Empower Tip: Review Window and the Processing Method

Do you run steep gradients on your HPLC and the resulting baselines drift upward? Do you run steep temperature programs in the column oven of your GC and have a similar phenomenon? Did you ever want to subtract the rising baseline? It is very easy to do by Deriving a Channel and this will give us the opportunity to explore how we can mathematically combine channels.

We begin by bringing a sample set into Review and zooming in on the baseline of one of the injections. We see the rise in the baseline due to the gradient.

The first thing we need to do is give the blank injection a label either in the Sample Set method prior to acquiring the data or post run in Alter Sample.

Then we open the method set and derive a new channel. (Reviewed in Tip 48)

On the First (Only) Channel tab select the channel from the Channel drop down list. (This is single channel UV data so it is an easy choice.)

On the Second Channel tab select a mathematical operator, subtraction in this case.

Select the channel from the Channel drop down list.

Check the box that says From Injection Labeled and then enter the label for the blank in the empty field. Note the equation that Empower creates which says subtract the blank channel, from the injection labeled Blank, from all other channels.

Save the Derived Channel with a name, select the processing method in the channel table and save all changes to the Method Set.

Return to the Main Window, Apply the method set and now the baseline is flat.

Finally, Apply the Method Set to the blank injection and the result is a straight line because it is subtracted from itself.

It’s that easy!