Fig. 1: Distimatic with rotary evaporator inside a fume hood
The COVID-19 crisis and the resulting increased demand for disinfectants such as isopropanol or ethanol have already led to bottlenecks in some regions and to a rise in solvents prices on the world market. Therefore, solvent recycling is not only a sustainable but also a considerable way of reducing operating costs in the own laboratory and at the same time increasing efficiency.
Solvent recovery by means of an evaporation process is a common laboratory work process, for which often a rotary evaporator is used. Even if this is a suitable and sample-conserving lab device for this process, the manual operation (the so-called batch operation) is less than efficient, in particular, if larger solvent volumes have to be purified.
Evaporating flasks only hold a limited volume and must be refilled or replaced, which leads to long heating times of the cold medium before the process starts again. The capacity of receiving flasks is also limited and requires regular emptying during operation. To do this, the entire system must be ventilated and a running process must be stopped. Evaporation in batch operation is a dynamic process during which the conditions in the entire system are constantly changing. In addition, the vacuum has to be manually readjusted several times in order to achieve a consistently high performance. Consequently, a laboratory employee is often busy for several minutes adjusting the process parameters, filling and emptying the flasks or changing them if necessary. This is a cost factor that reduces the possible savings.
Hundreds of customers worldwide have already achieved a significant efficiency increase in solvent recycling by using an automated module that independently controls the filling and emptying of the evaporator and receiving flasks. The University of Bayreuth (Germany) provides us with a concrete example for this increase in efficiency. At the labs of the Faculty of Macromolecular Chemistry, very small quantities with similar contents were very often evaporated, as usual in chemistry laboratories. The doctoral students and laboratory assistants working in this laboratory spent a significant amount of time performing the typical work steps on the rotary evaporator in order to purify small amounts of a few hundred milliliters of solvents.
Mr. Lothar Benker, responsible for the equipment pool in this work group, recognized the potential of automation and instructed the doctoral students in the respective work group to collect the small quantities into 5 to 20-liter containers and not to bother with manual processing. The new workflow established is designed in such manner that at the end of the working day, the Heidolph system of the Distimatic automatic module and rotary evaporator (Fig. 1) is switched on and one of the containers filled during the day is automatically processed overnight without supervision. The next morning, the doctoral students find the separated liquids ready for use, which are then immediately available for further use in the laboratory. Mr. Benker estimates that now, his doctoral students have an additional hour for research per day per employee.