Let’s match a vapor duct to your rotary evaporation application

If you haven’t given a duck about your vapor duct until now, maybe it is a good time to start. The vapor duct might be a small piece, but its importance in the rotary evaporation process should not be underestimated. Here, I present three cases and explain how to find the most suitable vapor duct for your particular application.

Last week I had the luxury of finally going to the hairdresser. After a year of my poor wife having to do the job, I was very happy to let a professional take a jab at my hair. Next to me in the hair salon was a young lady getting a very complicated do. The hairdresser was spinning around in circles using round brushes, skinny brushes, brushes with holes in them and combs all the while blow drying her customer’s hair into more volume, curls and straight parts needed to produce the final masterpiece.

As captivated as I was by all the tools of the hairdresser’s trade, I couldn’t help but compare her experience to our own in the laboratory. We, scientists, are also heavily dependent on specialized tools and accessories for different applications.

I mean, it would be quite challenging to make a side part in the hair with a brush instead of a comb. And in the lab? Well, for example, it can be just as difficult to achieve optimal rotary evaporation performance if you are using the incorrect vapor duct for your purpose.

You might laugh at a whole blog post dedicated to vapor ducts, but why not? After all, the vapor duct serves as the axis for the rotation of your sample, and as a vacuum-tight channel for vapor getting drawn off your sample. Hence, this little glass piece lies in the heart and soul of your process.

vapor duct, analytical vapor duct, rotary evaporation, laboratory evaporation

So let me walk you through a few common rotary evaporation applications and you can see if you are using the ideal vapor duct for your needs.

1. Analytical applications – If you are working on analytical experiments, then your rotary evaporation system would benefit from an analytical vapor duct. These ducts are slightly longer than standard ones. When the vapor duct is longer, even if we have solvent on the seal, we will prevent any solvent from flowing back into the evaporating flask.

2. Solid samples – If you are processing solid samples, such as powder, then I would recommend the use of frit vapor ducts. These are quite similar to standard ones, except for the existence of a frit in one opening of the duct. This feature helps prevent powders from leaving the evaporation flask and reaching the condenser.

3. High-temperature applications – If you are handling very hot samples, such as bitumen, then you might benefit from some plastic protection. In this case, the ideal vapor duct is the same length and same diameter as a regular one, but it has a plastic piece wrapped around the center. This expensive plastic material enables you to easily remove the vapor duct from the motor without suffering any discomfort from high heat.

If you’d like to see how all these vapor ducts look like and you’ve got about 1:50 minutes to spare, take a look at the video below:

Now, no matter what kind of a vapor duct you end up using, I would also recommend looking for features that simplify handling of the evaporation flask and the duct. For example, a mechanism, such as the CombiClip, not only holds the flask in place and simplifies pushing the flask off whenever necessary, you can also use it for vapor duct removal. Such features make your process easier and safer.

If you’ve had enough of this topic and would like to duck anymore conversation revolving around vapor ducts, I would suggest focusing on the bigger picture. What comes immediately to my mind is if you’ve got your entire rotary evaporation system configured correctly. Feel free to read more on this subject in my previous blog post on rotary evaporation configuration .

I hope you don’t find I’m cutting this post short or brushing any parts of the topic aside. If you’d like more information on vapor ducts, leave me a comment below. If not, drop by again anyway to see what exciting topics in chromatography and rotary evaporation I will explore next.

Till next time,

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