8 Ways to Cool a GC Faster

There are few things I dislike more than wasting time and hanging around for a GC to cool is a time-wasting activity.

For arguments sake, let's say that you have a GC separation that takes 15 minutes with a cool-down time of 10 minutes, even when it is running samples flat out - your instrument will be unproductive 40% of the time. Now, say you were able to halve the cool-down time, your overall cycle time would drop from 25 to 20 minutes and you would make a productivity gain of 20%. For shorter separations, the gain will be even greater. Looking at this as an accountant might, in this example, the profitability of the analysis will also rise by 20% (which is a lot!) - more if there is a premium on getting results out quickly.

So minimising cool-down matters - even in an R&D environment since, by this example, you could get 20% more experiments done.

Unless you have already taken steps to address all of the following, there are certain improvements that you can make:-

1. Increase your oven start temperature - the lower the oven temperature, the slower it cools. Even if you end up increasing your oven start temperature by just a few degrees, this will add up to a huge saving over the course of the year.Use a higher phase ratio column - a means to achieving point 1, an increase in phase ratio can enable you to increase your start temperature by anything up to 20°C. You do however have to give regard to the fact that the later running components will elute later. This isn't always an option - but when it is, the benefits are great. Have your injector and detector no hotter than necessary - have you ever optimised this? The less energy you put into a GC, the less you have to get rid of during cool-down. Lower injector temperatures reduce sample degradation too.
2. Lower the lab temperature - I know of one lab where they use outdoor coats instead of lab coats and have the data systems in the (warmer) lab next door.
3. Make sure the GC's hot air exhaust cannot mix with incoming air. Have a good look around the back of your instrument - the recirculation of hot air will wreck an instruments cool-down performance.
4. Do not have your instruments back to back - a variation on point 5. If you have instruments on island benches, try to stagger them so that the hot air from one instrument is venting into a space between the instruments behind.
5. Vent the GC's hot air out of the room. Using the air conditioning system to remove this heat is very wasteful. It does not cost much to duct hot air out of the GC lab and the payback will be rapid - you will speed-up your work and reduce your energy bill as well.
6. Do not let your oven 'soak' at top temperature any longer than necessary - again the more energy you put in, the more you have to remove during cool-down.
7. Turn the lab temperature down before you leave each evening - OK, so you do not want to work in a ski-suit, but there is no reason why you can not run the lab cold overnight and at weekends.
8. Fit an Anatune GC CoolR+ - this is a powerful externally mounted fan that greatly increases the air flow through the GC oven. It will halve the cool-down time of an Agilent 6890 GC and save a third when used with the new 7890. Payback is a matter of weeks for instruments that are heavily used.

Many of these gains are synergistic and as GC run times get faster, the benefits will become even more significant.

Of the ideas listed above, 4, 5, 6 & 9 can be implemented now without having to re-validate your method. The others are best addressed during method development, indeed they are best addressed at the start of method development since they will make that process more efficient too.