How to use the Threshold Sample in Comparative View
To utilize comparative view to its fullest, one must set 3 three properties.
- Method-Limits-Threshold setting – this setting allows the user to set the height of the horizontal threshold bar in data review. There are two settings.
- Threshold – a fixed peak height amount
- % of Threshold the Sample – dynamic threshold according the peak height of the specified Threshold sample, as described below.
- Batch view-samples-groups column – this setting assigns samples to groups that are displayed horizontally in the comparative view peaks panel. A unique alpha numeric symbol is used to assign a sample to a group. Each sample with the same symbol is a member of that group. The samples are shown side by side in the peak review panel and are ordered left to right by descending order in the sample grid above.
- Batch view-threshold samples – the setting allows the user to assign a threshold sample for each group. Any member of the group can be set as the threshold sample. However, only one sample can be utilized at a time in the group. If you want one particular sample to be used as the threshold across the batch make sure it is a member of all the group. For example if you used numbers for the group name and you have 10 groups, the entry for this sample in the groups column would be 1,2,3,4,5,6,7,8,9,10.
The settings in the examples above allow for the display shown below.
The tall red vertical bar marks the expected retention time and the smaller vertical bars are the edges of the retention time window. Both set in the method parameters for each compound. This allows you to see the drift of chromatography within the sample group. The horizontal red line is the threshold as set in the method as a fixed amount or relative percentage of the threshold sample, as set in the method.
A point to note, there were a few instances where everything was setup properly but nothing displayed in the Comparative view. It was found that some older video drivers not comply with technologies Microsoft used to render the images in this complex grid. However, the issue was fixed in all cases by updating to the latest video drivers for the PC.