page_title: Mass chromatogram
section_title: Extracted-ion chromatogram (XIC)
hierarchical_section_title: Mass chromatogram / Extracted-ion chromatogram (XIC)
caption_attribution_description: English: an example extracted ion chromatogram (XIC) from an LC-MS analysis
context_page_description: A mass chromatogram is a representation of mass spectrometry data as a chromatogram, where the x-axis represents time and the y-axis represents signal intensity. The source data contains mass information; however, it is not graphically represented in a mass chromatogram in favor of visualizing signal intensity versus time. The most common use of this data representation is when mass spectrometry is used in conjunction with some form of chromatography, such as in liquid chromatography–mass spectrometry or gas chromatography–mass spectrometry. In this case, the x-axis represents retention time, analogous to any other chromatogram. The y-axis represents signal intensity or relative signal intensity. There are many different types of metrics that this intensity may represent, depending on what information is extracted from each mass spectrum.
context_section_description: In an extracted-ion chromatogram (XIC or EIC), also called a reconstructed-ion chromatogram (RIC), one or more m/z values representing one or more analytes of interest are recovered ('extracted') from the entire data set for a chromatographic run. The total intensity or base peak intensity within a mass tolerance window around a particular analyte's mass-to-charge ratio is plotted at every point in the analysis. The size of the mass tolerance window typically depends on the mass accuracy and mass resolution of the instrument collecting the data.  This is useful for re-examining data to detect previously-unsuspected analytes, to highlight potential isomers, resolve suspected co-eluting substances, or to provide clean chromatograms of compounds of interest.  An extracted-ion chromatogram is generated by separating the ions of interest from a data file containing the full mass spectrum over time after the fact; this is different from selected-ion chromatograms, discussed below, in which data is collected only for specific m/z values.
caption: An example extracted-ion chromatogram from an LC-MS analysis.
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