Trap Balls

One of the most common problems encountered during concentration with a rotary evaporator is bumping.
A trap ball helps minimize the impact of bumping by preventing sample from entering the condenser and vacuum system. Here, we introduce the purpose and benefits of trap balls, as well as how to select the right one for your application.

What is a trap ball?

A trap ball is a glassware accessory designed to prevent the sample from overflowing into the receiving flask or condenser due to sudden “bumping”, thereby avoiding sample loss.

When a rotary evaporator is placed under vacuum, the boiling point of the sample in the sample flask (pear shaped flask) drops sharply. This can cause “bumping,” a phenomenon where vaporization cannot keep pace with the pressure drop, leading to sudden, violent boiling. When bumping occurs, the valuable sample is forcefully ejected, traveling with the vapor into the condenser or receiving flask.

This can lead to issues such as:

• Failed concentration, resulting in sample loss and the need to restart the process
• Time-consuming cleanup of the condenser and receiving flask
• Vacuum pump failure, as sample may enter the vacuum line

Over 60% of rotary evaporator users rely on a trap ball

▶▶▶ Bumping in a rotary evaporator

How to prevent bumping (and What to do when it happens)

While measures can be taken to prevent bumping—such as using the vacuum ramp program on a vacuum controller—it cannot always be completely avoided. This is where a trap ball comes in. If unexpected bumping occurs, the trap ball catches the splashed sample, preventing it from entering the receiving flask. Furthermore, as long as the trap ball is kept clean, the valuable sample can be recovered and returned to the sample flask to continue concentration. In addition, a trap ball can also serve as an adapter when the joint sizes of the rotary joint and the sample flask do not match.

How to select a trap ball

1. Choose the joint size that matches the rotary joint of your rotary evaporator.
   
   EYELA rotary joints are available in two joint sizes: TS29/38 (standard set) and TS24/40. Check your rotary joint and choose the joint size for A.
   
   Next, choose the joint size for B, which corresponds to the sample flask (pear shaped flask) you are using. We offer four sizes: TS29/38, TS24/40, TS19/38, and TS15/25. Always be sure to choose a trap ball that matches your joint size.
   
2. Next, choose the capacity (C) of a trap ball. A good rule of thumb is to select a capacity that is about 1/2 of the sample flask (pear shaped flask) capacity.
   
   For example, when using a 500mL sample flask (pear shaped flask), the maximum sample volume is half of that, which is 250mL. The guideline is to choose a capacity that can catch the entire 250mL sample in the trap ball even if it bumps. In this case, we recommend a trap ball with a capacity of 300mL or 200mL.
   
3. Resin-coated trap balls are also available, which are shatter-resistant and designed to prevent scattering even if broken.