Relatively reliable and rapid identification of colorant compounds in food matrices by HPLC-DAD-QTOF-MS combined with theoretical calculation.

A new convenient method for identifying colorant compounds (CCs) in food matrices was developed using high-performance liquid chromatography with a diode array detector and quadrupole-time-of-flight mass spectrometer (HPLC-DAD-Q/TOF-MS) combined with theoretical calculations. A model sample containing three typical CCs was completely separated via HPLC-DAD. The obtained 3D ultraviolet-visible (UV-vis) spectra revealed the maximum absorption wavelengths (MAWs) of all CCs (yellow, 430 nm; red, 520 nm; blue, 620 nm) in the range of 400-800 nm, and their colors were determined based on their MAWs. Temporary structures of the CCs were obtained using Q/TOF-MS analysis. Theoretical calculations were then performed to obtain the theoretical MAWs and colors of the CCs according to their calculated UV-vis spectra based on temporary structures. The structures of the CCs were confirmed without the need for authoritative standards by comparing the consistency between their experimental and theoretical MAWs and colors. This method is particularly suitable for identifying CCs or compounds with UV-Vis absorption, including new compounds, compounds for which standards are difficult to obtain, and known compounds without reporting relevant molecular information.