Should I use a flask or tray freeze dryer?
Generally, the type of samples you intend to freeze dry will determine which type of lyophilizer you should purchase. Tray dryers are best suited for small samples with a low amount of moisture, like when you're using microplates. Flask dryers are used when the sample in question has a lot of moisture to be evaporated and isn't particularly small.
There are other factors to consider, however. For instance, tray freeze dryers are known to have more precise settings for the different parameters of a recipe. This makes them ideal for recipe development and testing, or for processing particularly sensitive samples. Conversely, flask dryers are better for labs that are doing routine freeze drying with more forgiving samples.
Do I need a shell bath for pre-freezing?
The main purpose a shell bath is to quicken the lyophilization process by freezing a sample around the interior of the flask, which increases its surface area and allows it to evaporate faster. If you need to process samples with quick turnaround time, then a shell bath may be for you.
Should I get a floor or benchtop freeze dryer?
The amount of free space you have, along with the condenser capacity you need, are the key considerations for this question. If you're running low on floorspace and have no need for a condenser over 6 liters or so, then you should opt for a benchtop lyophilizer. Floor models are best suited for those with the space to hold them and the sample load to justify larger condensers.
How frequently should I change vacuum pump oil?
There is no hard and fast rule for how frequently one should change their vacuum pump oil. A good rule of thumb, however, is that harsher, more acidic samples will warrant changes more frequently than gentler, aqueous samples. Ultimately, you should change the oil at least once every few weeks. If you notice that your freeze dryer has trouble maintaining a strong vacuum, consider changing the pump oil more frequently.
Which brand of freeze dryer should I buy?
In general, any freeze dryer from an established company whose specifications suit your requirements will suffice. However, some of the major manufacturers — namely, SP Scientific and Labconco — clearly appeal to different buyers.
SP Scientific, who owns VirTis, produce robust, easy-to-maintain, high-capacity freeze dryers best suited for routine lyophilization in industrial settings. While they aren't the most sophisticated systems, they're true workhorses that can handle large sample loads.
Conversely, Labconco manufactures research-oriented dryers. These systems aren't quite as tough as VirTis units, nor are their capacities as large. (Fun fact: the largest Labconco dryer has only an 18 liter condenser, while SP Scientific sells dryers with condensers as large as 50 liters.) However, Labconco systems also have more sophisticated onboard software that make them excellent for recipe development and processing highly sensitive samples.
What are the advantages of buying a new freeze dryer?
Current-gen freeze dryers excel at data management and monitoring. Many of them have special software, such as Labconco's Lyo-Works OS, that allow remote monitoring, multi-step custom programs, data visualization, and more. Such features are considerably less common among the freeze dryers populating the used market. So, if you have particularly sensitive samples and must prioritize in-depth monitoring, data collection, etc., then purchasing a brand-new, current-gen freeze dryer may be your best bet.