Light and heavy dansyl reporter groups in food chemistry: amino acid assay in beverages

5-Dimethylamino-1-sulfonyl naphthalene (DNS, commonly referred as dansyl) is a functionality, bearing well-establishedproperties in directing the fragmentation, by mass spectrometry (MS), of the corresponding ionized sulfonylated derivatives.This property is shared also by its labeled analogs. The use of d0/d6 DNS derivatives is now exploited in the application ofthe well-established isotope dilution mass spectrometric approach in the assay of complex mixtures. A new method for thequantitation of amino acids (AAs) in beverages is therefore presented, which relies on liquid chromatographic separation oftheir N-dansylated derivatives followed by comparative electrospray tandem MS/MS of the d0/d6 isobaric mixtures.Labeled and unlabeled DNS derivatives of the selected AAs are readily available by microwave-assisted synthetic protocols.The novelty of the method is represented by the use of heavy and light DNS-isotopologue providing suitable reporter groups.Multiple-reaction monitoring has been applied in the assay of AAs in wine, pineapple juice and bergamot juice with good-toexcellentresults as proved by both relative standard deviation, lower than 15%, and by the accuracy values in the range