Mass spectrometric identification criteria

For confirmation of target compounds, LC relative retention time criteria (retention time window <2.5%) and mass spectrometric identification criteria need to be fulfilled. The latter are based on the concept of identification points (EC, 2002). For accurate mass screening using TOF or Oibitrap MS instraments, no criteria are described. Recently, some propositions for these types of instraments were made by Nielen et al. (2007). For high-resolution screening (resolution >20,000 and a mass accuracy <5 mDa), these authors proposed two identification points. Each product ion (low-mass- resolution MS) also contributes two points. Tlius, acquiring a high-resoludon precursor ion in combination with at least one product ion and the LC relative retention time meets the minimum requirement of four identification points. 

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