Fundamental definitions and confusions in mass spectrometry about mass assignment, centroiding and resolution

• Resolution and resolving power are often defined in opposing ways.
• Resolution is the theoretical ability of the detector.
• Distinguishability is the ability of the detector achieved in practice.
• The distinguishability of a detector cannot be better than its resolution.

Even though the main steps of preprocessing and data analysis in liquid/gas chromatography coupled to mass spectrometry (MS) have been frequently reviewed in recent years, little attention has been paid to the initial processing of these data, from mass detection and centroiding to the use of the fundamental definitions, such as resolution. This article presents a current approach to the decomposition of the mass spectrum into mass peaks and the estimation of mass-centroid positions. We discuss recommendations on the use of fundamental definitions. We introduce the topological terms of distinguishability and discriminability to differentiate between the theoretical ability of a detector to distinguish adjacent MS peaks, and what can be achieved in practice.