Evaporation Rate Control on a rotovap evaporator

The evaporation rate on rarotovap evaporator is critical to effectively remove the solvent and preserve the sample. The following are key factors controlling the evaporation rate on a rotovap evaporator:

1. Temperature – The water bath temperature directly affects evaporation. Higher temperatures increase the evaporation rate but may degrade properties of heat-sensitive compounds. Typically, the water bath temperature is set 10-20°C below the boiling point of the solvent.

2. Vacuum Pressure – Lowering the pressure lowers the boiling point of the solvent. Use a vacuum pump or aspirator to adjust the pressure. Higher vacuum levels increase the evaporation rate but may cause bumping. Use a vacuum gauge to monitor.

3. Speed – Higher speeds increase the surface area of ​​the sample film, which enhances evaporation. However, too fast a speed may cause splashing. The optimum speed is typically 150-250 RPM.

4. Cooling Efficiency – The condenser must effectively capture the evaporated solvent. Ensure that the coolant (e.g. dry ice/acetone or chilled water) is circulating properly to maintain low temperatures.

5. Solvent volume and flask size – Avoid overfilling the flask (≤ 50% of capacity) to prevent bumping. Larger flasks may slow evaporation due to reduced film thickness.

6. Bumping control – Use zeolites or anti-bumping pellets to ensure smooth evaporation. Alternatively, if bumping occurs, slowly increase the vacuum or lower the bath temperature.

By balancing these parameters on your rotovap evaporator, you can optimize the evaporation rate while ensuring the integrity of your sample. Always monitor the evaporation process closely to avoid overheating or solvent loss.