has_metric_category has_units has_value_concept has value type n-tuple ID based metric single run based metric retention time metric targeted compound retention time deviation quantiles MS:4000241 From the distribution of the deviations of the observed from the expected retention times (observed minus expected) of a set of targeted/expected compounds (e.g., from a QC mix), the quantiles. For example, a value triplet represents the quartiles Q1, Q2, Q3. Only detected compounds contribute to the distribution. The compounds need to be confidently identified, ideally by several characteristics (e.g., mass spectrum and retention time). MS A tight distribution close to zero indicates that all compounds within a run are close to their expected retention times; a shifted Q2 indicates a systematic retention time drift, and a wide interquartile range (Q3-Q1) indicates compound-dependent deviations. second