Short path distillation — SPD — is one of those techniques that looks complicated but comes down to a pretty simple idea: heat your material under deep vacuum so that compounds evaporate at low temperatures, travel a very short distance to a cold condenser, and drip into separate collection flasks based on their boiling points. The short travel distance is what gives it the name, and it's what makes SPD so effective for purifying heat-sensitive compounds that would break down in conventional distillation setups.
What's actually in an SPD kit
A complete short path distillation setup has more parts than most people expect. Here's what you're working with:
The boiling flask holds your starting material and sits in a heating mantle. A magnetic stir bar keeps things moving inside to prevent hot spots.
The short path head is the centerpiece — it has the condenser built into it, which is why the vapor only travels a few inches before condensing. This is what makes SPD different from other distillation methods.
A heating mantle wraps around the boiling flask. You want a digital one with a PID controller because temperature precision is everything in SPD. A few degrees off and you're contaminating your target fraction with heads or tails.
Receiving flasks (usually 3-4) connect through a rotating "cow" adapter. As you increase temperature through the run, different compounds come over at different points. You rotate the cow to collect each fraction separately.
A vacuum pump that can pull deep vacuum — we're talking 50-500 microns, not the kind of vacuum you use for a vacuum oven. Two-stage rotary vane pumps are standard for SPD work.
A recirculating chiller pushes cold fluid through the condenser. For most SPD applications, you want the coolant at -10°C to -20°C.
And a cold trap between the SPD and the pump, because any vapor that sneaks past the condenser will trash your pump oil fast at these vacuum levels.
Picking the right size
2L kits are where most people start. They're affordable, they teach you the technique without a huge investment, and they handle small-batch R&D or testing runs just fine. If you're not sure SPD is right for your workflow, start here.
5L kits are the most popular size we sell for operations that have moved past the testing phase and are running regular production. Meaningful throughput, still manageable on a bench with a reasonable equipment footprint.
12L-20L kits are production equipment. Bigger boiling flasks, more powerful mantles, beefier pumps and chillers. These require experienced operators and a proper lab setup — but if you're processing serious volume, the efficiency gains are worth it.
The stuff nobody tells you before your first run
Degas your material first. Seriously. Dissolved gases in your starting material will cause violent bumping the moment you pull vacuum, and bumping sends crude material right up into your condenser and collection flasks. Warm your material gently with light stirring under mild vacuum for a few minutes before you start the real run.
Go slow on the temperature. Raise the mantle 5-10°C at a time and let it stabilize. Rushing creates bumping and cross-contamination between fractions. Patience pays off in purity.
Watch the vacuum gauge. When pressure suddenly ticks up, it usually means a new fraction is starting to come over. That's your cue to rotate the cow to a fresh flask.
Clean everything between runs. Residue from your last run will contaminate your next one. A solvent rinse on all glass parts takes five minutes and saves you from ruining a batch.
Write it all down. Temperatures, vacuum readings, fraction volumes, timing — record everything. You'll thank yourself when you need to reproduce a good run or troubleshoot a bad one.
Need help choosing a setup?
We carry complete SPD kits from 2L to 20L, plus individual replacement glassware and accessories. If you're trying to figure out what size and configuration makes sense for your operation, call us at (458) 836-8002 or email info@highdesertsci.com. We've helped a lot of people get their first SPD system dialed in.