Today's rotary evaporators typically process multiple samples at once, but each sample needs to be processed independently of the other samples. Scientists need to make sure there is no cross-contamination. This requires careful control of airflow. Users also need to keep their systems in good shape. The importance of keeping needles clean cannot be overemphasized. If the pinhole is clogged, the hole will not dry out. In processes involving acids, the needles can corrode and become clogged. Some systems use stainless steel needles; others use PTFE, so choose the correct needle for your application. If a system includes a regulator, then that also needs to be maintained.
Boiling and foaming are common problems during evaporation that can lead to sample loss and contamination. The culprit is applying too much heat, too much spin speed or too much vacuum for a particular application. Collisions occur as the sample boils and bubbles rapidly, causing concentrated product to splash out of the container. Foaming, on the other hand, is caused by surfactants, which can be found in natural extracts as well as artificially made products. Foaming is slower than bubbling, and the foam tends to stay in the evaporating flask longer.
The traditional way to avoid collisions during evaporation is by visual inspection - simply watch the sample evaporator Incubator and adjust the vacuum pressure to avoid collisions. The bubble itself is unavoidable. It can only decrease. A common method of reducing foam is to open and close the stopcock when foam occurs. Another way to reduce the problem is to apply the vacuum slowly. "
With these methods, several products are available that reduce sample loss and contamination when swelling and foaming occurs, help to completely eliminate swelling and better reduce foaming. To specifically address foaming, defoamers, large-capacity flasks, or specialized glass condensers can be used, which provide more room for the foam to expand. A simple glass foam stopper can help prevent foam from entering the receiving bottle. A bump trap, which is a second flask that is smaller than the main flask, is also often used during evaporation. This additional flask is placed just above the main flask so that if a jolt occurs, the sample will be trapped in the jolt trap before being sucked into the rest of the rotary evaporator or condenser. Lining the anti-collision wells does not reduce collisions, but it prevents sample loss.
The vacuum controller was getting closer to the source of the problem. By controlling the speed of the pump, these devices can greatly reduce or eliminate the possibility of collisions. An automatic function can be used to sense the vapor pressure of the solvent and use it as a set point. Then there's the foam sensor, which detects the foam inside the evaporator bottle and inflates the system slightly to ensure the foam bursts. The foam sensor allows automatic, unattended distillation of foam samples.
