Don’t mess with my flow! How to solve three common solvent flow problems in chromatography

Nobody likes to be impeded during their lab work, but is there anything more annoying than a disturbance in your solvent flow during a chromatography run? Before you start pulling your hair out, check out this post on three common causes of solvent flow problems and how to solve these issues. Ready to go with the flow? Then read on.

I went to the zoo with my nephew last weekend. One of the animals he found most captivating was the beaver. I was happy to recall a few stories of beavers I had seen in the wild while attending a scientific conference in Canada. It was amazing to see the dams they had built and how they could block whole streams with their woodwork to create ponds for themselves.

I remember, even back then, I was a bit irked at the thought of a dam, nonetheless. You see, I am no fan of blockages of any sort. Not in my drainage pipes, not in my bubble tea straws and definitely not in my chromatography system!

So, I’ve decided to dedicate this blog to helping you achieve a smooth flow in chromatography by showing you how to tackle three common causes of solvent flow disturbance and how to deal with these issues.

Now the first tissues are all about air bubbles in your hoses. If these air bubbles appear in your inlet line and your outlet line, they can block your solvent flow, just like the wood pieces from the beaver block the stream flow.

But don’t let me get ahead of myself, let’s explore these, one by one.

Issue 1: Air bubbles in inlet line (thinner hose) to the flash pump

Solution: To solve this problem, check the fittings of your system. In a Pure chromatography system, for example, there are four inlets located at the rear of the device. Manually test if these are tight and that the hoses are not bent. On the other end of the solvent inlet hose, you have the filter. Make sure that this fitting is also very tight and properly connected.

Issue 2: Air bubbles in outlet line (thicker hose) or pump head

Solution: Rinse system and pump with hot water to get rid of any crystallization or other deposits. If you own a rotary evaporator, you can use the heating bath to help you with this. Briefly, heat water to 60°C to 70°C in the water bath, move your solvent inlet line one from the solvent bottle to the heating bath. You now have to flush the system over the manual control or the service menu of your chromatography system. If possible, select a rinsing program from the service menu of your chromatography system. Here, the flow rate should be set to maximum, 250 ml/min. Before you start, make sure your waste hose is also in the waste bottle and the bypass is installed on your system.

Just an extra tip, once you start the rinsing program, you could try to also move the solvent inlet line in and out of the water bath several times, so that you can also get some air going through the line. This will help loosen any dirt or any of the valves by giving your rinsing action a little pulse.

You should pump at least 1-2 L of hot water through your system.

Once you are finished, you should rinse your system with ethanol. For this, you need to insert your solvent inline one into an ethanol bottle. I would recommend using the same rinsing program as before but changing your flow rate to 50 ml/min. Feel free to remove and re-insert the inline into the solvent bottle as before, with the goal of getting a bit of air to support your rinsing efforts. Rinse for about 2-3 minutes.

While the rinsing is going on, you can check your waste outlets and if you are achieving a constant solvent flow into the waste bottle. If yes, then everything is working as expected.

Issue 3: Pump is running, but no solvent at all flows through the pump

Solution: Here, we have a general failure at sucking in any solvent. To solve this problem, you need a piece of hose with the same dimensions as the inlet hose and a large syringe filled with a solvent such as ethanol. Again, we would need a rinsing program from the service option or manual control of your chromatography unit with a solvent flow rate of about 75 ml/min.

Now, you need to remove the inlet hose and connect your extra hose piece instead. Then insert syringe into your extra hose piece, hold firmly and inject solvent into the hose. This will generate overpressure and lead to solvent flow. Once you’ve achieved this, you can stop the pump and reconnect the line that comes from your flask. If all goes well, your pump should continue running again.

If you want to get some additional information on the flash pump, as well as visual guidance on how to solve solvent flow problems, check out this great video:

If you really got into the flow by now, you can also check out some nice theoretical background on chromatography, system components and other troubleshooting tips in the free guide, Chromapedia. And while we are on the subject of flow, check out one of the blog’s most popular posts on flow rate.

And our blog posts will keep flowing in as well! Keep dropping by, unimpeded and without any obstacles in your way to useful information on chromatography, rotary evaporation, and drying techniques!

Till next time,

The Signature of Bart Denoulet at Bart's Blog