I. Core Testing Indicators

The key evaluation dimensions of filtration efficiency include:

Particle retention rate: The percentage of particles of a specific size (such as 0.1-10 μm, covering the common particle sizes of aerosols) that are retained, is the most crucial indicator.

Aerosol cross-contamination prevention capability: Simulate the pipette's liquid aspiration and discharge process to verify whether the filter element can prevent aerosol reverse diffusion.

Liquid penetration resistance: The ability to prevent liquid backflow into the pipette, suitable for scenarios with viscous and easily foaming samples.

Ii. Common Detection Methods

1. Aerosol challenge Method (Industry mainstream, simulating real experimental pollution scenarios)

This is the most practical detection method. The steps are as follows:

Prepare the challenge substances: Select fluorescent microsphere suspensions (with particle sizes of 0.5 μm or 1.0 μm, easy to track) or bacterial aerosols (such as E. coli, suitable for microbiology laboratory scenarios) as the pollution sources.

Simulated pipetting operation: Install the pipette tip with a filter element on the pipette, repeatedly draw and discharge the suspension of the challenge substance, and simulate the continuous pipetting action in the experiment.

Interception effect detection

If fluorescent microspheres are used: After pipetting, disassemble the pipette piston and chamber, and observe with a fluorescence microscope whether there are any fluorescent particles remaining. Or detect the fluorescence intensity of the effluent and calculate the retention rate.

If bacterial aerosol is used: Inoculate the disassembled parts of the pipette onto the culture medium, observe the number of colonies after culture, and compare it with the control group without a filter core to evaluate the anti-contamination effect.

2. High Efficiency Particle Counter (HEPC) Method (Quantitative detection of particle retention rate)

It is suitable for precisely determining the filtration efficiency of filter elements for particles of different sizes, and the operation is more inclined towards physical and chemical testing

Equipment preparation: Use a high-efficiency particle counter, an aerosol generator, and a sealed test chamber.

Test process

The aerosol generator produces standard particle aerosols with known particle sizes (such as 0.1 μm, 0.3 μm, 1.0 μm) and concentrations.

Install the pipette tip filter element in the airflow channel of the test chamber and control the airflow to pass through the filter element at a speed that simulates the airflow velocity when the pipette draws liquid.

The particle concentrations at the upstream (air inlet end) and downstream (air outlet end) of the filter element were respectively detected by particle counters.