Confirmation of the identity of residues using quadrupole time-of-flight mass spectrometry

Tandem mass spectrometry (MS/MS) has become a very important tool in bio-analysis, including residue analysis. The combination of a quadrupole and a time-of-flight mass analyser (Q-TOF mass spectrometer) provides an instrument with particularly interesting characteristics, also for residue analysis, compared to the more common triple quadrupole instruments. Especially the accurate mass measurement capabilities, the full scan sensitivity of time-of-flight mass analysis and the possibility of information dependent acquisition are of interest. The main field of application therefore is qualitative analysis, i.e. the identification of unknowns. To illustrate the potential of a Q-TOF mass spectrometer regarding the analysis of residues, two examples from literature are given, which detail the detection of unknowns in illegal cocktails. In addition, a third new experimental study is described about the MS analysis of unknown mixtures of growth promoters using accurate mass. Nevertheless, Q-TOF mass spectrometric applications in the field of, especially, food residue analysis seem to be lagging behind. Residue analysis being a mainly quantitative type of work, the relatively limited quantitative reputation of a Q-TOF mass spectrometer system is probably the culprit.