Are peak splitting and peak fronting effects keeping you up at night?

You don’t have to just daydream about perfect peak shapes, you can actually achieve them! It’s time to address a few more unpleasant peak shapes that might end up ruining your chromatogram. Read on to find out how to get rid of the unfortunate phenomena of peak fronting and peak splitting if these are blocking your way to obtaining beautiful peaks.

My wife woke up in cold sweat the other night, nearly screaming her head off. The poor thing had just had a horrible nightmare. She dreamt that a chicken that consisted only of bones and a beating heart was running around the garden. I tried to calm her down by telling her about my own nightmares, but it didn’t work. Somehow she did not find this

asymmetrical peak shapes, chromatography, chromatogram

As terrifying as her boney chicken.

Well, okay, fine, I guess it’s true that these distorted horrible peaks are only the stuff of true chromatography horror. But if you find them as terrible as me and want to avoid turning these bad dreams into reality, read on to see if I can help with that.

In the last chromatography post, I talked about peak tailing and how to avoid seeing this phenomenon in your chromatograms. But as I mentioned then, there are also other nasty effects that you have to fight against in your quest for peak symmetry. So in this post, I’d like to focus on causes and solutions of peak fronting and peak splitting.

Let’s start with peak fronting in chromatography, shall we?

Peak fronting is observed less frequently than peak tailing, but when it does occur it looks like this:

peak fronting, chromatogram, chromatography

One of the causes of peak fronting is column overload.

A column has a certain maximal sample capacity. If this maximum is exceeded, the additional molecules cannot partition between stationary and mobile phase. Because of this, they elute faster from the column and can cause peak fronting. To reduce or eliminate the fronting, you could try reducing the sample amount you load on a column.

Another cause of peak fronting is incompatibility between sample solvent and mobile phase. To try to solve this problem, you could dissolve the sample in the mobile phase. Alternatively, you could introducing the sample into your chromatography system by using a solid loading approach as this method does not require sample solvent. For more information about sample loading techniques, check out the free Chromapedia Vol 2 guide.

Now that we’ve got peak fronting covered, let’s look at a third and final nightmare scenario: peak splitting. Peak splitting is the nasty bugger that looks like this when spewed out by the chromatography system:

peak splitting, chromatogram, chromatography

Whenever you notice peak splitting in your chromatogram, you should first check if the splitting occurs only in one to two peaks or if you observe splitting in nearly all of the peaks.

If only a single peak is affected, then your peak splitting is likely caused by a problem with the chemistry and the actual separation. One possible solution would be for you to optimize the mobile phase conditions. If this doesn’t fix the peak splitting effect, then try to select another stationary phase to improve the separation. Check out a few ideas on how to optimize mobile phases and stationary phases in my past posts.

If most or all your peaks are affected, then peak splitting is likely caused by column-related issues. For example, the presence of a void at the inlet of the column or channeling in the packing bed can result in peak splitting. If you are using pre-packed cartridges, the only way to address this issue to use a new cartridge. This might be a good time to check if you are using the optimal cartridge for your needs, as I’ve written about before. Check out our cartridge selection tool we’ve developed to help with your decision making process.

Alternatively, partially clogged inlet frits can lead to peak splitting. To eliminate this effect, you can either try filtering your samples before loading them on the column. Alternatively, you could use a solid loading injection technique to prevent peak splitting from occurring.

I sincerely hope this post can be your peak fronting and peak splitting dreamcatcher, so that you eliminate these effects from your chromatograms and from your bad dreams.

Are there other chromatography problems keeping you awake all night? Leave a comment below and see if I can help you in a future post.

Till next time,

The Signature of Bart Denoulet at Bart's Blog