For research use only. Not for use in diagnostic procedures.
A transition is flagged in the MultiQuant® software results table with the reason "Ion Ratio".
If the ion ratio has failed for a particular analyte, it means that the actual ion ratio exceeds the allowed range for the expected ion ratio as defined in the Outlier Settings in the quantitation method. Expected ion ratios are calculated by averaging the ion ratios of the standards used for the calibration curve.
To understand why an ion ratio fails, compare the failed ion ratio (highlighted in the results table in red) to the expected ion ratio for that set of transitions. (If not showing, the expected ion ratio can be viewed by selecting it from the column settings.) Because the ion ratio is directly related to the peak areas for the transitions defining the analyte, ion ratio failures can be related to integration differences between the sample and the standards. Adjusting the integration parameters (such as noise percentage) may allow for more consistent integration between samples and standards and allow for the ion ratios for an unknown sample to be consistent with those calculated for a standard.
Often discrepancies in peak integration is not the only reason why the "ion ratios" outlier reason is produced. Ion ratios will typically fail in cases where the peak area from a single (or both) MRM transitions saturate the detector. Ion ratio failures also result when the peak selected is not actually that of the intended analyte. In this case, the retention time of the analyte should be closely inspected in the calibrators and compared to that of analyte in the unknown sample. Additionally, if an interference is present at the same retention time as that of the analyte, an ion ratio failure would also be observed. This list is not inclusive of all reasons why ion ratios fail, but notes some of the most common examples.