Introduction to LiRTMaTS

Untargeted metabolomics studies routinely apply liquid chromatography-mass spectrometry (LC-MS) to acquire data for hundreds or low thousands of metabolites and exposome-related (bio)chemicals. The annotation or higher-confidence identification of metabolites and biochemicals can apply multiple different data types (1) chromatographic retention time, (2) the mass-to-charge (m/z) ratio of ions formed during electrospray ionisation for the structurally intact metabolite or (bio)chemical and (3) fragmentation mass spectra derived from MS/MS or MSn experiments.

Chromatographic retention time is a complementary data type when compared to m/z and MS/MS data. Method-specific retention time (RT) libraries can be constructed by the analysis of pure metabolite standards applying the same assay and reporting the detected RT. The library RT can be compared to RT of a metabolite detected in an untargeted metabolomics study to aid in the annotation or identification of metabolites. The LiRTMaTS is a Python package and easy-to-use software for matching RTs detected in an untargeted metabolomics study to RTs present in a RT library. Any RT library can be applied though this RT library should be specific to the LC-MS assay applied (RT libraries are not transferable across different LC-MS assays). All matches within a RT range are reported.