Contaminants in our food? How to detect untargeted compounds and determine their identity
Identification of non-target and unknown contaminants and organic residues is a very challenging task becauseof the number of possible compounds. Food is a complex matrix and with present day technology to separate and identifyorganics amongst the thousands naturally found requires hyphenated chromatography to mass spectrometry. The use ofhigh resolution in both chromatographic separation and the mass spectrometer is needed to screen and identify compoundsnot being sought. High performance liquid chromatography with a hyphenated quadrupole time-of-flight mass spectrometer(HPLC/Q-TOF MS) is shown to successfully identify non-targeted compounds in complex samples. Examples using spikedmatrices show the utility of this technique. A non-targeted analysis of spinach shows that pesticides such as imadoclopridcan be screened using a pesticide database. A mycotoxins, in this example chaetocin, is found in ground black pepperby comparison to a control and identified through determination of the molecular formula and then searching a publicdatabase. Accurate mass MS/MS of non-targeted compounds are then compared to an exact mass library for identification.In the absence of library spectra, the MS/MS fragments are manually matched to possible identities by comparing accuratemass fragments to the structure of a proposed compound.