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What is the difference between direct injection and other types of LCMS

Last Modified: 2020-02-11
Can any one help with LC/MS R packages?

The xcms R package for LCMS is very versitile.  It distinguishes between Grouping FTICR-MS data with xcms, LCMS and LCMSMS.  

Quoting from the documentation
This document describes how to use xcms for the analysis of direct injection mass spec data, including peak detection, calibration and correspondence (grouping of peaks across samples). Prior to any other analysis step, peaks have to be identified in the mass spec data. In contrast to the typical metabolomics workflow, in which peaks are identified in the chromatographic (time) dimension, in direct injection mass spec data sets peaks are identified in the m/z dimension. xcms uses functionality from the MassSpecWavelet package to identify such peaks.

I cannot find any information related to direct injection.  I understand FTCIR-MS and the reason why peaks can be identified in the m/z dimension, but I don't understand the concept of direct injection and whether this concept is associated with FTICR-MS only and not with LC/MS or LC.MS/MS.
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