has_metric_category has_units has value type n-tuple ID free metric single run based metric retention time metric MS2 metric obsolete MS2 quarter RT fraction true MS RT-MSMS-Q4 RT-MSMS-Q3 MS:4000056 RT-MSMS-Q2 MS:4000185 RT-MSMS-Q1 The metric informs about the dynamic range of the acquisition along the chromatographic separation. For MS2 scans, the comparability of the values depends on the acquisition mode and settings to select ions for fragmentation. OBSOLETE. The interval used for acquisition of the first, second, third, and fourth quarter of all MS2 events divided by retention time duration. fraction