has_metric_category has_units has value type n-tuple ID based metric single run based metric retention time metric MS2 metric obsolete identified MS2 quarter RT fraction true MS:4000188 MS:4000181 OBSOLETE. The interval used for acquisition of the first, second, third, and fourth quarter of all identified MS2 events divided by retention time duration. RT-MSMS-Q4 RT-MSMS-Q3 The metric informs about the dynamic range of the MS2 identification process along the chromatographic separation. For MS2 scans, the comparability of the values depends on the acquisition mode and settings to select ions for fragmentation. MS RT-MSMS-Q2 RT-MSMS-Q1 fraction