A freeze dryer, or lyophilizer, is used to preserve samples by removing moisture from them via sublimation, which is a direct phase change from a solid to a gas. Dry ice being exposed to normal ambient temperature is a great example of this phenomenon.
Freeze dryers are used in many different disciplines, from preserving fragile archaeological artifacts to extending the shelf-life of fruit and vegetables. Their most common application in laboratories is preserving organic samples, like blood, that have yet to be analyzed.
How Does a Lab Freeze Dryer Work?
Lyophilizers, or freeze dryers, work by forcing the solvent (the substance that the sample is suspended in) to sublimate directly into vapor, thus skipping the liquid phase. Samples can be preserved very well, as no chemical bonds are broken or formed in the process. This makes freeze drying a vital process in many applications, especially research applications.
According to Labconco, one of the largest manufacturers of laboratory freeze dryers, samples undergoing lyophilization are put through three stages: pre-freezing, sublimation (or primary drying), and adsorption (or secondary drying). Let's dive into the details of each stage.
Pre-Freezing
As its name suggests, the first step in the lyophilization process prepares the samples for sublimation. This is achieved by cooling the samples down past the melting point of the solvent (that which the sample is dissolved in) to ensure that they are completely frozen. Otherwise, the samples will be damaged during primary drying. This makes pre-freezing is a vital part of the lyophilization process.
Sublimation (Primary Drying)
Once the sample is completely frozen, the second stage of lyophilization, primary drying, can begin.
The main objective here is to remove the ice from the sample. Sublimation removes ice from the frozen sample to create a dry and structurally intact product. The two important factors to control in this process are pressure and temperature.
First, the vacuum pump is powered on and begins pulling a vacuum in the sample chamber, which lowers both the chamber's pressure and, in turn, the sample's boiling point. The vacuum pump also helps to promote the free flow of water molecules from the sample.
The sample is then heated (either through ambient heat transfer from the environment or through a heat source built into the chamber; manifold dryers employ ambient heating while shelf dryers use a physical heat source), thus sublimating the solvent. Heat has to be applied to help remove the water from the sample in the form of water vapor.
Without lowering the pressure within the sample chamber, it'd be virtually impossible to skip the liquid phase, as the sample's boiling point would be much higher.
The collecting system, which is a cold trap that collects moisture removed from the sample, works alongside the vacuum pump.
Adsorption (Secondary Drying)
The final stage in the lyophilization process is adsorption, secondary drying, or post-drying. Primary drying only removes up to 93% of the sample's moisture, so secondary drying evaporates the residual moisture, making the sample sufficiently dry for storage or study.
What Types of Freeze Dryers Are There?
Freeze dryers are unique machines in that they have a place in so many different settings. There are consumer-level models used in home kitchens to preserve food, massive industrial-grade systems used in manufacturing processes, and finally there's the type we offer: research-focused laboratory models that, in terms of throughput, fall between home units and industrial units. Since we specialize in laboratory models, we'll focus on the variations in that category.
Each of these freeze dryers can be bought new or used. The main difference here is price, with used models being more cost-effective if you have a tighter budget. You can rest assured that your used freeze dryer performs at high performance by sourcing your instrument from a trusted used lab equipment dealer.
Manifold Freeze Dryers
Perhaps the most popular choice, manifold dryers make use of stainless steel manifolds, flasks, and valves to sublimate samples. When using a manifold dryer, users first pre-freeze their samples in glass flasks. They then attach the flasks to the valves branching off the manifold, initiate the sublimation process, and simply detach the flasks when the process is finished.
There are two main types of manifolds: tree, and drum. Tree manifolds are better suited for high-throughput applications, while drum manifolds save more space.
Most manifold dryers are modular. You can easily swap the manifolds out so they can always use the format that best suits their current application.
Manifold freeze dryers are ideal for labs that only need to freeze dry a small number of samples. As such, they're best used for research rather than in commercial applications.
Shelf Freeze Dryers
Shelf freeze dryers have integrated sublimation chambers with, you guessed it, shelves. Typically, these shelves are adjustable so users can fit sample containers of varying sizes in.
Shelf dryers are often used to develop freeze drying "recipes", or reproducible procedures with defined parameters for temperature, pressure, duration, etc. These systems are useful for development because they're designed to work with more precise parameters than manifold dryers. Because they can achieve such precision, shelf dryers are frequently used to process samples of especially low volumes since they're so sensitive.
Combination Freeze Dryers
Featuring both shelves and valves, combination freeze dryers allow users to have the best of both worlds. These systems are suited for labs that must address varying lyophilization needs while remaining budget-conscious.
Benefits of Freeze Drying in Labs
There are many reasons why freeze drying in labs can be beneficial, including:
- Increased stability: Once freeze-dried, samples are often more stable. This is useful in immunoengineering products such as vaccines, which need to be shipped around and stored at scale while making sure they are still safe to administer in terms of quality and efficacy.
- No refrigeration: Freeze-dried samples can be stored at room temperature, which allows for easier storage and transport.
- Cost: While the initial outlay for a freeze dryer can be a large investment, savings can be achieved in the long term because you don't have to stabilize the samples through refrigeration.
- Better virus detection: When used in wastewater detection of coronavirus, freeze drying was more effective at detecting infected samples, more flexible to store and meant less exposure risks to labor.
The Anatomy of a Freeze Dryer
So, what does a freeze dryer need to work? Let's go over some of the most vital components:
- Vacuum pump: As mentioned earlier, the vacuum pump pulls a vacuum within the sample chamber to lower its boiling point. Without a strong vacuum, sublimation would require much more energy.
- Sample chamber: This is either a flask or a chamber filled with shelves in which the sample sits as it undergoes lyophilization.
- Condenser: The condenser re-freezes the water vapor released during sublimation, turning it back into ice so it can be easily removed from the freeze dryer.
Maintaining a Freeze Dryer
Keeping a lyophilizer running smoothly can be tricky. Here are some tried and true methods for freeze dryer maintenance to follow:
- Change your vacuum oil regularly.
- Use water or water-based solutions to clean the door gasket.
- Place your freeze dryer at a safe distance from the wall.
- Clean your freeze dryer often to clear away any residue.
- Use a dust cover to protect your freeze dryer from airborne particles.
- Ensure the condenser has dropped the chamber temperature before turning on the vacuum pump.
Find a Laboratory Freeze Dryer for Your Needs at New Life Scientific
A freeze dryer is a powerful tool in any laboratory. They are used across many disciplines to achieve all the benefits of the lyophilization process, in making samples more stable and portable. Freeze dryers do this by carefully removing the water or solvent from a product at a low temperature, which preserves its functionality. You can reduce the initial outlay cost of buying a freeze dryer by purchasing a used one instead. When you buy used equipment from New Life Scientific, you can save 35% to 95% off new retail prices, and every purchase is backed by our 90-day warranty.
Founded in 2014, New Life Scientific helps the life science community by selling affordable, quality used lab instruments. Browse our catalog of freeze dryers and view our FAQ guide for purchasing a freeze dryer. Need more help? Contact us at 567-292-2752 or fill out a form online.
