30 s, the use of TD–ESI for semi-quantification is applicable only for homogeneous matrices (e.g., tang yuan).