A picture is worth 1000 words: creating great GPC/SEC figures
Generating high quality GPC/SEC data in the lab is exciting! But what makes it even more exciting is being able to share that data with colleagues, customers, and anyone else that can benefit. And while numerical data may contain detailed differences, sometimes it’s easier to drive a point home through well-organized figures. As the saying goes, a picture is worth a thousand words!
In this case, that picture might be a comparison between different samples. Or an expansion of a sample’s chromatogram that highlights a subtle feature. Whatever your goal, a quality visual presentation of your GPC/SEC data can go a long way toward supporting your conclusions. In this post, I’ll describe a few tips for using the OMNISEC v10+ and OmniSEC v5 software platforms to create great GPC/SEC figures.
Why are there two different software platforms?
The reason I specify OMNISEC v10+ and OmniSEC v5 is because they are two separate software packages that are used with different Malvern Panalytical GPC/SEC products. If you are unsure of which one you’re using, you can look at the very top left of the software interface, read the descriptions below, and/or use the embedded videos to help you decide.
OMNISEC v10+ is used for instrument control, data collection, and data analysis with a complete OMNISEC system or an OMNISEC REVEAL connected to a different front end, such as a Waters ACQUITY APC unit.
OmniSEC v5 is used for data collection and analysis when working with a SEC-MALS 20 unit that has been added on to an existing system from another manufacturer. It is important to note that OMNISEC v10+ is used when working with a SEC-MALS 20 unit paired with OMNISEC REVEAL. This software platform is also used to perform branching calculations and with legacy Viscotek brand instruments such as the TDA305, 270, or RImax configurations.
Many of the features are similar on both software platforms, so I will include figures and examples from both throughout this post.
Zooming in and out
The simplest way to adjust figures in both software platforms is to click and drag to expand the selected area. If you go to far, you can simply right-click and choose Zoom back to undo the last zoom, or Full zoom out to return to the original view. In v10+ these two functions are also accessible through toolbar icons; in v5 the tool bar contains a Zoom back button.
Moving individual axes
A convenient way to highlight a particular part of your chromatogram is to adjust the axes. All of the x and y axes in both v10+ and v5 software platforms can be moved by clicking and dragging. I find this especially helpful when separating out the signals from multiple detectors. The default view is to normalize each response, which usually results in the viscometer baseline higher than the others because of the delay peak. By clicking and dragging each individual axis I can arrange them so they’re stacked. This helps highlight features that are not present in every detector, such as the light scattering response from 10-13 mL in the multi-detector chromatogram below.
Setting minimum and maximum axis values
Another way to adjust axes in figures is to use the grey squares at each end to set minimum and maximum values. These grey squares are present in both v10+ and v5; they are indicated below on a raw data example of BSA from v5.
As you can see, there is a lot of empty chromatogram space before and after the sample peaks. In order to highlight the BSA and eliminate dead space in the image, the x-axis could be focused on the area between 8 and 20 mL. In order to do this, I clicked on the left grey square and typed “8” and then Enter, then clicked on the right grey square and typed “20” and then Enter. The resulting chromatogram is below.
I use this feature mainly when setting the minimum and maximum values of the x-axis. This way, when I’m presenting multiple figures, I can ensure they’re all showing the same portion of the chromatogram, which allows for valid visual comparisons.
Shrinking and expanding an axis
In the example above in which I spaced out four detector signals, I clicked and dragged each axis to stagger the baselines but then had to shrink the signals so all detector responses remained visible. I could have done this using the grey squares for each detector response, but since I wasn’t worried about the specific minimum and maximum values I used a different, quicker method.
To adjust the RI signal’s scale, I placed the cursor on the RI signal’s axis and hovered it at the same level as the RI signal’s baseline. When the cursor is hovered over an axis in v10+, vertical or horizontal, it will change to the icon highlighted below. When I use the mouse scroll wheel and scroll up, the axis will shrink causing the detector signal to expand. When scrolling down, the axis will expand, causing the detector signal to shrink.
It’s important to note that this expansion/contraction occurs based around the location of the cursor, which is why I make a point to hover as close to the detector baseline value as possible. In v5 the cursor doesn’t change appearance, but the functionality remains the same.
Single axis vs. multi-axis options
The Overlay view in both software platforms (and Distribution Plot in v10+) is a fantastic tool for creating figures to compare samples to each other, or even multiple injections of the same sample. With this plot you have the option for each chromatogram to have its own axis or for all signals to share a single y-axis. Depending on your data and the goal of a particular figure, one option may be better suited than the other.
For example, if you want to compare features of different injections and not the magnitude or peak areas, then using the multi-axis view will allow you to adjust each chromatogram independently. If you are comparing multiple injections of the same sample and want to investigate why their recovery values are different, then using a single axis will plot everything on the same scale allowing for fair comparisons.
The right-click menus on the Overlay views in v10+ (left) and v5 (right) are shown below. In v10+ you are able to turn off single axis view to access multi-axis view, and in v5 you have the option to Toggle Multi-Axis View on or off. There are lots of other options available as well – play around and check them out!
Using these plots in presentations, documents, etc.
Once you’ve arranged the data and everything looks perfect, you can easily copy and paste these figures into another document for reports, presentations, emails, etc.
In v5, you simply ensure the plot you want to copy is the active window (there will be an orange border around the area to be copied, as opposed to a blue border around the non-active window plots), then press Ctrl + C to copy. Move to your desired destination and use Ctrl + V to paste an image of the plot.
You can also right-click on the plot and select Copy Graph from the menu. It is important to note that Copy Data will copy the numerical data used to generate that plot, not an image. Stay tuned for more on Copy Data in an upcoming post!
In v10+ you can right-click on the figures and select Copy graph to copy the image. Then once you’re in your document you can Ctrl + V or right-click and select Paste to insert an image of the plot.
Final thoughts
In conclusion, I hope these tips help enhance your data presentations. There are plenty of other features in both versions of the software that I didn’t have space to discuss here. Explore the right-click menus (and the toolbar menus in v5) and don’t be afraid to try something new! If you have any questions, please don’t hesitate to contact us or email me directly at kyle.williams@malvernpanalytical.com.
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